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The future of the AA filter
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RichA
Feb 7, 2012, 8:47:16 AM2/7/12
to
Nikon is offering a model D800E without it, the new pro Fuji doesn't
have one, the Leica M9 (I think) doesn't have one and Olympus
supposedly is using a very weak one on the new OM-D. The Fuji is the
odd man out here owing to its sensor configuration. If they come out
with a revolutionary new sensor design, maybe the AA thing will be
moot, but it's interesting see it's dominance waning a bit now.
have one, the Leica M9 (I think) doesn't have one and Olympus
supposedly is using a very weak one on the new OM-D. The Fuji is the
odd man out here owing to its sensor configuration. If they come out
with a revolutionary new sensor design, maybe the AA thing will be
moot, but it's interesting see it's dominance waning a bit now.
Bruce
Feb 7, 2012, 8:59:16 AM2/7/12
to
Think of the billions of mushy images that have been made in the last
eight years using DSLRs with AA filters with fine detail smeared
beyond recognition. All because of an irrational fear of aliasing and
moire. It is a monumental waste of talent and of good equipment that
has been unnecessarily degraded.
Our pre-orders for the Nikon D800/800E are split about 60/40 with the
greater number choosing the version *with* the AA filter. You can
lead a horse to water, but you cannot make it drink. ;-)
Floyd L. Davidson
Feb 7, 2012, 10:49:31 AM2/7/12
to
--
Floyd L. Davidson <http://www.apaflo.com/>
Ukpeagvik (Barrow, Alaska) fl...@apaflo.com
RichA
Feb 7, 2012, 12:56:40 PM2/7/12
to
On Feb 7, 10:49 am, fl...@apaflo.com (Floyd L. Davidson) wrote:
> Bruce <docnews2...@gmail.com> wrote:
today's standards) megapixel count show definite sharpness and detail
improvements. There are sites that show this. I even noticed it on
an old D100 I converted for IR work.
> Bruce <docnews2...@gmail.com> wrote:
> >RichA <rander3...@gmail.com> wrote:
>
> >>Nikon is offering a model D800E without it, the new pro Fuji doesn't
> >>have one, the Leica M9 (I think) doesn't have one and Olympus
> >>supposedly is using a very weak one on the new OM-D. The Fuji is the
> >>odd man out here owing to its sensor configuration. If they come out
> >>with a revolutionary new sensor design, maybe the AA thing will be
> >>moot, but it's interesting see it's dominance waning a bit now.
>
> >My Kodak DCS Pro 14n didn't have one either. That was made in 2004.
>
> >Think of the billions of mushy images that have been made in the last
> >eight years using DSLRs with AA filters with fine detail smeared
> >beyond recognition. All because of an irrational fear of aliasing and
> >moire. It is a monumental waste of talent and of good equipment that
> >has been unnecessarily degraded.
>
> >Our pre-orders for the Nikon D800/800E are split about 60/40 with the
> >greater number choosing the version *with* the AA filter. You can
> >lead a horse to water, but you cannot make it drink. ;-)
>
> You have an astonishing lack of technical acumen.
>
The proof is in the pudding. Converted D200s with a modest (by
>
> >>Nikon is offering a model D800E without it, the new pro Fuji doesn't
> >>have one, the Leica M9 (I think) doesn't have one and Olympus
> >>supposedly is using a very weak one on the new OM-D. The Fuji is the
> >>odd man out here owing to its sensor configuration. If they come out
> >>with a revolutionary new sensor design, maybe the AA thing will be
> >>moot, but it's interesting see it's dominance waning a bit now.
>
> >My Kodak DCS Pro 14n didn't have one either. That was made in 2004.
>
> >Think of the billions of mushy images that have been made in the last
> >eight years using DSLRs with AA filters with fine detail smeared
> >beyond recognition. All because of an irrational fear of aliasing and
> >moire. It is a monumental waste of talent and of good equipment that
> >has been unnecessarily degraded.
>
> >Our pre-orders for the Nikon D800/800E are split about 60/40 with the
> >greater number choosing the version *with* the AA filter. You can
> >lead a horse to water, but you cannot make it drink. ;-)
>
> You have an astonishing lack of technical acumen.
>
today's standards) megapixel count show definite sharpness and detail
improvements. There are sites that show this. I even noticed it on
an old D100 I converted for IR work.
Floyd L. Davidson
Feb 7, 2012, 6:09:07 PM2/7/12
to
said any better than he understands the technical
aspects he discussed.
The D100, with only 6 MP, produced very nice pictures.
Even though it has an anti-aliasing filter. You can
"Think of the billions of mushy images that have been
made in the last eight years using DSLRs with AA filters
with fine detail smeared beyond recognition." or you can
made in the last eight years using DSLRs with AA filters
imagine how nice the pictures will be with six times as
many pixels!
Take away the anti-aliasing filter, with either a 6 MP
camera or a 36 MP camera, and then the pictures *do* have
"mushy" artifacts generated by sampling data above the
Nyquist Limit. Comparing images from a 36 MP camera
without the filter to images from a 6 MP camera with the
filter, and often the 6 MP image will have better
detail!
Rich
Feb 7, 2012, 8:57:10 PM2/7/12
to
fl...@apaflo.com (Floyd L. Davidson) wrote in
news:87lioed...@apaflo.com:
Do you honestly want to see that comparison?
news:87lioed...@apaflo.com:
Floyd L. Davidson
Feb 8, 2012, 1:46:25 AM2/8/12
to
nospam
Feb 8, 2012, 10:17:24 AM2/8/12
to
In article <i6b2j7lh241vua9nq...@4ax.com>, Bruce
aliasing artifacts.
> Think of the billions of mushy images that have been made in the last
> eight years using DSLRs with AA filters with fine detail smeared
> beyond recognition. All because of an irrational fear of aliasing and
> moire. It is a monumental waste of talent and of good equipment that
> has been unnecessarily degraded.
nonsense. there are not billions of such images.
> Our pre-orders for the Nikon D800/800E are split about 60/40 with the
> greater number choosing the version *with* the AA filter. You can
> lead a horse to water, but you cannot make it drink. ;-)
how ironic. you've been led to the facts about aliasing and sampling
theory, but yet you still refuse to believe any of it, clinging to this
idiotic notion of antialiasing filters causing mush.
if you're getting mush, you are doing something wrong or your camera is
defective. it's not due to an aa filter.
<docne...@gmail.com> wrote:
> >Nikon is offering a model D800E without it, the new pro Fuji doesn't
> >have one, the Leica M9 (I think) doesn't have one and Olympus
> >supposedly is using a very weak one on the new OM-D. The Fuji is the
> >odd man out here owing to its sensor configuration. If they come out
> >with a revolutionary new sensor design, maybe the AA thing will be
> >moot, but it's interesting see it's dominance waning a bit now.
>
> My Kodak DCS Pro 14n didn't have one either. That was made in 2004.
and its users complained about the 'italian flag syndrome,' aka,
> >Nikon is offering a model D800E without it, the new pro Fuji doesn't
> >have one, the Leica M9 (I think) doesn't have one and Olympus
> >supposedly is using a very weak one on the new OM-D. The Fuji is the
> >odd man out here owing to its sensor configuration. If they come out
> >with a revolutionary new sensor design, maybe the AA thing will be
> >moot, but it's interesting see it's dominance waning a bit now.
>
> My Kodak DCS Pro 14n didn't have one either. That was made in 2004.
aliasing artifacts.
> Think of the billions of mushy images that have been made in the last
> eight years using DSLRs with AA filters with fine detail smeared
> beyond recognition. All because of an irrational fear of aliasing and
> moire. It is a monumental waste of talent and of good equipment that
> has been unnecessarily degraded.
> Our pre-orders for the Nikon D800/800E are split about 60/40 with the
> greater number choosing the version *with* the AA filter. You can
> lead a horse to water, but you cannot make it drink. ;-)
theory, but yet you still refuse to believe any of it, clinging to this
idiotic notion of antialiasing filters causing mush.
if you're getting mush, you are doing something wrong or your camera is
defective. it's not due to an aa filter.
nospam
Feb 8, 2012, 10:17:25 AM2/8/12
to
In article
<204668f0-1aec-4cd4...@m2g2000vbc.googlegroups.com>,
sharpness improvements.
<204668f0-1aec-4cd4...@m2g2000vbc.googlegroups.com>,
RichA <rande...@gmail.com> wrote:
> The proof is in the pudding. Converted D200s with a modest (by
> today's standards) megapixel count show definite sharpness and detail
> improvements. There are sites that show this. I even noticed it on
> an old D100 I converted for IR work.
what you noticed were aliasing artifacts and false detail, not
> The proof is in the pudding. Converted D200s with a modest (by
> today's standards) megapixel count show definite sharpness and detail
> improvements. There are sites that show this. I even noticed it on
> an old D100 I converted for IR work.
sharpness improvements.
nospam
Feb 8, 2012, 10:17:26 AM2/8/12
to
In article <SbydnbnQneDrS6zS...@giganews.com>, Rich
bring it on. you obviously don't understand what it is you're looking
at. if you remove the aa filter, you *will* get artifacts unless there
isn't much detail to begin with (e.g., a solid colour wall).
bring it on. you obviously don't understand what it is you're looking
at. if you remove the aa filter, you *will* get artifacts unless there
isn't much detail to begin with (e.g., a solid colour wall).
RichA
Feb 8, 2012, 11:30:13 AM2/8/12
to
On Feb 8, 10:17 am, nospam <nos...@nospam.invalid> wrote:
> In article
> <204668f0-1aec-4cd4-bfb3-319af4e51...@m2g2000vbc.googlegroups.com>,
be visible?
> In article
> <204668f0-1aec-4cd4-bfb3-319af4e51...@m2g2000vbc.googlegroups.com>,
>
> RichA <rander3...@gmail.com> wrote:
> > The proof is in the pudding. Converted D200s with a modest (by
> > today's standards) megapixel count show definite sharpness and detail
> > improvements. There are sites that show this. I even noticed it on
> > an old D100 I converted for IR work.
>
> what you noticed were aliasing artifacts and false detail, not
> sharpness improvements.
So you are willing to state that no additionally resolved detail would
> RichA <rander3...@gmail.com> wrote:
> > The proof is in the pudding. Converted D200s with a modest (by
> > today's standards) megapixel count show definite sharpness and detail
> > improvements. There are sites that show this. I even noticed it on
> > an old D100 I converted for IR work.
>
> what you noticed were aliasing artifacts and false detail, not
> sharpness improvements.
be visible?
RichA
Feb 8, 2012, 11:36:32 AM2/8/12
to
On Feb 8, 10:17 am, nospam <nos...@nospam.invalid> wrote:
> In article <SbydnbnQneDrS6zSnZ2dnUVZ_uGdn...@giganews.com>, Rich
>
> <n...@nowhere.com> wrote:
> > Do you honestly want to see that comparison?
>
> bring it on. you obviously don't understand what it is you're looking
> at. if you remove the aa filter, you *will* get artifacts unless there
> isn't much detail to begin with (e.g., a solid colour wall).
Even if it is the case that no additional detail was gained, the mere
> <n...@nowhere.com> wrote:
> > Do you honestly want to see that comparison?
>
> bring it on. you obviously don't understand what it is you're looking
> at. if you remove the aa filter, you *will* get artifacts unless there
> isn't much detail to begin with (e.g., a solid colour wall).
ability to be able to increase sharpness without inducing edge
artifacting that you see on normal AA filtered images when too much
sharpness is applied is a good enough reason to switch to an AA-less
camera. I agree, sharpness increases do not always = detail
increases, but clean sharpness increases are always desirable,
especially if you are making larger prints, or cropping.
http://maxmax.com/nikon_d200hr.htm
nospam
Feb 8, 2012, 11:49:35 AM2/8/12
to
In article
<8df03917-9322-43c9...@hs8g2000vbb.googlegroups.com>,
said, you don't understand what it is you're looking at.
> I agree, sharpness increases do not always = detail
> increases, but clean sharpness increases are always desirable,
> especially if you are making larger prints, or cropping.
>
> http://maxmax.com/nikon_d200hr.htm
they're selling something, so obviously they're going to try to paint a
rosy picture. the funny thing is they even say it's worse:
Notice that the HR models clearly shows some banding and color moiré
problems.
<8df03917-9322-43c9...@hs8g2000vbb.googlegroups.com>,
RichA <rande...@gmail.com> wrote:
> > > Do you honestly want to see that comparison?
> >
> > bring it on. you obviously don't understand what it is you're looking
> > at. if you remove the aa filter, you *will* get artifacts unless there
> > isn't much detail to begin with (e.g., a solid colour wall).
>
> Even if it is the case that no additional detail was gained, the mere
> ability to be able to increase sharpness without inducing edge
> artifacting that you see on normal AA filtered images when too much
> sharpness is applied is a good enough reason to switch to an AA-less
> camera.
no it isn't and you can add the sharpness in the processing. like i
> > > Do you honestly want to see that comparison?
> >
> > bring it on. you obviously don't understand what it is you're looking
> > at. if you remove the aa filter, you *will* get artifacts unless there
> > isn't much detail to begin with (e.g., a solid colour wall).
>
> Even if it is the case that no additional detail was gained, the mere
> ability to be able to increase sharpness without inducing edge
> artifacting that you see on normal AA filtered images when too much
> sharpness is applied is a good enough reason to switch to an AA-less
> camera.
said, you don't understand what it is you're looking at.
> I agree, sharpness increases do not always = detail
> increases, but clean sharpness increases are always desirable,
> especially if you are making larger prints, or cropping.
>
> http://maxmax.com/nikon_d200hr.htm
rosy picture. the funny thing is they even say it's worse:
Notice that the HR models clearly shows some banding and color moiré
problems.
nospam
Feb 8, 2012, 11:50:20 AM2/8/12
to
In article
<6a194f23-673a-46f2...@c6g2000vbk.googlegroups.com>,
what you get are artifacts, or false detail, which occasionally might
look ok, but most of the time it will be a problem.
<6a194f23-673a-46f2...@c6g2000vbk.googlegroups.com>,
RichA <rande...@gmail.com> wrote:
> > > The proof is in the pudding. Converted D200s with a modest (by
> > > today's standards) megapixel count show definite sharpness and detail
> > > improvements. There are sites that show this. I even noticed it on
> > > an old D100 I converted for IR work.
> >
> > what you noticed were aliasing artifacts and false detail, not
> > sharpness improvements.
>
> So you are willing to state that no additionally resolved detail would
> be visible?
no details that were not originally in the subject.
> > > The proof is in the pudding. Converted D200s with a modest (by
> > > today's standards) megapixel count show definite sharpness and detail
> > > improvements. There are sites that show this. I even noticed it on
> > > an old D100 I converted for IR work.
> >
> > what you noticed were aliasing artifacts and false detail, not
> > sharpness improvements.
>
> So you are willing to state that no additionally resolved detail would
> be visible?
what you get are artifacts, or false detail, which occasionally might
look ok, but most of the time it will be a problem.
Bruce
Feb 8, 2012, 3:57:17 PM2/8/12
to
I would be willing to bet that the vast majority of those who
pontificate at length about aliasing and moire have zero or near-zero
experience of using DSLRs that don't have AA filters.
Their arguments are simply theoretical and not based on practical
considerations.
nospam
Feb 8, 2012, 4:11:34 PM2/8/12
to
In article <48o5j710r3i1eve6m...@4ax.com>, Bruce
> I would be willing to bet that the vast majority of those who
> pontificate at length about aliasing and moire have zero or near-zero
> experience of using DSLRs that don't have AA filters.
>
> Their arguments are simply theoretical and not based on practical
> considerations.
practical considerations are that kodak users constantly produce images
with aliasing and then complain about the italian flag syndrome. you're
the only one who claims it doesn't happen.
<docne...@gmail.com> wrote:
> >> > The proof is in the pudding. Converted D200s with a modest (by
> >> > today's standards) megapixel count show definite sharpness and detail
> >> > improvements. There are sites that show this. I even noticed it on
> >> > an old D100 I converted for IR work.
> >>
> >> what you noticed were aliasing artifacts and false detail, not
> >> sharpness improvements.
> >
> >So you are willing to state that no additionally resolved detail would
> >be visible?
>
> I think it is self-evident that he is willing to talk nonsense.
you misspelled 'facts'.
> >> > The proof is in the pudding. Converted D200s with a modest (by
> >> > today's standards) megapixel count show definite sharpness and detail
> >> > improvements. There are sites that show this. I even noticed it on
> >> > an old D100 I converted for IR work.
> >>
> >> what you noticed were aliasing artifacts and false detail, not
> >> sharpness improvements.
> >
> >So you are willing to state that no additionally resolved detail would
> >be visible?
>
> I think it is self-evident that he is willing to talk nonsense.
> I would be willing to bet that the vast majority of those who
> pontificate at length about aliasing and moire have zero or near-zero
> experience of using DSLRs that don't have AA filters.
>
> Their arguments are simply theoretical and not based on practical
> considerations.
with aliasing and then complain about the italian flag syndrome. you're
the only one who claims it doesn't happen.
Rich
Feb 8, 2012, 10:17:33 PM2/8/12
to
nospam <nos...@nospam.invalid> wrote in news:080220121149356844%
nos...@nospam.invalid:
If the images are on the up and up, there is definitely extra detail
visible in the HR shots and yes, there is moire in some of them, but the
ones that don't have it are better than the non-modified camera shot. It
should be possible to take care of the moire in post-processing which
means that with the HR camera, you end up with a superior result.
nos...@nospam.invalid:
visible in the HR shots and yes, there is moire in some of them, but the
ones that don't have it are better than the non-modified camera shot. It
should be possible to take care of the moire in post-processing which
means that with the HR camera, you end up with a superior result.
nospam
Feb 8, 2012, 10:46:35 PM2/8/12
to
In article <bYCdnTlunIxQp67S...@giganews.com>, Rich
details.
<no...@nowhere.com> wrote:
> If the images are on the up and up, there is definitely extra detail
> visible in the HR shots and yes, there is moire in some of them, but the
> ones that don't have it are better than the non-modified camera shot. It
> should be possible to take care of the moire in post-processing which
> means that with the HR camera, you end up with a superior result.
you *can't* fix moire in post processing without compromising real
> If the images are on the up and up, there is definitely extra detail
> visible in the HR shots and yes, there is moire in some of them, but the
> ones that don't have it are better than the non-modified camera shot. It
> should be possible to take care of the moire in post-processing which
> means that with the HR camera, you end up with a superior result.
details.
RichA
Feb 9, 2012, 12:49:33 PM2/9/12
to
On Feb 8, 10:46 pm, nospam <nos...@nospam.invalid> wrote:
> In article <bYCdnTlunIxQp67SnZ2dnUVZ_tadn...@giganews.com>, Rich
be superior anyway.
> In article <bYCdnTlunIxQp67SnZ2dnUVZ_tadn...@giganews.com>, Rich
>
> <n...@nowhere.com> wrote:
> > If the images are on the up and up, there is definitely extra detail
> > visible in the HR shots and yes, there is moire in some of them, but the
> > ones that don't have it are better than the non-modified camera shot. It
> > should be possible to take care of the moire in post-processing which
> > means that with the HR camera, you end up with a superior result.
>
> you *can't* fix moire in post processing without compromising real
> details.
Then ignore it in the shots that have it. The shots that don't will
> <n...@nowhere.com> wrote:
> > If the images are on the up and up, there is definitely extra detail
> > visible in the HR shots and yes, there is moire in some of them, but the
> > ones that don't have it are better than the non-modified camera shot. It
> > should be possible to take care of the moire in post-processing which
> > means that with the HR camera, you end up with a superior result.
>
> you *can't* fix moire in post processing without compromising real
> details.
be superior anyway.
Alfred Molon
Feb 9, 2012, 12:57:38 PM2/9/12
to
In article <bYCdnTlunIxQp67S...@giganews.com>, Rich says...
http://www.molon.de/S2/P5.jpg
--
Alfred Molon
------------------------------
Olympus E-series DSLRs and micro 4/3 forum at
http://tech.groups.yahoo.com/group/MyOlympus/
http://myolympus.org/ photo sharing site
> It
> should be possible to take care of the moire in post-processing which
> means that with the HR camera, you end up with a superior result.
Try to fix this moire in postprocessing:
> should be possible to take care of the moire in post-processing which
> means that with the HR camera, you end up with a superior result.
http://www.molon.de/S2/P5.jpg
--
Alfred Molon
------------------------------
Olympus E-series DSLRs and micro 4/3 forum at
http://tech.groups.yahoo.com/group/MyOlympus/
http://myolympus.org/ photo sharing site
Rich
Feb 9, 2012, 8:36:10 PM2/9/12
to
Alfred Molon <alfred...@yahoo.com> wrote in
news:MPG.299e277a1...@news.supernews.com:
> In article <bYCdnTlunIxQp67S...@giganews.com>, Rich says...
>> It
>> should be possible to take care of the moire in post-processing which
>> means that with the HR camera, you end up with a superior result.
>
> Try to fix this moire in postprocessing:
> http://www.molon.de/S2/P5.jpg
I don't have Nikon's new software yet.
news:MPG.299e277a1...@news.supernews.com:
> In article <bYCdnTlunIxQp67S...@giganews.com>, Rich says...
>> It
>> should be possible to take care of the moire in post-processing which
>> means that with the HR camera, you end up with a superior result.
>
> Try to fix this moire in postprocessing:
> http://www.molon.de/S2/P5.jpg
TheRealSteve
Feb 10, 2012, 8:41:33 AM2/10/12
to
On Wed, 08 Feb 2012 10:17:26 -0500, nospam <nos...@nospam.invalid>
wrote:
you're sampling is greater than 1/2 the spatial resolution of your
sensor, given that your lens can also resolve to that level of detail.
It takes a lot more than a solid wall to do that and it doesn't happen
very often in real photos. Of course you can find examples when you're
looking for it. But you have to look through a lot of shots to find
those few examples.
It's simple sampling theory that a lot of poeple just don't seem to
understand.
Steve
nospam
Feb 10, 2012, 8:55:31 AM2/10/12
to
In article <j67aj715fa9d05813...@4ax.com>, TheRealSteve
understand. read what i wrote again. what i said was a simplified
version of what you said.
<st...@example.com> wrote:
> >> Do you honestly want to see that comparison?
> >
> >bring it on. you obviously don't understand what it is you're looking
> >at. if you remove the aa filter, you *will* get artifacts unless there
> >isn't much detail to begin with (e.g., a solid colour wall).
>
> Nope. You will only get artifacts when the spatial frequency of what
> you're sampling is greater than 1/2 the spatial resolution of your
> sensor, given that your lens can also resolve to that level of detail.
> It takes a lot more than a solid wall to do that and it doesn't happen
> very often in real photos. Of course you can find examples when you're
> looking for it. But you have to look through a lot of shots to find
> those few examples.
>
> It's simple sampling theory that a lot of poeple just don't seem to
> understand.
apparently, simple english is what a lot of people just don't seem to
> >> Do you honestly want to see that comparison?
> >
> >bring it on. you obviously don't understand what it is you're looking
> >at. if you remove the aa filter, you *will* get artifacts unless there
> >isn't much detail to begin with (e.g., a solid colour wall).
>
> Nope. You will only get artifacts when the spatial frequency of what
> you're sampling is greater than 1/2 the spatial resolution of your
> sensor, given that your lens can also resolve to that level of detail.
> It takes a lot more than a solid wall to do that and it doesn't happen
> very often in real photos. Of course you can find examples when you're
> looking for it. But you have to look through a lot of shots to find
> those few examples.
>
> It's simple sampling theory that a lot of poeple just don't seem to
> understand.
understand. read what i wrote again. what i said was a simplified
version of what you said.
Bruce
Feb 10, 2012, 9:27:18 AM2/10/12
to
The apparent paranoia about aliasing and moire is misplaced. Because
of that paranoia - about a problem that will only be evident in a very
small percentage of shots - EVERY shot taken by the majority of DSLR
users has fine detail turned to mush by unnecessary AA filters.
nospam
Feb 10, 2012, 9:40:32 AM2/10/12
to
In article <m1aaj7pdq19kb3627...@4ax.com>, Bruce
read english any better than he did.
> The apparent paranoia about aliasing and moire is misplaced. Because
> of that paranoia - about a problem that will only be evident in a very
> small percentage of shots - EVERY shot taken by the majority of DSLR
> users has fine detail turned to mush by unnecessary AA filters.
nonsense. aa filters are a necessary evil and they don't turn fine
detail to mush.
<docne...@gmail.com> wrote:
> >>> Do you honestly want to see that comparison?
> >>
> >>bring it on. you obviously don't understand what it is you're looking
> >>at. if you remove the aa filter, you *will* get artifacts unless there
> >>isn't much detail to begin with (e.g., a solid colour wall).
> >
> >Nope. You will only get artifacts when the spatial frequency of what
> >you're sampling is greater than 1/2 the spatial resolution of your
> >sensor, given that your lens can also resolve to that level of detail.
> >It takes a lot more than a solid wall to do that and it doesn't happen
> >very often in real photos. Of course you can find examples when you're
> >looking for it. But you have to look through a lot of shots to find
> >those few examples.
> >
> >It's simple sampling theory that a lot of poeple just don't seem to
> >understand.
>
> Well said, sir!
hilarious. you clearly have no clue about sampling theory and you can't
> >>> Do you honestly want to see that comparison?
> >>
> >>bring it on. you obviously don't understand what it is you're looking
> >>at. if you remove the aa filter, you *will* get artifacts unless there
> >>isn't much detail to begin with (e.g., a solid colour wall).
> >
> >Nope. You will only get artifacts when the spatial frequency of what
> >you're sampling is greater than 1/2 the spatial resolution of your
> >sensor, given that your lens can also resolve to that level of detail.
> >It takes a lot more than a solid wall to do that and it doesn't happen
> >very often in real photos. Of course you can find examples when you're
> >looking for it. But you have to look through a lot of shots to find
> >those few examples.
> >
> >It's simple sampling theory that a lot of poeple just don't seem to
> >understand.
>
> Well said, sir!
read english any better than he did.
> The apparent paranoia about aliasing and moire is misplaced. Because
> of that paranoia - about a problem that will only be evident in a very
> small percentage of shots - EVERY shot taken by the majority of DSLR
> users has fine detail turned to mush by unnecessary AA filters.
detail to mush.
Floyd L. Davidson
Feb 10, 2012, 7:33:18 PM2/10/12
to
TheRealSteve <st...@example.com> wrote:
>On Wed, 08 Feb 2012 10:17:26 -0500, nospam <nos...@nospam.invalid>
>wrote:
>
>>In article <SbydnbnQneDrS6zS...@giganews.com>, Rich
>><no...@nowhere.com> wrote:
>>
>>> Do you honestly want to see that comparison?
>>
>>bring it on. you obviously don't understand what it is you're looking
>>at. if you remove the aa filter, you *will* get artifacts unless there
>>isn't much detail to begin with (e.g., a solid colour wall).
>
>Nope. You will only get artifacts when the spatial frequency of what
>you're sampling is greater than 1/2 the spatial resolution of your
>sensor, given that your lens can also resolve to that level of detail.
Whoa. Lets stop right there. You have said virtually
>On Wed, 08 Feb 2012 10:17:26 -0500, nospam <nos...@nospam.invalid>
>wrote:
>
>>In article <SbydnbnQneDrS6zS...@giganews.com>, Rich
>><no...@nowhere.com> wrote:
>>
>>> Do you honestly want to see that comparison?
>>
>>bring it on. you obviously don't understand what it is you're looking
>>at. if you remove the aa filter, you *will* get artifacts unless there
>>isn't much detail to begin with (e.g., a solid colour wall).
>
>Nope. You will only get artifacts when the spatial frequency of what
>you're sampling is greater than 1/2 the spatial resolution of your
>sensor, given that your lens can also resolve to that level of detail.
the same thing he said. He isn't wrong. I am not
getting the idea that you have a perspective on what it
means that allows understanding the significance of what
he said (or what you've written either).
>It takes a lot more than a solid wall to do that and it doesn't happen
>very often in real photos. Of course you can find examples when you're
>looking for it. But you have to look through a lot of shots to find
>those few examples.
detail exists in real life objects.
What you have to look hard to find is *not* where
aliasing has happened, but where the aliasing produces
something you can visually identify as aliasing. Hence
if the fine detail is the result of multiple parallel
lines, or even worse if there are two sets of parallel
lines that have different offsets, the result in the
image will be moiré, which can easily be identified.
But if the fine detail is anything else, it is virtually
impossible to identify the resulting detail as the
result of aliasing unless you have a second image that
is exactly the same and does not contain the aliased
detail. Then it is very obvious too.
>It's simple sampling theory that a lot of poeple just don't seem to
>understand.
If you think visible moiré is the only artifact produced
by aliasing, or that other aliasing artifacts are not
detrimental to the quality of an image, then perhaps you
don't yet really understand sampling theory.
TheRealSteve
Feb 11, 2012, 11:03:55 AM2/11/12
to
that's missing from the image that had the aa filter. The detail that
exists in real objects is exactly what the aa filter removes. But you
will get absolutely zero aliasing anywhere in an image where the
detail has not exceeded the nyquist frequency. With today's sensors
that have several times the spatial resolution of sensors of only a
few years ago, there's much less real life detail that exceeds the
sensor's nyquist frequency. Of course it can happen, but much more
rarely.
Couple that with lenses that cannot resolve to level of detail that
the sensor can, the lens itself is acting as an anti-alias filter. No
need to mush it up further with another filter.
>>It's simple sampling theory that a lot of poeple just don't seem to
>>understand.
>
>Do you?
>If you think visible moiré is the only artifact produced
>by aliasing, or that other aliasing artifacts are not
>detrimental to the quality of an image, then perhaps you
>don't yet really understand sampling theory.
moire is most visible with large areas of the same spatial frequency
that is higher than nyquist, such as parallel lines of a brick wall or
fabric texture. Here, the low frequency moire artifact is constant and
creates a "beat" that is constant and visible across a large portion
of the repeating pattern.
In other areas of spatial frequency greater than nyquist that do not
have the same constant spatial frequency, such as a field of grass,
the low frequency artifacts and the resultant moire' are too random to
be easily picked out by your eye as something different than the
randomness of the original field of grass. The moire' patterns
produced are too localized to a small area to be noticed unless you
pixel peep. Over the larger area it's too random to be noticed as a
moire', but it is moire' nonetheless.
The main point is that with today's high resolution sensors coupled
with lens resolution increases that have not kept up with sensor
resolution increases, aliasing is much less of a problem than it used
to be. A body with the aa filter removed is a useful tool in the
hands of a photographer mindful of it's limitations.
Steve
Floyd L. Davidson
Feb 11, 2012, 12:19:50 PM2/11/12
to
frequencies that are higher than the Nyquist Limit (1/2
the sampling frequency) are *folded* down in frequency.
Which is to say that your opening sentence is pure nonsense.
> They show up in the image as something that did
>not exist at all in the original scene. But you
>will get absolutely zero aliasing anywhere in an image where the
>detail has not exceeded the nyquist frequency. With today's sensors
>that have several times the spatial resolution of sensors of only a
>few years ago, there's much less real life detail that exceeds the
>sensor's nyquist frequency. Of course it can happen, but much more
>rarely.
"Much less real life detail"?? That is more nonsense.
>detail has not exceeded the nyquist frequency. With today's sensors
>that have several times the spatial resolution of sensors of only a
>few years ago, there's much less real life detail that exceeds the
>sensor's nyquist frequency. Of course it can happen, but much more
>rarely.
>Couple that with lenses that cannot resolve to level of detail that
>the sensor can, the lens itself is acting as an anti-alias filter. No
>need to mush it up further with another filter.
resolve detail far in excess of even a 36 MP camera like
the D800.
>>>It's simple sampling theory that a lot of poeple just don't seem to
>>>understand.
>>
>>Do you?
>
>Yes, I do.
>>If you think visible moiré is the only artifact produced
>>by aliasing, or that other aliasing artifacts are not
>>detrimental to the quality of an image, then perhaps you
>>don't yet really understand sampling theory.
>
>Yes, moire' is the only artifact produced by undersampling.
immediately after you claim to understand sampling
theory.
>But the
>moire is most visible with large areas of the same spatial frequency
>that is higher than nyquist, such as parallel lines of a brick wall or
>fabric texture. Here, the low frequency moire artifact is constant and
>creates a "beat" that is constant and visible across a large portion
>of the repeating pattern.
>In other areas of spatial frequency greater than nyquist that do not
>have the same constant spatial frequency, such as a field of grass,
>the low frequency artifacts and the resultant moire' are too random to
>be easily picked out by your eye as something different than the
>randomness of the original field of grass. The moire' patterns
>produced are too localized to a small area to be noticed unless you
>pixel peep. Over the larger area it's too random to be noticed as a
>moire', but it is moire' nonetheless.
>The main point is that with today's high resolution sensors coupled
>with lens resolution increases that have not kept up with sensor
>resolution increases, aliasing is much less of a problem than it used
>to be. A body with the aa filter removed is a useful tool in the
>hands of a photographer mindful of it's limitations.
useful tool.
nospam
Feb 11, 2012, 4:56:20 PM2/11/12
to
In article <5b1dj71n7p6hqp8uf...@4ax.com>, TheRealSteve
the sensor because it's too high. if the aa filter wasn't there, that
detail would alias. with the aa filter, there wont be any aliasing.
that's a bit simplistic, but it makes the point. real world aa filters
aren't perfect so there's a bit of a tradeoff as to how strong it needs
to be.
> But you
> will get absolutely zero aliasing anywhere in an image where the
> detail has not exceeded the nyquist frequency.
actually, aliasing starts to become a problem a little below nyquist.
> With today's sensors
> that have several times the spatial resolution of sensors of only a
> few years ago, there's much less real life detail that exceeds the
> sensor's nyquist frequency. Of course it can happen, but much more
> rarely.
several??? more like double. a 24 mp sensor, such as the nikon d3x, has
double the linear resolution than that of a 6mp sensor, such as the
nikon d70.
> Couple that with lenses that cannot resolve to level of detail that
> the sensor can, the lens itself is acting as an anti-alias filter. No
> need to mush it up further with another filter.
maybe *your* lenses don't resolve that well. you obviously need new
lenses, ones which can resolve what the sensor can resolve. and a book
on signal theory.
<st...@example.com> wrote:
> What you think of as "aliased detail" in most cases is real detail
> that's missing from the image that had the aa filter. The detail that
> exists in real objects is exactly what the aa filter removes.
wrong. what the aa filter removes is detail the can't be resolved by
> What you think of as "aliased detail" in most cases is real detail
> that's missing from the image that had the aa filter. The detail that
> exists in real objects is exactly what the aa filter removes.
the sensor because it's too high. if the aa filter wasn't there, that
detail would alias. with the aa filter, there wont be any aliasing.
that's a bit simplistic, but it makes the point. real world aa filters
aren't perfect so there's a bit of a tradeoff as to how strong it needs
to be.
> But you
> will get absolutely zero aliasing anywhere in an image where the
> detail has not exceeded the nyquist frequency.
> With today's sensors
> that have several times the spatial resolution of sensors of only a
> few years ago, there's much less real life detail that exceeds the
> sensor's nyquist frequency. Of course it can happen, but much more
> rarely.
double the linear resolution than that of a 6mp sensor, such as the
nikon d70.
> Couple that with lenses that cannot resolve to level of detail that
> the sensor can, the lens itself is acting as an anti-alias filter. No
> need to mush it up further with another filter.
lenses, ones which can resolve what the sensor can resolve. and a book
on signal theory.
TheRealSteve
Feb 11, 2012, 9:51:25 PM2/11/12
to
On Sat, 11 Feb 2012 08:19:50 -0900, fl...@apaflo.com (Floyd L.
frequency but due to ambiguity in reproduction, the are duplicated.
>Which is to say that your opening sentence is pure nonsense.
image as an artifact when it might not be.
>> They show up in the image as something that did
>>not exist at all in the original scene. But you
>>will get absolutely zero aliasing anywhere in an image where the
>>detail has not exceeded the nyquist frequency. With today's sensors
>>that have several times the spatial resolution of sensors of only a
>>few years ago, there's much less real life detail that exceeds the
>>sensor's nyquist frequency. Of course it can happen, but much more
>>rarely.
>
>"Much less real life detail"?? That is more nonsense.
that we photograph hasn't changed all that much in the past few years
or so and given that sensor spatial resolution has increased by
several factors over the last few years or so (say a decade), then
it's self evident that there's much less real life detail that exceeds
the nyquist frequency of today's sensors than those of a decade ago.
If you're going to argue against an obvious truth then there's not
much point in continuing the discussion
>>>>It's simple sampling theory that a lot of poeple just don't seem to
>>>>understand.
>>>
>>>Do you?
>>
>>Yes, I do.
>
>So far you've said very little that suggests you do.
you think I know little about sampling theory.
>>>If you think visible moiré is the only artifact produced
>>>by aliasing, or that other aliasing artifacts are not
>>>detrimental to the quality of an image, then perhaps you
>>>don't yet really understand sampling theory.
>>
>>Yes, moire' is the only artifact produced by undersampling.
>
>That is an astoundingly ignorant statement to make
>immediately after you claim to understand sampling
>theory.
>>But the
>>moire is most visible with large areas of the same spatial frequency
>>that is higher than nyquist, such as parallel lines of a brick wall or
>>fabric texture. Here, the low frequency moire artifact is constant and
>>creates a "beat" that is constant and visible across a large portion
>>of the repeating pattern.
>
>But that is hardly the only artifact produced.
>>In other areas of spatial frequency greater than nyquist that do not
>>have the same constant spatial frequency, such as a field of grass,
>>the low frequency artifacts and the resultant moire' are too random to
>>be easily picked out by your eye as something different than the
>>randomness of the original field of grass. The moire' patterns
>>produced are too localized to a small area to be noticed unless you
>>pixel peep. Over the larger area it's too random to be noticed as a
>>moire', but it is moire' nonetheless.
>
>No it is not moire', it is simply aliasing distortion.
between, in this case, the original content of an image and alias
artifacts. There's no said limit on how big or small an area of
interference must be in order to be considered moire'. It doesn't have
to be large areas. It's doesn't have to be parallel patterns. It can
be curved, blobby, large or small. In some cases, moire' may even look
like the fringes you get when you over-sharpen. It's only a special
case of interference, or moire', that creates the more familiar
patterns that you might exclusively refer to as a moire' pattern.
>>The main point is that with today's high resolution sensors coupled
>>with lens resolution increases that have not kept up with sensor
>>resolution increases, aliasing is much less of a problem than it used
>>to be. A body with the aa filter removed is a useful tool in the
>>hands of a photographer mindful of it's limitations.
>
>A body with a appropriate AA filter is a much more
>useful tool.
on what the definition of "appropriate" is. Some bodies came with a
much too strong AA filter. The D200 is a notable example.
I'm through debating this with you. Go ahead and have the last word if
you like.
Steve
TheRealSteve
Feb 11, 2012, 10:17:32 PM2/11/12
to
On Sat, 11 Feb 2012 16:56:20 -0500, nospam <nos...@nospam.invalid>
wrote:
>In article <5b1dj71n7p6hqp8uf...@4ax.com>, TheRealSteve
><st...@example.com> wrote:
>
>> What you think of as "aliased detail" in most cases is real detail
>> that's missing from the image that had the aa filter. The detail that
>> exists in real objects is exactly what the aa filter removes.
>
>wrong. what the aa filter removes is detail the can't be resolved by
>the sensor because it's too high. if the aa filter wasn't there, that
>detail would alias. with the aa filter, there wont be any aliasing.
>
>that's a bit simplistic, but it makes the point. real world aa filters
>aren't perfect so there's a bit of a tradeoff as to how strong it needs
>to be.
won't improve images much removing an AA filter if the AA filter is
not too strong. But that's not always the case.
>> But you
>> will get absolutely zero aliasing anywhere in an image where the
>> detail has not exceeded the nyquist frequency.
>
>actually, aliasing starts to become a problem a little below nyquist.
understood about sampling?
>> With today's sensors
>> that have several times the spatial resolution of sensors of only a
>> few years ago, there's much less real life detail that exceeds the
>> sensor's nyquist frequency. Of course it can happen, but much more
>> rarely.
>
>several??? more like double. a 24 mp sensor, such as the nikon d3x, has
>double the linear resolution than that of a 6mp sensor, such as the
>nikon d70.
numbers games. And it's the D800 at 36mp that may be available from
the manufacturer without an AA filter.
>> Couple that with lenses that cannot resolve to level of detail that
>> the sensor can, the lens itself is acting as an anti-alias filter. No
>> need to mush it up further with another filter.
>
>maybe *your* lenses don't resolve that well. you obviously need new
>lenses, ones which can resolve what the sensor can resolve. and a book
>on signal theory.
crack yours open to the part where it explains how aliasing is a
problem with frequencies "a little below nyquist" and tell us what it
says.
Also, check the MTF of your lenses and see if they really will resolve
lines down to the level of a D800 sensor. You may be surprised what
you find.
Steve
nospam
Feb 11, 2012, 10:15:49 PM2/11/12
to
In article <pr7ej7hekp7e6o0ff...@4ax.com>, TheRealSteve
aliasing *is* ?
> >Which is to say that your opening sentence is pure nonsense.
>
> No it's not.
your sentence above definitely is nonsense.
> It's very easy for you to mistake additional detail in an
> image as an artifact when it might not be.
actually, the opposite is what happens. many people mistake alias
artifacts as additional detail, which is why they erroneously assume
removing an aa filter is a good idea.
since you don't seem to understand what aliasing actually is, it's not
too surprising you want to remove the aa filter.
> >> They show up in the image as something that did
> >>not exist at all in the original scene. But you
> >>will get absolutely zero aliasing anywhere in an image where the
> >>detail has not exceeded the nyquist frequency. With today's sensors
> >>that have several times the spatial resolution of sensors of only a
> >>few years ago, there's much less real life detail that exceeds the
> >>sensor's nyquist frequency. Of course it can happen, but much more
> >>rarely.
> >
> >"Much less real life detail"?? That is more nonsense.
>
> Actually, it's not nonsense. It's axiomatic. Given that the real world
> that we photograph hasn't changed all that much in the past few years
> or so and given that sensor spatial resolution has increased by
> several factors over the last few years or so (say a decade), then
> it's self evident that there's much less real life detail that exceeds
> the nyquist frequency of today's sensors than those of a decade ago.
> If you're going to argue against an obvious truth then there's not
> much point in continuing the discussion
in other words, the nyquist frequency of more recent sensors is higher.
you still need an aa filter, just one with a higher cutoff frequency.
<st...@example.com> wrote:
> >>What you think of as "aliased detail" in most cases is real detail
> >>that's missing from the image that had the aa filter. The detail that
> >>exists in real objects is exactly what the aa filter removes.
> >
> >Do you understand what "aliasing" is? Spatial
> >frequencies that are higher than the Nyquist Limit (1/2
> >the sampling frequency) are *folded* down in frequency.
>
> No, they're not *folded* down. They still exist at the original
> frequency but due to ambiguity in reproduction, the are duplicated.
nonsense. yes they are folded down. do you even understand what
> >>What you think of as "aliased detail" in most cases is real detail
> >>that's missing from the image that had the aa filter. The detail that
> >>exists in real objects is exactly what the aa filter removes.
> >
> >Do you understand what "aliasing" is? Spatial
> >frequencies that are higher than the Nyquist Limit (1/2
> >the sampling frequency) are *folded* down in frequency.
>
> No, they're not *folded* down. They still exist at the original
> frequency but due to ambiguity in reproduction, the are duplicated.
aliasing *is* ?
> >Which is to say that your opening sentence is pure nonsense.
>
> No it's not.
> It's very easy for you to mistake additional detail in an
> image as an artifact when it might not be.
artifacts as additional detail, which is why they erroneously assume
removing an aa filter is a good idea.
since you don't seem to understand what aliasing actually is, it's not
too surprising you want to remove the aa filter.
> >> They show up in the image as something that did
> >>not exist at all in the original scene. But you
> >>will get absolutely zero aliasing anywhere in an image where the
> >>detail has not exceeded the nyquist frequency. With today's sensors
> >>that have several times the spatial resolution of sensors of only a
> >>few years ago, there's much less real life detail that exceeds the
> >>sensor's nyquist frequency. Of course it can happen, but much more
> >>rarely.
> >
> >"Much less real life detail"?? That is more nonsense.
>
> Actually, it's not nonsense. It's axiomatic. Given that the real world
> that we photograph hasn't changed all that much in the past few years
> or so and given that sensor spatial resolution has increased by
> several factors over the last few years or so (say a decade), then
> it's self evident that there's much less real life detail that exceeds
> the nyquist frequency of today's sensors than those of a decade ago.
> If you're going to argue against an obvious truth then there's not
> much point in continuing the discussion
you still need an aa filter, just one with a higher cutoff frequency.
nospam
Feb 11, 2012, 11:05:51 PM2/11/12
to
In article <flaej7lepbgfkipvi...@4ax.com>, TheRealSteve
world, there are tradeoffs. most aa filters are well matched.
> >> But you
> >> will get absolutely zero aliasing anywhere in an image where the
> >> detail has not exceeded the nyquist frequency.
> >
> >actually, aliasing starts to become a problem a little below nyquist.
>
> Really? Care to explain that which goes against everything ever
> understood about sampling?
really.
how about you explain why no aliasing at all will occur below nyquist,
which is what you seem to be saying.
> >> With today's sensors
> >> that have several times the spatial resolution of sensors of only a
> >> few years ago, there's much less real life detail that exceeds the
> >> sensor's nyquist frequency. Of course it can happen, but much more
> >> rarely.
> >
> >several??? more like double. a 24 mp sensor, such as the nikon d3x, has
> >double the linear resolution than that of a 6mp sensor, such as the
> >nikon d70.
>
> Now try the comparison with a D1 against a D800.
what for? you said 'sensors of only a few years ago', not those of 13
years ago.
but if you insist, let's compare the d800 with the nikon d1. since the
d1 actually had 10.8 megapixels (but output 2.7 mp), the d800 has just
under twice the linear resolution (1.8x) of the d1 sensor. so much for
'several times'.
> Everyone can play numbers games.
yes, i can see that.
> And it's the D800 at 36mp that may be available from
> the manufacturer without an AA filter.
actually, the d800e has an aa filter and an anti-aa filter.
<http://www.dpreview.com/previews/nikond800/images/d800e-olpf.jpg>
in any event, the d800 at 36 mp is twice the linear resolution of a 9mp
sensor. there weren't any 9mp dslrs, however, there were 10 mp (nikon
d80 & d200 and canon 40d) and 8 mp (canon 30d) dslrs about 5 years or
so ago.
> >> Couple that with lenses that cannot resolve to level of detail that
> >> the sensor can, the lens itself is acting as an anti-alias filter. No
> >> need to mush it up further with another filter.
> >
> >maybe *your* lenses don't resolve that well. you obviously need new
> >lenses, ones which can resolve what the sensor can resolve. and a book
> >on signal theory.
>
> Just having a book on signal theory isn't good enough.
true. you ought to enroll at an engineering school and have someone
explain it to you.
> You may need to
> crack yours open to the part where it explains how aliasing is a
> problem with frequencies "a little below nyquist" and tell us what it
> says.
it says you can get aliasing.
> Also, check the MTF of your lenses and see if they really will resolve
> lines down to the level of a D800 sensor. You may be surprised what
> you find.
no, actually i won't be surprised at all.
<st...@example.com> wrote:
> >> What you think of as "aliased detail" in most cases is real detail
> >> that's missing from the image that had the aa filter. The detail that
> >> exists in real objects is exactly what the aa filter removes.
> >
> >wrong. what the aa filter removes is detail the can't be resolved by
> >the sensor because it's too high. if the aa filter wasn't there, that
> >detail would alias. with the aa filter, there wont be any aliasing.
> >
> >that's a bit simplistic, but it makes the point. real world aa filters
> >aren't perfect so there's a bit of a tradeoff as to how strong it needs
> >to be.
>
> And some are way too strong, which is the point here. Obviously it
> won't improve images much removing an AA filter if the AA filter is
> not too strong. But that's not always the case.
in a perfect world, we could have a perfect aa filter. in the real
> >> What you think of as "aliased detail" in most cases is real detail
> >> that's missing from the image that had the aa filter. The detail that
> >> exists in real objects is exactly what the aa filter removes.
> >
> >wrong. what the aa filter removes is detail the can't be resolved by
> >the sensor because it's too high. if the aa filter wasn't there, that
> >detail would alias. with the aa filter, there wont be any aliasing.
> >
> >that's a bit simplistic, but it makes the point. real world aa filters
> >aren't perfect so there's a bit of a tradeoff as to how strong it needs
> >to be.
>
> And some are way too strong, which is the point here. Obviously it
> won't improve images much removing an AA filter if the AA filter is
> not too strong. But that's not always the case.
world, there are tradeoffs. most aa filters are well matched.
> >> But you
> >> will get absolutely zero aliasing anywhere in an image where the
> >> detail has not exceeded the nyquist frequency.
> >
> >actually, aliasing starts to become a problem a little below nyquist.
>
> Really? Care to explain that which goes against everything ever
> understood about sampling?
how about you explain why no aliasing at all will occur below nyquist,
which is what you seem to be saying.
> >> With today's sensors
> >> that have several times the spatial resolution of sensors of only a
> >> few years ago, there's much less real life detail that exceeds the
> >> sensor's nyquist frequency. Of course it can happen, but much more
> >> rarely.
> >
> >several??? more like double. a 24 mp sensor, such as the nikon d3x, has
> >double the linear resolution than that of a 6mp sensor, such as the
> >nikon d70.
>
> Now try the comparison with a D1 against a D800.
years ago.
but if you insist, let's compare the d800 with the nikon d1. since the
d1 actually had 10.8 megapixels (but output 2.7 mp), the d800 has just
under twice the linear resolution (1.8x) of the d1 sensor. so much for
'several times'.
> Everyone can play numbers games.
> And it's the D800 at 36mp that may be available from
> the manufacturer without an AA filter.
<http://www.dpreview.com/previews/nikond800/images/d800e-olpf.jpg>
in any event, the d800 at 36 mp is twice the linear resolution of a 9mp
sensor. there weren't any 9mp dslrs, however, there were 10 mp (nikon
d80 & d200 and canon 40d) and 8 mp (canon 30d) dslrs about 5 years or
so ago.
> >> Couple that with lenses that cannot resolve to level of detail that
> >> the sensor can, the lens itself is acting as an anti-alias filter. No
> >> need to mush it up further with another filter.
> >
> >maybe *your* lenses don't resolve that well. you obviously need new
> >lenses, ones which can resolve what the sensor can resolve. and a book
> >on signal theory.
>
> Just having a book on signal theory isn't good enough.
explain it to you.
> You may need to
> crack yours open to the part where it explains how aliasing is a
> problem with frequencies "a little below nyquist" and tell us what it
> says.
> Also, check the MTF of your lenses and see if they really will resolve
> lines down to the level of a D800 sensor. You may be surprised what
> you find.
Floyd L. Davidson
Feb 11, 2012, 11:51:50 PM2/11/12
to
TheRealSteve <st...@example.com> wrote:
>On Sat, 11 Feb 2012 08:19:50 -0900, fl...@apaflo.com (Floyd L.
>Davidson) wrote:
>>Do you understand what "aliasing" is? Spatial
>>frequencies that are higher than the Nyquist Limit (1/2
>>the sampling frequency) are *folded* down in frequency.
>
>No, they're not *folded* down. They still exist at the original
>frequency but due to ambiguity in reproduction, the are duplicated.
Ignorant.
>On Sat, 11 Feb 2012 08:19:50 -0900, fl...@apaflo.com (Floyd L.
>Davidson) wrote:
>>Do you understand what "aliasing" is? Spatial
>>frequencies that are higher than the Nyquist Limit (1/2
>>the sampling frequency) are *folded* down in frequency.
>
>No, they're not *folded* down. They still exist at the original
>frequency but due to ambiguity in reproduction, the are duplicated.
>>Which is to say that your opening sentence is pure nonsense.
>
>No it's not. It's very easy for you to mistake additional detail in an
>image as an artifact when it might not be.
by definition.
>>"Much less real life detail"?? That is more nonsense.
>
>Actually, it's not nonsense. It's axiomatic. Given that the real world
>that we photograph hasn't changed all that much in the past few years
>or so and given that sensor spatial resolution has increased by
>several factors over the last few years or so (say a decade), then
>it's self evident that there's much less real life detail that exceeds
>the nyquist frequency of today's sensors than those of a decade ago.
>If you're going to argue against an obvious truth then there's not
>much point in continuing the discussion
you say is ignorant.
Try doing some research and learning a bit about sampling
theory before spouting off again.
>And you're arguing against the indubitable. So it's in my favor that
>you think I know little about sampling theory.
down. They still exist at the original frequency but due
to ambiguity in reproduction, the are duplicated." the
indubitable fact is that you have no understanding of
this topic at all.
Virtually *every* tutorial you'll ever read on the subject
of sampling theory will explain that for you right at the
start. It is essential to understanding almost every other
aspect.
>>>>If you think visible moiré is the only artifact produced
>>>>by aliasing, or that other aliasing artifacts are not
>>>>detrimental to the quality of an image, then perhaps you
>>>>don't yet really understand sampling theory.
>>>
>>>Yes, moire' is the only artifact produced by undersampling.
>>
>>That is an astoundingly ignorant statement to make
>>immediately after you claim to understand sampling
>>theory.
>
>Thank you for continuing your trend.
actual effects of "undersampling" are.
>>>In other areas of spatial frequency greater than nyquist that do not
>>>have the same constant spatial frequency, such as a field of grass,
>>>the low frequency artifacts and the resultant moire' are too random to
>>>be easily picked out by your eye as something different than the
>>>randomness of the original field of grass. The moire' patterns
>>>produced are too localized to a small area to be noticed unless you
>>>pixel peep. Over the larger area it's too random to be noticed as a
>>>moire', but it is moire' nonetheless.
>>
>>No it is not moire', it is simply aliasing distortion.
>
>Apparently you don't know what moire' is. It's simply interference
>between, in this case, the original content of an image and alias
>artifacts. There's no said limit on how big or small an area of
>interference must be in order to be considered moire'. It doesn't have
>to be large areas. It's doesn't have to be parallel patterns. It can
>be curved, blobby, large or small. In some cases, moire' may even look
>like the fringes you get when you over-sharpen. It's only a special
>case of interference, or moire', that creates the more familiar
>patterns that you might exclusively refer to as a moire' pattern.
guarantee there will be interference between original
signal and aliasing distortion. You are just describing
one effect of aliasing distortion, but that is not the
only effect.
Moire' certainly exist on both a large and a small
scale, but it is not the only artifact from aliasing.
>>>The main point is that with today's high resolution sensors coupled
>>>with lens resolution increases that have not kept up with sensor
>>>resolution increases, aliasing is much less of a problem than it used
>>>to be. A body with the aa filter removed is a useful tool in the
>>>hands of a photographer mindful of it's limitations.
>>
>>A body with a appropriate AA filter is a much more
>>useful tool.
>
>Maybe, maybe not. Depends on what you're trying to do.
not, it is absolutely true.
>It also depends
>on what the definition of "appropriate" is. Some bodies came with a
>much too strong AA filter. The D200 is a notable example.
indeed the "appropriate AA filter".
>I'm through debating this with you. Go ahead and have the last word if
>you like.
TheRealSteve
Feb 13, 2012, 9:30:51 AM2/13/12
to
On Sat, 11 Feb 2012 23:05:51 -0500, nospam <nos...@nospam.invalid>
wrote:
nyquist. Of couse out of band aliasing will occur but that's not what
we're talking about. You don't have to be anywhere near nyquist for
that to occur.
>> >> With today's sensors
>> >> that have several times the spatial resolution of sensors of only a
>> >> few years ago, there's much less real life detail that exceeds the
>> >> sensor's nyquist frequency. Of course it can happen, but much more
>> >> rarely.
>> >
>> >several??? more like double. a 24 mp sensor, such as the nikon d3x, has
>> >double the linear resolution than that of a 6mp sensor, such as the
>> >nikon d70.
>>
>> Now try the comparison with a D1 against a D800.
>
>what for? you said 'sensors of only a few years ago', not those of 13
>years ago.
>
>but if you insist, let's compare the d800 with the nikon d1. since the
>d1 actually had 10.8 megapixels (but output 2.7 mp), the d800 has just
>under twice the linear resolution (1.8x) of the d1 sensor. so much for
>'several times'.
sensitivity and SNR. The pixels were grouped together which did
nothing to increase the resolving power, which is what we're talking
about. So the D800 has 3.6x the linear resolution of the D1.
>> You may need to
>> crack yours open to the part where it explains how aliasing is a
>> problem with frequencies "a little below nyquist" and tell us what it
>> says.
>
>it says you can get aliasing.
reputable cite that says you'll get in-band aliasing artifacts (i.e.,
spurious frequencies between 0 and nyquist frequency) if you sample a
little below nyquist.
Steve
David J Taylor
Feb 13, 2012, 10:13:49 AM2/13/12
to
"TheRealSteve" <st...@example.com> wrote in message
news:ej6ij7l7tb7dgn7lr...@4ax.com...
[]
> Wrong. The only reason the D1 had 10.8 MP was for increased
> sensitivity and SNR. The pixels were grouped together which did
> nothing to increase the resolving power, which is what we're talking
> about. So the D800 has 3.6x the linear resolution of the D1.
Nikon D1: 2000 pixels in 23.7 mm - 11.85 um pixel spacing
> sensitivity and SNR. The pixels were grouped together which did
> nothing to increase the resolving power, which is what we're talking
> about. So the D800 has 3.6x the linear resolution of the D1.
Nikon D800: 7360 pixels in 35.9 mm - 4.88 um spacing
2.4 times the linear resolution in pixels per mm. 3.68 times the
resolution in pixels per picture width. Using data from:
http://www.dpreview.com/reviews/nikond1/
http://www.dpreview.com/products/nikon/slrs/nikon_d800
[Interesting comment on the D1 page, dated November 2000: "The D1 was
Nikon's answer to Kodak's domination of the professional SLR's market."
> One cite would suffice. I'm willing to learn. So please find one
> reputable cite that says you'll get in-band aliasing artifacts (i.e.,
> spurious frequencies between 0 and nyquist frequency) if you sample a
> little below nyquist.
>
> Steve
aliasing at just less than Nyquist, but this is using a square-wave light
pattern which has harmonics. Perhaps this explains what is being
reported?
Possible example:
http://a.img-dpreview.com/reviews/Canoneos600d/Samples/Res/IMG_7384-ACR-003.jpg
From: http://www.dpreview.com/reviews/canoneos600d/page11.asp
David
RichA
Feb 13, 2012, 12:52:43 PM2/13/12
to
On Feb 11, 11:51 pm, fl...@apaflo.com (Floyd L. Davidson) wrote:
> >It also depends
> >on what the definition of "appropriate" is. Some bodies came with a
> >much too strong AA filter. The D200 is a notable example.
>
> Too strong for one job, but absolutely correct for a job where it is
> indeed the "appropriate AA filter".
Hey maybe they should offer and AA filter selection set, for different
> >It also depends
> >on what the definition of "appropriate" is. Some bodies came with a
> >much too strong AA filter. The D200 is a notable example.
>
> Too strong for one job, but absolutely correct for a job where it is
> indeed the "appropriate AA filter".
scenes?
Has anyone been inconvenienced because their camera had a "too light"
AA filter?
TheRealSteve
Feb 14, 2012, 8:15:51 AM2/14/12
to
On Mon, 13 Feb 2012 15:13:49 -0000, "David J Taylor"
<david-...@blueyonder.co.uk.invalid> wrote:
>
>Many of the resolution tests showing a step-wedge chart apparently show
>aliasing at just less than Nyquist, but this is using a square-wave light
>pattern which has harmonics. Perhaps this explains what is being
>reported?
>
>Possible example:
>http://a.img-dpreview.com/reviews/Canoneos600d/Samples/Res/IMG_7384-ACR-003.jpg
>From: http://www.dpreview.com/reviews/canoneos600d/page11.asp
>
>David
right at nyquist will have no in-band aliasing. When it's reproduced
it will be reproduced as a square wave, which has the fundamental plus
all of the odd harmonics, each diminishing in amplitude as you go up
in frequency. However, the reconstruction filter will take out those
odd harmonics and reproduce the original sine wave at nyquist. The
original signal *must* have been a sine wave for it not to have any
content above nyquist if the fundamental was right at nyquist. If your
original signal was not a sine wave, then it's frequency content above
nyquist will cause aliasing. This is the case you mentioned above.
While frequencies just below nyquist will have an alias just above
nyquist and frequencies close to 0 will have an alias close to the
sampling frequency, those aliases exist only mathmatically and they
are not reproduced during reconstruction. That's because
reconstruction only reproduces the lowest frequency of all the
possible aliases, of which there are an infinite number.
The problem with aliasing when sampling above nyquist is exactly due
to the fact that reconstruction only reproduces the lowest of the
aliases, which in this case is the wrong one. If all the content is
below or even right at nyquist, there will be no aliases reproduced
during reconstruction.
"nospam" may also be getting confused by what reconstruction filtering
is doing. It has to "smooth the jaggies" produced because you have
steps in the reconstructed signal but the original was probably
smooth. The high frequency content in those steps has nothing to do
with aliasing and they can be removed with a good reconstruction
filter while aliasing cannot be removed by filtering. That's because
the steps' frequency content is well out of band so you can filter it
with a lowpass filter. But the aliasing produced by undersampling is
in band so filtering it won't work because you'll also filter out part
of your original signal.
So in summary: There are no aliases reproduced from digital content if
all of the original sampled signal is at or below the nyquist
frequency. Not even a frequency "a little below nyquist" will cause
aliases to be reproduced. You're going to have to search long and hard
to find a reputable DSP textbook that says otherwise.
Steve
nospam
Feb 14, 2012, 8:38:11 AM2/14/12
to
In article <srlkj75ssnar2dbl6...@4ax.com>, TheRealSteve
<st...@example.com> wrote:
> So in summary: There are no aliases reproduced from digital content if
> all of the original sampled signal is at or below the nyquist
> frequency. Not even a frequency "a little below nyquist" will cause
> aliases to be reproduced. You're going to have to search long and hard
> to find a reputable DSP textbook that says otherwise.
wrong.
> So in summary: There are no aliases reproduced from digital content if
> all of the original sampled signal is at or below the nyquist
> frequency. Not even a frequency "a little below nyquist" will cause
> aliases to be reproduced. You're going to have to search long and hard
> to find a reputable DSP textbook that says otherwise.
David J Taylor
Feb 14, 2012, 8:41:54 AM2/14/12
to
"nospam" <nos...@nospam.invalid> wrote in message
news:140220120838118504%nos...@nospam.invalid...
Perhaps you might provide a citation to support your assertation?
news:140220120838118504%nos...@nospam.invalid...
nospam
Feb 14, 2012, 9:41:31 AM2/14/12
to
In article <jhdob3$2h2$1...@dont-email.me>, David J Taylor
phase. you already provided an example of aliasing below nyquist.
maybe steve can cite a reference for his claims.
<david-...@blueyonder.co.uk.invalid> wrote:
> >> So in summary: There are no aliases reproduced from digital content if
> >> all of the original sampled signal is at or below the nyquist
> >> frequency. Not even a frequency "a little below nyquist" will cause
> >> aliases to be reproduced. You're going to have to search long and hard
> >> to find a reputable DSP textbook that says otherwise.
> >
> > wrong.
>
> Perhaps you might provide a citation to support your assertation?
a signal *at* nyquist could be reproduced as dc, depending on its
> >> So in summary: There are no aliases reproduced from digital content if
> >> all of the original sampled signal is at or below the nyquist
> >> frequency. Not even a frequency "a little below nyquist" will cause
> >> aliases to be reproduced. You're going to have to search long and hard
> >> to find a reputable DSP textbook that says otherwise.
> >
> > wrong.
>
> Perhaps you might provide a citation to support your assertation?
phase. you already provided an example of aliasing below nyquist.
maybe steve can cite a reference for his claims.
David J Taylor
Feb 14, 2012, 10:14:47 AM2/14/12
to
"nospam" <nos...@nospam.invalid> wrote in message
news:140220120941316499%nos...@nospam.invalid...
was just below Nyquist, the harmonics are above Nyquist.
Your cite?
David
nospam
Feb 14, 2012, 10:21:03 AM2/14/12
to
In article <jhdtp8$vhh$1...@dont-email.me>, David J Taylor
<http://www.youtube.com/watch?v=Fy9dJgGCWZI>
<david-...@blueyonder.co.uk.invalid> wrote:
> No, the example I provided had square waves which, even if the fundamental
> was just below Nyquist, the harmonics are above Nyquist.
>
> Your cite?
here's a demo:
> No, the example I provided had square waves which, even if the fundamental
> was just below Nyquist, the harmonics are above Nyquist.
>
> Your cite?
<http://www.youtube.com/watch?v=Fy9dJgGCWZI>
David J Taylor
Feb 14, 2012, 10:26:13 AM2/14/12
to
"nospam" <nos...@nospam.invalid> wrote in message
news:140220121021038821%nos...@nospam.invalid...
Hz, so sampling a 10 Hz wave will obviously give aliasing. Doesn't prove
your point.
nospam
Feb 14, 2012, 10:51:31 AM2/14/12
to
In article <jhduel$433$1...@dont-email.me>, David J Taylor
you can clearly see low frequency artifacts.
<http://i42.tinypic.com/25t802d.jpg>
<david-...@blueyonder.co.uk.invalid> wrote:
> >> No, the example I provided had square waves which, even if the
> >> fundamental
> >> was just below Nyquist, the harmonics are above Nyquist.
> >>
> >> Your cite?
> >
> > here's a demo:
> > <http://www.youtube.com/watch?v=Fy9dJgGCWZI>
>
> If he is sampling at 11 Hz, then the maximum non-aliased frequency is 5.5
> Hz, so sampling a 10 Hz wave will obviously give aliasing. Doesn't prove
> your point.
keep watching. at about :30, he samples at 'slightly above' nyquist and
> >> No, the example I provided had square waves which, even if the
> >> fundamental
> >> was just below Nyquist, the harmonics are above Nyquist.
> >>
> >> Your cite?
> >
> > here's a demo:
> > <http://www.youtube.com/watch?v=Fy9dJgGCWZI>
>
> If he is sampling at 11 Hz, then the maximum non-aliased frequency is 5.5
> Hz, so sampling a 10 Hz wave will obviously give aliasing. Doesn't prove
> your point.
you can clearly see low frequency artifacts.
<http://i42.tinypic.com/25t802d.jpg>
David J Taylor
Feb 14, 2012, 11:46:36 AM2/14/12
to
"nospam" <nos...@nospam.invalid> wrote in message
news:140220121051318480%nos...@nospam.invalid...
comments which have been posted.....
nospam
Feb 14, 2012, 3:30:54 PM2/14/12
to
In article <jhe35c$of$1...@dont-email.me>, David J Taylor
the above screen shot?
<david-...@blueyonder.co.uk.invalid> wrote:
> > keep watching. at about :30, he samples at 'slightly above' nyquist and
> > you can clearly see low frequency artifacts.
> >
> > <http://i42.tinypic.com/25t802d.jpg>
>
> Unfortunately, he omits the reconstruction filter. You need only read the
> comments which have been posted.....
which one explains how you would remove the low frequency component in
> > keep watching. at about :30, he samples at 'slightly above' nyquist and
> > you can clearly see low frequency artifacts.
> >
> > <http://i42.tinypic.com/25t802d.jpg>
>
> Unfortunately, he omits the reconstruction filter. You need only read the
> comments which have been posted.....
the above screen shot?
Bryan
Feb 15, 2012, 2:04:51 AM2/15/12
to
nospam wrote:
> a signal *at* nyquist could be reproduced as dc, depending on its
> phase.
Could it? I see how it could be zero, but a sinusoidal wave sampled at
> a signal *at* nyquist could be reproduced as dc, depending on its
> phase.
twice its frequency should produce +a, -a, +a, -a, ... for some
amplitude 'a'. Or maybe I'm missing something.
> you already provided an example of aliasing below nyquist.
theorem tells us that a periodic, infinitely-repeating signal composed
of sinusoidal waves of frequency less than half the sampling frequency
can be perfectly reproduced from the samples. That assumes the samples
are perfect and there's no limit to the number of samples.
Reproducing the signal from a finite number of measurements is
different. As the frequency of some component of the signal approaches
half the sampling frequency from below, the number of samples required
to produce a reasonable approximation grows without bound, and the
tolerance for imprecision in the samples and their timing approaches
zero. Oversampling is A Good Thing.
Contributors to this thread have raised some fine points on other
limits of applying the mathematical model to our problem, useful as
the theory is. Digital camera sensor-cells are not point samples. They
have area. AA-filters are far from perfect. There's no such thing as a
physical AA-filter that cuts the high spacial frequencies and leaves
the lower ones intact, comparable to what filters for electromagnetic
waves achieve in their domain.
Many AA-filters in excellent digital cameras are made from of two
birefringent layers. They divide the image into four, shifted up,
down, left and right by half a pixel-width or so, then recombined so
the sensor gets each point in the original image at four locations.
The design achieves anti-aliasing, but is scarcely even a crude
approximation of the band-pass filtering that would cut frequencies
above the Nyquist limit. Cheaper AA-filters simply blur.
I myself, an untalented photographer, prefer cameras with AA-filters.
There's a fair point here that sensors have gone to such minute sensor-
cell sizes that the optical systems will only rarely if ever deliver
images that push the Nyquist limit. The same facts support a point on
the other side, in that AA-filters have scaled with the sensors, so
any loss of resolution has shrunk into oblivion. As optics advance
respectably and electronics advance phenomenally, the issue here
becomes *less* significant. The optics will become the limiting
factor, the filter that cuts the unresolvable detail, where they are
not already.
TheRealSteve
Feb 15, 2012, 7:56:40 AM2/15/12
to
On Tue, 14 Feb 2012 15:30:54 -0500, nospam <nos...@nospam.invalid>
wrote:
that point in the video, it's hard to tell what you're seeing in that
example. However, if you take him at his word that he really is
sampling just above nyquist then the low frequency content is not an
alias but instead could be caused by interference with the sampling
artifacts. That could be removed by a reconstruction filter if he had
used one, and then so would the low frequency component.
If you don't use a reconstruction filter then you can't accurately
reproduce the original signal. At the end when he goes to 100Hz
sampling of the 10Hz sinewave, while the interference between Fs and
the signal isn't apparent anymore, he still isn't accurately
reproducing the original signal. He easily could have if he had
included a reconstruction filter.
nospam
Feb 15, 2012, 8:11:30 AM2/15/12
to
In article <u79nj7pa0hjq4oagt...@4ax.com>, TheRealSteve
not be any clearer.
> However, if you take him at his word that he really is
> sampling just above nyquist then the low frequency content is not an
> alias but instead could be caused by interference with the sampling
> artifacts. That could be removed by a reconstruction filter if he had
> used one, and then so would the low frequency component.
it's an alias artifact.
> If you don't use a reconstruction filter then you can't accurately
> reproduce the original signal. At the end when he goes to 100Hz
> sampling of the 10Hz sinewave, while the interference between Fs and
> the signal isn't apparent anymore, he still isn't accurately
> reproducing the original signal. He easily could have if he had
> included a reconstruction filter.
it's substantially better than when he was closer to nyquist.
<st...@example.com> wrote:
> >> > keep watching. at about :30, he samples at 'slightly above' nyquist and
> >> > you can clearly see low frequency artifacts.
> >> >
> >> > <http://i42.tinypic.com/25t802d.jpg>
> >>
> >> Unfortunately, he omits the reconstruction filter. You need only read the
> >> comments which have been posted.....
> >
> >which one explains how you would remove the low frequency component in
> >the above screen shot?
>
> Since he doesn't say anything about specifically what he's doing at
> that point in the video, it's hard to tell what you're seeing in that
> example.
actually, he does say what he's doing and the above screen shot could
> >> > keep watching. at about :30, he samples at 'slightly above' nyquist and
> >> > you can clearly see low frequency artifacts.
> >> >
> >> > <http://i42.tinypic.com/25t802d.jpg>
> >>
> >> Unfortunately, he omits the reconstruction filter. You need only read the
> >> comments which have been posted.....
> >
> >which one explains how you would remove the low frequency component in
> >the above screen shot?
>
> Since he doesn't say anything about specifically what he's doing at
> that point in the video, it's hard to tell what you're seeing in that
> example.
not be any clearer.
> However, if you take him at his word that he really is
> sampling just above nyquist then the low frequency content is not an
> alias but instead could be caused by interference with the sampling
> artifacts. That could be removed by a reconstruction filter if he had
> used one, and then so would the low frequency component.
> If you don't use a reconstruction filter then you can't accurately
> reproduce the original signal. At the end when he goes to 100Hz
> sampling of the 10Hz sinewave, while the interference between Fs and
> the signal isn't apparent anymore, he still isn't accurately
> reproducing the original signal. He easily could have if he had
> included a reconstruction filter.
TheRealSteve
Feb 16, 2012, 9:01:21 AM2/16/12
to
On Wed, 15 Feb 2012 08:11:30 -0500, nospam <nos...@nospam.invalid>
wrote:
>In article <u79nj7pa0hjq4oagt...@4ax.com>, TheRealSteve
><st...@example.com> wrote:
>
>> >> > keep watching. at about :30, he samples at 'slightly above' nyquist and
>> >> > you can clearly see low frequency artifacts.
>> >> >
>> >> > <http://i42.tinypic.com/25t802d.jpg>
>> >>
>> >> Unfortunately, he omits the reconstruction filter. You need only read the
>> >> comments which have been posted.....
>> >
>> >which one explains how you would remove the low frequency component in
>> >the above screen shot?
>>
>> Since he doesn't say anything about specifically what he's doing at
>> that point in the video, it's hard to tell what you're seeing in that
>> example.
>
>actually, he does say what he's doing and the above screen shot could
>not be any clearer.
say specifically what he's doing in the "slightly above nyquist rate",
i.e., the exact frequency he is sampling at ... just like he does for
the other cases of 11Hz, 20Hz and 100Hz.
>> However, if you take him at his word that he really is
>> sampling just above nyquist then the low frequency content is not an
>> alias but instead could be caused by interference with the sampling
>> artifacts. That could be removed by a reconstruction filter if he had
>> used one, and then so would the low frequency component.
>
>it's an alias artifact.
processing theory.
If you want cites, here more than you can handle:
http://www.google.com/search?q=nyquist+theorem
A typical example:
"The sampling theorem states that for a limited bandwidth
(band-limited) signal with maximum frequency fmax, the equally spaced
sampling frequency fs must be greater than twice of the maximum
frequency fmax, i.e.,
fs > 2·fmax
in order to have the signal be uniquely reconstructed without
aliasing.
The frequency 2·fmax is called the Nyquist sampling rate. Half of this
value, fmax, is sometimes called the Nyquist frequency."
So there's your cite that says you can uniquely reconstruct a signal
*without aliasing* if your sample frequency, fs, is anything at all
greater than 2*fmax, even slightly greater. I'm still waiting for one
from you that says you get aliasing when sampling greater than 2*fmax.
>> If you don't use a reconstruction filter then you can't accurately
>> reproduce the original signal. At the end when he goes to 100Hz
>> sampling of the 10Hz sinewave, while the interference between Fs and
>> the signal isn't apparent anymore, he still isn't accurately
>> reproducing the original signal. He easily could have if he had
>> included a reconstruction filter.
>
>it's substantially better than when he was closer to nyquist.
faster without using a reconstruction filter. But that doesn't mean
he's getting aliasing when sampling above nyquist. If you do get
aliasing when just above nyquist, that means you'll get aliasing no
matter how far above nyquist you go, just to a lesser extent. And you
don't. And the reason you don't get aliasing when you sample above
nyquist is explained very well in any signal processing tretise that
covers nyquist-shannon theorem.
Steve
nospam
Feb 16, 2012, 6:25:51 PM2/16/12
to
In article <uf1qj7dgp0hpjuj3s...@4ax.com>, TheRealSteve
<st...@example.com> wrote:
> >> >> > keep watching. at about :30, he samples at 'slightly above' nyquist
> >> >> > and you can clearly see low frequency artifacts.
> >> >> >
> >> >> > <http://i42.tinypic.com/25t802d.jpg>
> >> >>
> >> >> Unfortunately, he omits the reconstruction filter. You need only read
> >> >> the comments which have been posted.....
> >> >
> >> >which one explains how you would remove the low frequency component in
> >> >the above screen shot?
> >>
> >> Since he doesn't say anything about specifically what he's doing at
> >> that point in the video, it's hard to tell what you're seeing in that
> >> example.
> >
> >actually, he does say what he's doing and the above screen shot could
> >not be any clearer.
>
> Great. Then you should be able to point to where in the video he does
> say specifically what he's doing in the "slightly above nyquist rate",
> i.e., the exact frequency he is sampling at ... just like he does for
> the other cases of 11Hz, 20Hz and 100Hz.
i did.
> >> >> > keep watching. at about :30, he samples at 'slightly above' nyquist
> >> >> > and you can clearly see low frequency artifacts.
> >> >> >
> >> >> > <http://i42.tinypic.com/25t802d.jpg>
> >> >>
> >> >> Unfortunately, he omits the reconstruction filter. You need only read
> >> >> the comments which have been posted.....
> >> >
> >> >which one explains how you would remove the low frequency component in
> >> >the above screen shot?
> >>
> >> Since he doesn't say anything about specifically what he's doing at
> >> that point in the video, it's hard to tell what you're seeing in that
> >> example.
> >
> >actually, he does say what he's doing and the above screen shot could
> >not be any clearer.
>
> Great. Then you should be able to point to where in the video he does
> say specifically what he's doing in the "slightly above nyquist rate",
> i.e., the exact frequency he is sampling at ... just like he does for
> the other cases of 11Hz, 20Hz and 100Hz.
Bryan
Feb 17, 2012, 12:28:47 AM2/17/12
to
TheRealSteve wrote:
> If you want cites, here more than you can handle:http://www.google.com/search?q=nyquist+theorem
[...]
> If you want cites, here more than you can handle:http://www.google.com/search?q=nyquist+theorem
> So there's your cite that says you can uniquely reconstruct a signal
> *without aliasing* if your sample frequency, fs, is anything at all
> greater than 2*fmax, even slightly greater. I'm still waiting for one
> from you that says you get aliasing when sampling greater than 2*fmax.
The top hit I get from that Google-search is the Wikipedia article on
> *without aliasing* if your sample frequency, fs, is anything at all
> greater than 2*fmax, even slightly greater. I'm still waiting for one
> from you that says you get aliasing when sampling greater than 2*fmax.
the the theorem, which explains:
"The theorem assumes an idealization of any real-world situation, as
it only applies to signals that are sampled for infinite time; any
time-limited x(t) cannot be perfectly bandlimited. Perfect
reconstruction is mathematically possible for the idealized model but
only an approximation for real-world signals and sampling techniques,
albeit in practice often a very good one."
The assumptions of the theorem are never physically satisfied. As the
signal's highest frequency approaches half the sampling rate, the
number of samples required to well-approximate the signal grows
without bound; the error-tolerance in measurement of the samples
shrinks arbitrarily close to zero.
Nospam was correct that aliasing becomes a problem below the Nyquist
limit. The reason is that, as the signal's highest frequency grows
toward the limit, reconstruction becomes less tolerant of the real-
world's non-conformance to the mathematical model. In practice we
always have a limited number of samples of limited precision, which is
a violation of the Nyquist–Shannon sampling theorem's assumptions;
and, more importantly, a severe practical defect in the edge case of a
signal close to the Nyquist limit. Reconstruction of a significantly
over-sampled signal is much more forgiving.
> Of course it looks substantially better on an o-scope when you sample
> faster without using a reconstruction filter.
reconstruction filter that can recreate the original spectrum. There's
simply not enough information. The problem is at least as bad in
digital image sensors, as we're not actually dealing with periodic
signals. We calculate each pixel from a narrow locality of samples.
Somewhat noisy samples.
TheRealSteve
Feb 17, 2012, 8:06:54 AM2/17/12
to
On Thu, 16 Feb 2012 18:25:51 -0500, nospam <nos...@nospam.invalid>
wrote:
sample rate he's using when he's sampling slightly above nyquist?
The "lost" post was probably the same one where you give cites that
say you get aliasing when sampling slightly greater than 2*fmax.
Steve
nospam
Feb 17, 2012, 2:44:17 PM2/17/12
to
TheRealSteve
Feb 19, 2012, 9:36:20 AM2/19/12
to
On Fri, 17 Feb 2012 14:44:17 -0500, nospam <nos...@nospam.invalid>
wrote:
was when he was 'slightly above' nyquist.
nospam
Feb 19, 2012, 1:07:46 PM2/19/12
to
In article <1422k71pnk83tc60t...@4ax.com>, TheRealSteve
<st...@example.com> wrote:
> Nope, not there. It doesn't say anywhere above what his sample rate
> was when he was 'slightly above' nyquist.
the exact rate doesn't matter, only that it was slightly above.
> Nope, not there. It doesn't say anywhere above what his sample rate
> was when he was 'slightly above' nyquist.
TheRealSteve
Feb 19, 2012, 11:23:18 PM2/19/12
to
On Sun, 19 Feb 2012 13:07:46 -0500, nospam <nos...@nospam.invalid>
wrote:
more of an explanation of what you're seeing in the picture.
Wolfgang Weisselberg
Feb 22, 2012, 8:56:01 PM2/22/12
to
Alfred Molon <alfred...@yahoo.com> wrote:
> In article <bYCdnTlunIxQp67S...@giganews.com>, Rich says...
>> It
>> should be possible to take care of the moire in post-processing which
>> means that with the HR camera, you end up with a superior result.
> Try to fix this moire in postprocessing:
> http://www.molon.de/S2/P5.jpg
Interestingly, noone has taken up the offer. Bruce should at
least have pointed out that your image doesn't exist, the moire
was *certainly* added in post processing and your image absolutely
doesn't happen in the real world anyway.
Rich should have spewed some drivel, too.
-Wolfgang
> In article <bYCdnTlunIxQp67S...@giganews.com>, Rich says...
>> It
>> should be possible to take care of the moire in post-processing which
>> means that with the HR camera, you end up with a superior result.
> Try to fix this moire in postprocessing:
> http://www.molon.de/S2/P5.jpg
Interestingly, noone has taken up the offer. Bruce should at
least have pointed out that your image doesn't exist, the moire
was *certainly* added in post processing and your image absolutely
doesn't happen in the real world anyway.
Rich should have spewed some drivel, too.
-Wolfgang
David J Taylor
Feb 24, 2012, 12:30:48 AM2/24/12
to
"Wolfgang Weisselberg" <ozcv...@sneakemail.com> wrote in message
news:huig19-...@ID-52418.user.berlin.de...
<G>
I had also noticed the silence of those against AA filters.
David
news:huig19-...@ID-52418.user.berlin.de...
I had also noticed the silence of those against AA filters.
David
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