Olympus OM enthusiasts' digital prayers have been answered ...

[Bruce]

As the most eagerly awaited Micro Four Thirds announcement yet draws
closer, 43rumors.com has unretouched images of the new Olympus OM-D
model equipped with a battery grip.

It is a very good looking camera, drawing on featured of the original
Olympus OM 35mm SLRs plus the E Series DSLRs. It is mirrorless but
has a 1.4 million dot EVF in the "pentaprism housing".

The camera is confusingly named the Olympus E-M5 but the front of the
top plate is clearly marked OM-D. It looks like OM-D describes the OM
Digital range, and the model number within that range is E-M5.

Official announcement is on Wednesday February 8.

http://www.43rumors.com/ft5-first-full-size-pictures-of-the-e-m5/

[Rich]

Bruce <docne...@gmail.com> wrote in
news:9vsqi7ddl0vnbrfva...@4ax.com:

> As the most eagerly awaited Micro Four Thirds announcement yet draws
> closer, 43rumors.com has unretouched images of the new Olympus OM-D
> model equipped with a battery grip.
>
> It is a very good looking camera, drawing on featured of the original
> Olympus OM 35mm SLRs plus the E Series DSLRs. It is mirrorless but
> has a 1.4 million dot EVF in the "pentaprism housing".
>

Would be nice if it had the same EVF as the NEX 7 or the V1, but that
aside, it looks really good. OM users have been asking for this for
years and it is nice that Olympus listened. It's size is small, even
with the grip so it won't be a pain to carry. Additionally, yes, it is
not going to be as comfortable to hold as a new, rounded DSLR, but fans
will be willing to live with the sharp angles just to use it.

[Trevor]

What makes this an "OM enthusiasts prayers answered" more so than any
previous E series SLR (other than the OM-D name)?
Does it have an OM lens mount as standard rather than 4/3? Or is it simply
just an E-series evolutionary move away from a reflex prism/mirror.

Trevor.

[Kennedy McEwen]

In article <9vsqi7ddl0vnbrfva...@4ax.com>, Bruce
<docne...@gmail.com> writes

>As the most eagerly awaited Micro Four Thirds announcement yet draws
>closer, 43rumors.com has unretouched images of the new Olympus OM-D
>model equipped with a battery grip.
>
>It is a very good looking camera, drawing on featured of the original
>Olympus OM 35mm SLRs plus the E Series DSLRs.

OM looks outside don't compensate for the tiny 4-turds sensor inside.
--
Kennedy
Yes, Socrates himself is particularly missed;
A lovely little thinker, but a bugger when he's pissed.
Python Philosophers (replace 'nospam' with 'kennedym' when replying)

[Alfred Molon]

In article <tkM1woBj...@kennedym.demon.co.uk>, Kennedy McEwen
says...

> OM looks outside don't compensate for the tiny 4-turds sensor inside.

If you need a camera with a bigger sensor, feel free to buy one. But
especially the lenses will be bigger and heavier.
--

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

[Bruce]

"Trevor" <tre...@home.net> wrote:
>
>What makes this an "OM enthusiasts prayers answered" more so than any
>previous E series SLR (other than the OM-D name)?

The OM-D looks like an Olympus OM, just as the PEN E-P1, 2 and 3 look
like an Olympus Pen F or FT. Yes, it is all about appearances, and
about exploiting the enormous positive sentiment for the OM System.

I am very happy to be exploited and I think many OM enthusiasts will
too. I have no doubt that the OM-D E-M5 will sell very well indeed. I
expect I will buy one at some point, just not immediately.

>Does it have an OM lens mount as standard rather than 4/3? Or is it simply
>just an E-series evolutionary move away from a reflex prism/mirror.

It isn't an E Series body. It doesn't have an E mount. It is a Micro
Four Thirds body. Olympus will be making at least one more E Series
body, but this is not it.

To the sceptics I would ask, where was Olympus before the PEN E-P1 was
introduced? The answer is dead and buried. The E Series was not
selling and sales of compact P&S cameras had peaked.

Panasonic developed Micro Four Thirds without Olympus and went down
the route of making their first camera - the LUMIX G1- with the look
and feel of a modern SLR. Olympus drew on their history and made a
Micro Four Thirds camera that looked like a 1960s PEN.

Although the PEN was an SLR, it didn't look like one. It was an
inspired choice, though, as it helped Olympus gain a greater share of
the Japanese market than Panasonic. The OM-D will provide an even
greater boost to Olympus sales at a time when they really need it.

[Eric Stevens]

On Sun, 05 Feb 2012 19:10:18 +0000, Bruce <docne...@gmail.com>
wrote:

>"Trevor" <tre...@home.net> wrote:
>>
>>What makes this an "OM enthusiasts prayers answered" more so than any
>>previous E series SLR (other than the OM-D name)?
>
>
>The OM-D looks like an Olympus OM, just as the PEN E-P1, 2 and 3 look
>like an Olympus Pen F or FT. Yes, it is all about appearances, and
>about exploiting the enormous positive sentiment for the OM System.
>
>I am very happy to be exploited and I think many OM enthusiasts will
>too. I have no doubt that the OM-D E-M5 will sell very well indeed. I
>expect I will buy one at some point, just not immediately.
>
>
>>Does it have an OM lens mount as standard rather than 4/3? Or is it simply
>>just an E-series evolutionary move away from a reflex prism/mirror.
>
>
>It isn't an E Series body. It doesn't have an E mount. It is a Micro
>Four Thirds body. Olympus will be making at least one more E Series
>body, but this is not it.
>
>To the sceptics I would ask, where was Olympus before the PEN E-P1 was
>introduced? The answer is dead and buried. The E Series was not
>selling and sales of compact P&S cameras had peaked.
>
>Panasonic developed Micro Four Thirds without Olympus and went down
>the route of making their first camera - the LUMIX G1- with the look
>and feel of a modern SLR. Olympus drew on their history and made a
>Micro Four Thirds camera that looked like a 1960s PEN.
>
>Although the PEN was an SLR, it didn't look like one.

Surely that's wrong. The PEN was never an SLR?

>It was an
>inspired choice, though, as it helped Olympus gain a greater share of
>the Japanese market than Panasonic. The OM-D will provide an even
>greater boost to Olympus sales at a time when they really need it.

Regards,

Eric Stevens

[David J. Littleboy]

"Eric Stevens" <eric.s...@sum.co.nz> wrote:
> On Sun, 05 Feb 2012 19:10:18 +0000, Bruce <docne...@gmail.com>

>>Panasonic developed Micro Four Thirds without Olympus and went down
>>the route of making their first camera - the LUMIX G1- with the look
>>and feel of a modern SLR. Olympus drew on their history and made a
>>Micro Four Thirds camera that looked like a 1960s PEN.
>>
>>Although the PEN was an SLR, it didn't look like one.
>
> Surely that's wrong. The PEN was never an SLR?

The 1960s PEN F and PEN FT certainly were.

http://en.wikipedia.org/wiki/Olympus_Pen_F

--
David J. Littleboy
Tokyo, Japan

[Eric Stevens]

You can knock me down with a feather!

A friend of mine had an 'F' many years ago and I never knew it was a
reflex.

Regards,

Eric Stevens

[RichA]

Non-crappy OVF, no crappy plastic body, less bloated than the E-3/5
pro bodies, fans have always said they wanted an OM-type digital.
Plus, according to the latest rumours, Olympus is going to release
another reflex camera anyway.

[Trevor]

"Bruce" <docne...@gmail.com> wrote in message
news:ctjti71t4far5j0v8...@4ax.com...

>>What makes this an "OM enthusiasts prayers answered" more so than any
>>previous E series SLR (other than the OM-D name)?
>
> The OM-D looks like an Olympus OM, just as the PEN E-P1, 2 and 3 look
> like an Olympus Pen F or FT. Yes, it is all about appearances, and
> about exploiting the enormous positive sentiment for the OM System.
>
> I am very happy to be exploited and I think many OM enthusiasts will
> too. I have no doubt that the OM-D E-M5 will sell very well indeed. I
> expect I will buy one at some point, just not immediately.

As a long time OM enthusiast I can say it will take more than a retro look
for me to buy one. My Canon DSLR's take my OM lenses with adapters just the
same as the E-series or OM-D will.
Now if it had an OM mount with aperture automation, it might "answer some of
my prayers", but it doesn't.

Trevor.

[mscir]

<snip>

> It isn't an E Series body. It doesn't have an E mount. It is a Micro
> Four Thirds body. Olympus will be making at least one more E Series
> body, but this is not it.

I own and E-620 and I'm still learning about Olympus products. What is
the E mount you referred to?


--- Posted via news://freenews.netfront.net/ - Complaints to ne...@netfront.net ---

[Bruce]

Then your prayers are slightly different, Trevor. ;-)

Many, if not most OM Zuiko lenses present significant problems when
used on a (Micro) Four Thirds digital sensor. The sensor design
strongly prefers telecentric lenses, where most of the light rays are
approximately perpendicular to the sensor when they hit.

But the OM Zuiko lenses were designed primarily for compactness and
light weight - small and light was the USP of the OM System - and this
coincidentally tended to produce lenses that were far from
telecentric. That didn't matter with film, which can record light
rays from all angles; all that mattered was where they hit the film,
not at what angle. But with a digital sensor, light rays striking at
oblique angles generate a much lower response from the receptors.

The result is that many OM lenses are poor performers on digital
sensors, particularly on the small (Micro) Four Thirds sensor. They
suffer particularly from vignetting and their overall performance is
degraded compared to their performance on film.

Olympus helpfully released a list of OM lenses with indications as to
which would performed well, or less well, with suggested limitations
on some in terms of lens apertures. I was so put off by the
complexity of this list, and the dire warnings it contained, that I
never even tried an OM Zuiko lens on my E-1 bodies. There was no need
because I no longer owned any OM gear and the Zuiko Digital lenses
were in any case superb.

So the OM-D E-M5 is not intended as a digital body for use with OM
lenses. It is more about retro styling that taps into the positive
sentiment for the OM system that is still around. People will buy it
because it looks like an OM SLR, not because it accepts OM lenses.

I accept that some people won't like it. But that's true of every
other product on the market.

[Bruce]

mscir <ms...@yahoo.com> wrote:
><snip>
>> It isn't an E Series body. It doesn't have an E mount. It is a Micro
>> Four Thirds body. Olympus will be making at least one more E Series
>> body, but this is not it.
>
>I own and E-620 and I'm still learning about Olympus products. What is
>the E mount you referred to?

It's the mount that Olympus Four Thirds DSLRs use; it is the mount on
your camera and lenses.

Micro Four Thirds cameras use a different mount. However, it is based
on the technology of the E mount and there are adapters available
which allow the use of E mount lenses on Micro Four Thirds cameras.

[RichA]

On Feb 6, 6:14 am, Bruce <docnews2...@gmail.com> wrote:
> "Trevor" <tre...@home.net> wrote:
> >"Bruce" <docnews2...@gmail.com> wrote in message

> >news:ctjti71t4far5j0v8...@4ax.com...
> >>>What makes this an "OM enthusiasts prayers answered" more so than any
> >>>previous E series SLR (other than the OM-D name)?
>
> >> The OM-D looks like an Olympus OM, just as the PEN E-P1, 2 and 3 look
> >> like an Olympus Pen F or FT.  Yes, it is all about appearances, and
> >> about exploiting the enormous positive sentiment for the OM System.
>
> >> I am very happy to be exploited and I think many OM enthusiasts will
> >> too.  I have no doubt that the OM-D E-M5 will sell very well indeed. I
> >> expect I will buy one at some point, just not immediately.
>
> >As a long time OM enthusiast I can say it will take more than a retro look
> >for me to buy one. My Canon DSLR's take my OM lenses with adapters just the
> >same as the E-series or OM-D will.
> >Now if it had an OM mount with aperture automation, it might "answer some of
> >my prayers", but it doesn't.
>
> Then your prayers are slightly different, Trevor.  ;-)
>
> Many, if not most OM Zuiko lenses present significant problems when
> used on a (Micro) Four Thirds digital sensor.  The sensor design
> strongly prefers telecentric lenses, where most of the light rays are
> approximately perpendicular to the sensor when they hit.
>
> But the OM Zuiko lenses were designed primarily for compactness and
> light weight - small and light was the USP of the OM System - and this
> coincidentally tended to produce lenses that were far from
> telecentric.

True, but people should experiment. However, it is true that a good
micro m4/3rds lens (even a zoom) will produce better images than some
of the OM glass across the field. I can see vignetting with an 85mm
f2.0 OM lens, even at f8.0 on a micro 4/3rds sensor. This probably
runs counter-intuitive to idea held by some who think that because the
lens covers a 35mm film plane it won't vignette on a small sensor.

[Mort]

Eric Stevens wrote:
> Surely that's wrong. The PEN was never an SLR?
>

Hi,

There certainly was a PEN SLR, as I owned one. It was half frame camera.

Mort Linder

[Mort]

Hi,

I still have about a dozen OM lenses for my two OM-4T bodies. It
certainly would be nice to have a new Olympus digital body with the OM
lens mount and auto diaphragm, and I would not mind manual focus. I
suppose that it is just daydreaming.

Mort Linder

[Mike]

So larger format than mini 4/3


--
Mike

[Trevor]

"Bruce" <docne...@gmail.com> wrote in message

news:ghcvi7h4m1t848u81...@4ax.com...

> Many, if not most OM Zuiko lenses present significant problems when
> used on a (Micro) Four Thirds digital sensor. The sensor design
> strongly prefers telecentric lenses, where most of the light rays are
> approximately perpendicular to the sensor when they hit.

Right, so just who's "prayers" are being answered simply by a retro "OM"
look I wonder? The "look" was hardly what attracted most people to the OM
system, it was the size weight and performance for me.

> The result is that many OM lenses are poor performers on digital
> sensors, particularly on the small (Micro) Four Thirds sensor. They
> suffer particularly from vignetting and their overall performance is
> degraded compared to their performance on film.

Haven't used one on 4/3, but I'm puzzled how they suffer from any
significant vignetting when your only using the middle half of the lens
circle?

> Olympus helpfully released a list of OM lenses with indications as to
> which would performed well, or less well, with suggested limitations
> on some in terms of lens apertures. I was so put off by the
> complexity of this list, and the dire warnings it contained,

Do you have a link for that list? Sounds interesting.

> that I
> never even tried an OM Zuiko lens on my E-1 bodies. There was no need
> because I no longer owned any OM gear and the Zuiko Digital lenses
> were in any case superb.

True, I would only use an OM lens because I already had it and did not want
to buy another lens of that type. Which also rules out buying another camera
body just to use the old lenses I guess! So looks like my "OM enthisiasts
prayers" are never going to be answered :-(

> So the OM-D E-M5 is not intended as a digital body for use with OM
> lenses. It is more about retro styling that taps into the positive
> sentiment for the OM system that is still around. People will buy it
> because it looks like an OM SLR, not because it accepts OM lenses.

Right, hardly anybody "praying" for that AFAIK. Which is NOT to say it won't
be a good camera for some, or that nobody will buy it of course.

Trevor.

[Bruce]

"Trevor" <tre...@home.net> wrote:

>"Bruce" <docne...@gmail.com> wrote:
>> The result is that many OM lenses are poor performers on digital
>> sensors, particularly on the small (Micro) Four Thirds sensor. They
>> suffer particularly from vignetting and their overall performance is
>> degraded compared to their performance on film.
>
>Haven't used one on 4/3, but I'm puzzled how they suffer from any
>significant vignetting when your only using the middle half of the lens
>circle?

I explained it in my previous post. You replied to that post but
snipped the relevant paragraph. ;-)

> > Olympus helpfully released a list of OM lenses with indications as to
>> which would performed well, or less well, with suggested limitations
>> on some in terms of lens apertures. I was so put off by the
>> complexity of this list, and the dire warnings it contained,
>
>Do you have a link for that list? Sounds interesting.

It was on the Olympus Four Thirds web site.

[Bruce]

Mort <mo...@cloud9.net> wrote:
>
>I still have about a dozen OM lenses for my two OM-4T bodies. It
>certainly would be nice to have a new Olympus digital body with the OM
>lens mount and auto diaphragm, and I would not mind manual focus. I
>suppose that it is just daydreaming.

Unfortunately yes, that is just daydreaming. Olympus rejected the
idea of a digital OM because of the incompatibility of many OM lenses
with digital sensors, which I explained in the post you replied to.

[Bruce]

The Olympus PEN F, FT and FV were half frame 35mm SLRs made from 1963
to 1970, still being sold as late as 1974.

The current PEN E-P3 (and previous E-P1 and E-P2) mirrorless digital
cameras are styled to resemble the PEN F, FT and FV.

However, the first PEN was made in 1959. It was a viewfinder camera.
A range of non-reflex PENs were made from 1959 into the 1980s.

http://en.wikipedia.org/wiki/Olympus_Pen

[Trevor]

"Bruce" <docne...@gmail.com> wrote in message

news:c6m1j75vu3khmc58o...@4ax.com...

>>Haven't used one on 4/3, but I'm puzzled how they suffer from any
>>significant vignetting when your only using the middle half of the lens
>>circle?
>
>
> I explained it in my previous post. You replied to that post but
> snipped the relevant paragraph. ;-)

No, you explained why it would happen if you were using the full lens image
circle, but since your not, I can't see how it's a big problem? Sure there
might be a slightly measurable loss, but a visable vignette, really? Not
saying your wrong, but I'd love to know the TRUE extent.

Trevor.

[Bruce]

"Trevor" <tre...@home.net> wrote:
>"Bruce" <docne...@gmail.com> wrote in message
>news:c6m1j75vu3khmc58o...@4ax.com...
>>>Haven't used one on 4/3, but I'm puzzled how they suffer from any
>>>significant vignetting when your only using the middle half of the lens
>>>circle?
>>
>>
>> I explained it in my previous post. You replied to that post but
>> snipped the relevant paragraph. ;-)
>
>No, you explained why it would happen if you were using the full lens image
>circle, but since your not, I can't see how it's a big problem?

You obviously didn't read what I wrote. Your loss. ;-)

[Trevor]

"Bruce" <docne...@gmail.com> wrote in message

news:gam1j75uf35h6uuht...@4ax.com...

Well it's all relative. I note they don't recommend the 75-150 below 100mm
and 5.6, yet it works well enough on a Canon DSLR, on par with the kit zooms
at least, which are only f5.6 at that range anyway. And most of the other OM
lenses I have seem to be reasonably OK on their list.

Have you actually tried any OM lenses on a E-series camera yourself? I think
Olympus is just advising caution. And of course they'd prefer to sell more
new lenses :-)
But as I said, buying a fairly expensive DSLR body just to use some old
sub-optimal lenses is probably not such a great idea anyway. And simply
using a retro look as a marketing feature will appeal to some, but there are
more important things I look for in a camera.

Trevor.

[Trevor]

"Bruce" <docne...@gmail.com> wrote in message

news:fc22j71qbjfevof8p...@4ax.com...

>>>>Haven't used one on 4/3, but I'm puzzled how they suffer from any
>>>>significant vignetting when your only using the middle half of the lens
>>>>circle?
>>>
>>>
>>> I explained it in my previous post. You replied to that post but
>>> snipped the relevant paragraph. ;-)
>>
>>No, you explained why it would happen if you were using the full lens
>>image
>>circle, but since your not, I can't see how it's a big problem?
>
>
> You obviously didn't read what I wrote. Your loss. ;-)

Nope I read it, and it doesn't match my experience, so I queried what YOUR
experience was? (rather than theory)
Maybe it's only a major problem with Olympus 4/3 sensors perhaps, but as I
said, it's all relative.

Trevor.

[Bruce]

Not only don't you understand what I wrote, but you seem wilfully
determined not to understand. As I said, it's your loss, but you
might like to consider the meaning of the terms "telecentric" and
"oblique".

As for experience, I have bench tested many lenses in addition to real
world testing, and advised one of Europe's largest camera importers on
the issue of compatibility of lenses that were designed for film with
digital sensors. That involved testing every single lens in their
current range, plus some older lenses, on their early digital SLRs.

It was more of a problem with Olympus (Kodak) sensors than with other
brands because the Kodak sensors were specifically designed to be used
with near-telecentric lenses, and performed particularly badly with
lenses that were far from telecentric. The Zuiko Digital lenses are
remarkably telecentric and produced outstanding results on Kodak
sensors.

Alas, the OM Zuiko range included many lenses that were far from
telecentric; Olympus's quest for small size and lightness meant that
light rays from many Zuiko lenses hit the film/sensor at seriously
oblique angles. Hence the need for Olympus to list (1) the lenses
that would work well on digital, (2) the lenses that would work less
well (perhaps with limitations on aperture) and (3) those that
wouldn't work at all well.

If there wasn't a problem, as you so confidently assert, why on earth
would Olympus have gone to such lengths?

Your Head In The Sand Club membership card is in the mail. ;-)

[Kennedy McEwen]

In article <kp62j7h2k806akg8h...@4ax.com>, Bruce
<docne...@gmail.com> writes

>
>If there wasn't a problem, as you so confidently assert, why on earth
>would Olympus have gone to such lengths?
>

To justify making small 4-turds sensors in the first place!
That's when they came out with the "telecentric is best for digital"
myth in the first place and it was shortly proven to be wrong by
measurement. The light fall-off due to non-telecentricity is *LESS* on
Olympus (and Canon FF sensors for that matter) than it was on film!

OM lenses work just as well on digital as they did on film, which
doesn't mean telecentric lenses can't work better, but the argument was
false to begin with and was merely an attempt by Olympus to justify
their investment in cheap chips.

Try the counter argument: if there was a problem, why are the 4-turds
consortium the only folk that have it? Whilst Leica do take steps to
reduce the issue on their sensor, neither Canon, Nikon nor Sony do.

[Kennedy McEwen]

In article <gam1j75uf35h6uuht...@4ax.com>, Bruce
<docne...@gmail.com> writes

Which is just nonsense - I have several OM lenses that work just as
well, perhaps even better, on my Canon FF sensors as they did on film in
an OM body.

[Kennedy McEwen]

In article <MPG.2998e821a...@news.supernews.com>, Alfred Molon
<alfred...@yahoo.com> writes

>In article <tkM1woBj...@kennedym.demon.co.uk>, Kennedy McEwen
>says...
>> OM looks outside don't compensate for the tiny 4-turds sensor inside.
>
>If you need a camera with a bigger sensor, feel free to buy one. But
>especially the lenses will be bigger and heavier.

I have one, and the original OM lenses work very well on it thank you
very much. In fact, I posted some measured results from them on this
forum about 5 years ago - try Google!

[Kennedy McEwen]

In article <ghcvi7h4m1t848u81...@4ax.com>, Bruce
<docne...@gmail.com> writes

>
>Many, if not most OM Zuiko lenses present significant problems when
>used on a (Micro) Four Thirds digital sensor. The sensor design
>strongly prefers telecentric lenses, where most of the light rays are
>approximately perpendicular to the sensor when they hit.
>

That statement is simple repetition of Olympus's original false
justification for making the 4-turds sensor smaller than FF in the first
place, and that was disproved when FF sensors were demonstrated to work
perfectly well with OM lenses. There is NOTHING in the Olympus sensor
design which "strongly prefers telecentric lenses" and several 4-turds
lenses are just as non-telecentric as their equivalent OM lenses were.

[Pete A]

On 2012-02-07 13:12:37 +0000, Kennedy McEwen said:

> In article <kp62j7h2k806akg8h...@4ax.com>, Bruce
> <docne...@gmail.com> writes
>>
>> If there wasn't a problem, as you so confidently assert, why on earth
>> would Olympus have gone to such lengths?
>>
> To justify making small 4-turds sensors in the first place!
> That's when they came out with the "telecentric is best for digital"
> myth in the first place and it was shortly proven to be wrong by
> measurement. The light fall-off due to non-telecentricity is *LESS* on
> Olympus (and Canon FF sensors for that matter) than it was on film!

Illumination falloff for a non-telecentric lens is approximately a
cosine to the fourth power. The only way a digital sensor can suffer
_less_ falloff than film is by altering the angle of the non-central
micro-lenses. In all other cases, a digitital sensor will suffer more
light falloff than film.

[Trevor]

"Bruce" <docne...@gmail.com> wrote in message

news:kp62j7h2k806akg8h...@4ax.com...

> Not only don't you understand what I wrote, but you seem wilfully
> determined not to understand.

DITTO!

> If there wasn't a problem, as you so confidently assert,

I only suggested it didn't match my experience and you have now explained
why. Thank you!

> Your Head In The Sand Club membership card is in the mail. ;-)

Your unnecessarily antagonistic club membership card is in the mail, no
wait, not worth the postage. :-)

Trevor.

[Kennedy McEwen]

In article <2012020714103581999-pete3attkins@nospamntlworldcom>, Pete A
<pete3....@nospam.ntlworld.com> writes

>On 2012-02-07 13:12:37 +0000, Kennedy McEwen said:
>
>> In article <kp62j7h2k806akg8h...@4ax.com>, Bruce
>><docne...@gmail.com> writes
>>> If there wasn't a problem, as you so confidently assert, why on
>>>earth
>>> would Olympus have gone to such lengths?
>>>
>> To justify making small 4-turds sensors in the first place!
>> That's when they came out with the "telecentric is best for digital"
>>myth in the first place and it was shortly proven to be wrong by
>>measurement. The light fall-off due to non-telecentricity is *LESS*
>>on Olympus (and Canon FF sensors for that matter) than it was on film!
>
>Illumination falloff for a non-telecentric lens is approximately a
>cosine to the fourth power. The only way a digital sensor can suffer
>_less_ falloff than film is by altering the angle of the non-central
>micro-lenses.

Wrong.

3D microlens v's 2D flat film surface. A tennis ball has the same cross
section no matter what angle you view it from, while a flat sheet of
film has a cross section that is cos^2. Any 3D view of the microlens
means less than cos^4 fall-off. Also, if the "image" from the
micro-lens is smaller than the sensitive area of the pixel, the
illumination fall-off on a digital sensor will *always* be less than
film - by 2 of those four cosines!

Try measuring it, its not that difficult but too many folk would prefer
to regurgitate the dogma than find out the truth for themselves!
Alternatively, google my measurements from 5 or 6 years ago where this
was discussed to death - the Olympus dogma death!

The Olympus "telecentric" argument was just an excuse for selling tiny
cheap chips. Nothing wrong with that - there is a huge market for
cheaper cameras - but they lost all credibility by trying to justify an
economic argument with fake science.

[Bruce]

"Trevor" <tre...@home.net> wrote:

>"Bruce" <docne...@gmail.com> wrote:
>> Not only don't you understand what I wrote, but you seem wilfully
>> determined not to understand.
>

>> If there wasn't a problem, as you so confidently assert,
>
>I only suggested it didn't match my experience and you have now explained
>why. Thank you!

You're welcome. But I didn't add anything that wasn't already in the
post you decided not to read. ;-)

[Rol_Lei Nut]

On 2/7/2012 14:12, Kennedy McEwen wrote:

> OM lenses work just as well on digital as they did on film, which
> doesn't mean telecentric lenses can't work better, but the argument was
> false to begin with and was merely an attempt by Olympus to justify
> their investment in cheap chips.

I have a Panasonic M43 and use *lots* of made for film lenses on it
(M42, Zeiss, Leica both M & R, M39 & others).

Some lenses, especially fast one, often don't work well at their faster
apertures (by "not well" I mean visibly less well than on a film camera).
It's hard to predict which will do well and which won't: a 85mm 1.4 only
gets good at 2.8 whereas a 35mm 1.4 is very good wide open. Also,
rangefinder lenses don't necessarily do worse than SLR lenses, just as
telephoto lenses (like the 85mm I mentioned) don't always do well.

But my definite conclusion is that, many lenses (perhaps as much as 50%)
*don't* work as well on a M43 sensor as they do on film. So there is
something going on... ;-)

[Pete A]

On 2012-02-08 00:57:00 +0000, Kennedy McEwen said:

> In article <2012020714103581999-pete3attkins@nospamntlworldcom>, Pete A
> <pete3....@nospam.ntlworld.com> writes
>> On 2012-02-07 13:12:37 +0000, Kennedy McEwen said:
>>
>>> In article <kp62j7h2k806akg8h...@4ax.com>, Bruce
>>> <docne...@gmail.com> writes
>>>> If there wasn't a problem, as you so confidently assert, why on earth
>>>> would Olympus have gone to such lengths?
>>>>
>>> To justify making small 4-turds sensors in the first place!
>>> That's when they came out with the "telecentric is best for digital"
>>> myth in the first place and it was shortly proven to be wrong by
>>> measurement. The light fall-off due to non-telecentricity is *LESS* on
>>> Olympus (and Canon FF sensors for that matter) than it was on film!
>>
>> Illumination falloff for a non-telecentric lens is approximately a
>> cosine to the fourth power. The only way a digital sensor can suffer
>> _less_ falloff than film is by altering the angle of the non-central
>> micro-lenses.
>
> Wrong.
>
> 3D microlens v's 2D flat film surface. A tennis ball has the same
> cross section no matter what angle you view it from, while a flat sheet
> of film has a cross section that is cos^2. Any 3D view of the
> microlens means less than cos^4 fall-off.

Half a tennis ball clearly reduces its cross section as the angle moves
away from perpendicular.

> Also, if the "image" from the micro-lens is smaller than the sensitive
> area of the pixel, the illumination fall-off on a digital sensor will
> *always* be less than film - by 2 of those four cosines!

That is simply trading pixel sensitivity for pixel vignetting. There's
a nice illustration on page 44 of the Leica M-Sytem Catalog (page 23 of
the PDF):

<http://us.leica-camera.com/assets/file/download.php?filename=file_5691.pdf>

> Try measuring it, its not that difficult but too many folk would prefer
> to regurgitate the dogma than find out the truth for themselves!
> Alternatively, google my measurements from 5 or 6 years ago where this
> was discussed to death - the Olympus dogma death!

Most (D)SLRs work adequately with most lenses because the lens mount to
sensor/film distance is relatively large. This requires wide-angle
lenses to be retrofocus designs, which is also, in effect, performing
the function of your tennis ball analogy. Indeed, a retrofocus
wide-angle shows less light falloff with both film and digital.

As an example, cos^4 of 33 degrees is 0.49, which is 1 f-stop of light
falloff. Many lenses suffer more than 1-stop of corner vignetting (when
wide-open) and this is generally considered to be acceptable. Reducing
the angle to, say, 15 degrees reduces the falloff to 13%, which is a
negligible 0.2 f-stop.

> The Olympus "telecentric" argument was just an excuse for selling tiny
> cheap chips. Nothing wrong with that - there is a huge market for
> cheaper cameras - but they lost all credibility by trying to justify an
> economic argument with fake science.

What they forgot to mention was that telecentric lenses are much more
affected by dust on the rear element :-)

[nospam]

In article <ghcvi7h4m1t848u81...@4ax.com>, Bruce

<docne...@gmail.com> wrote:

> Many, if not most OM Zuiko lenses present significant problems when
> used on a (Micro) Four Thirds digital sensor. The sensor design
> strongly prefers telecentric lenses, where most of the light rays are
> approximately perpendicular to the sensor when they hit.

the issue is nowhere near as bad as olympus would like you to believe,
and many lenses already were telecentric anyway.

> But the OM Zuiko lenses were designed primarily for compactness and
> light weight - small and light was the USP of the OM System - and this
> coincidentally tended to produce lenses that were far from
> telecentric. That didn't matter with film, which can record light
> rays from all angles; all that mattered was where they hit the film,
> not at what angle. But with a digital sensor, light rays striking at
> oblique angles generate a much lower response from the receptors.

maybe if there aren't microlenses, but just about every sensor in the
last decade has microlenses so it's a non-issue.

> The result is that many OM lenses are poor performers on digital
> sensors, particularly on the small (Micro) Four Thirds sensor. They
> suffer particularly from vignetting and their overall performance is
> degraded compared to their performance on film.

old lenses are actually quite good, and the ones that aren't good are
because they were not very good to begin with, not because of digital.
some of them were telecentric, which blows the entire theory to bits.

isn't it strange how old nikon and pentax lenses work just fine and
produce terrific results, so much so that some of those old lenses are
actively sought after and prices are now much higher than they used to
be. even canon users like old nikon lenses (they can't use old canon
lenses due to the change in the mount).

that means that either the old olympus lenses were junk or that this
'theory' is a total crock. anyone who used old olympus lenses knows
they weren't junk, which leaves only one other possibility.

> Olympus helpfully released a list of OM lenses with indications as to
> which would performed well, or less well, with suggested limitations
> on some in terms of lens apertures. I was so put off by the
> complexity of this list, and the dire warnings it contained, that I
> never even tried an OM Zuiko lens on my E-1 bodies. There was no need
> because I no longer owned any OM gear and the Zuiko Digital lenses
> were in any case superb.

olympus released a lot of bullshit about digital lenses that sounds
good on the surface but is nothing but bullshit.

[nospam]

In article <eg05xmJc...@kennedym.demon.co.uk>, Kennedy McEwen

<r...@nospam.demon.co.uk> wrote:

> The Olympus "telecentric" argument was just an excuse for selling tiny
> cheap chips. Nothing wrong with that - there is a huge market for
> cheaper cameras - but they lost all credibility by trying to justify an
> economic argument with fake science.

it was a clever ad campaign that sounds good at first, but with a
little scrutiny, it's obvious it's bullshit.

[Kennedy McEwen]

In article <9pf9s9...@mid.individual.net>, Rol_Lei Nut
<Speleo_Ka...@yahoo.com> writes

>On 2/7/2012 14:12, Kennedy McEwen wrote:
>
>> OM lenses work just as well on digital as they did on film, which
>> doesn't mean telecentric lenses can't work better, but the argument was
>> false to begin with and was merely an attempt by Olympus to justify
>> their investment in cheap chips.
>
>I have a Panasonic M43 and use *lots* of made for film lenses on it
>(M42, Zeiss, Leica both M & R, M39 & others).
>
>Some lenses, especially fast one, often don't work well at their faster
>apertures (by "not well" I mean visibly less well than on a film
>camera).

Most lenses will exhibit vignetting when wide open. That has nothing
whatsoever to do with the sensor, whether digital or film, but due to
the exit pupil being truncated. You can see this happening just by
looking through the lens while tilting it - that circular aperture wide
open closes down to a "cat's eye" when significantly off axis. The
"cat's eye" is the main cause of the corner vignette. Stop the lens
down a little and tilting it has no effect on the aperture.

This was just the same with film as it is on a digital sensor - whether
you noticed it or not. Furthermore, stopping the lens down doesn't
change its telecentricity - so the very fact that you get a different
level of vignette fully open demonstrates that telecentricity isn't the
issue that Olympus claim(ed) it to be.

Lots of compact, allegedly useless on digital because they aren't
telecentric, OM lenses are used on Canon and other FF digital cameras
without problem, hence their used prices are holding up quite well.

Only this morning I was shooting with the Zuiko 18mm f/3.5, one of the
least telecentric lenses on the OM lineup due to the tiny rear pupil,
and it is extremely flat to the corners when stopped down to f/5.6 -
less than quarter a stop. Even fully open, it is only a stop down in
the corners - but I can see that looking through the lens, irrespective
of the sensor, since half the exit pupil is vignetted - nothing to do
with telecentricity. What I dislike about the Zuiko 18mm was the use of
an even number (6) of aperture blades, resulting in coarse specular
reflections and poor bokeh.

[Kennedy McEwen]

In article <2012020813350381290-pete3attkins@nospamntlworldcom>, Pete A

<pete3....@nospam.ntlworld.com> writes
>On 2012-02-08 00:57:00 +0000, Kennedy McEwen said:
>
>> In article <2012020714103581999-pete3attkins@nospamntlworldcom>, Pete
>>A <pete3....@nospam.ntlworld.com> writes
>>> On 2012-02-07 13:12:37 +0000, Kennedy McEwen said:
>>>
>>>> In article <kp62j7h2k806akg8h...@4ax.com>, Bruce
>>>><docne...@gmail.com> writes
>>>>> If there wasn't a problem, as you so confidently assert, why on earth
>>>>> would Olympus have gone to such lengths?
>>>>>
>>>> To justify making small 4-turds sensors in the first place!
>>>> That's when they came out with the "telecentric is best for
>>>>digital" myth in the first place and it was shortly proven to be
>>>>wrong by measurement. The light fall-off due to non-telecentricity
>>>>is *LESS* on Olympus (and Canon FF sensors for that matter) than
>>>>

>>> Illumination falloff for a non-telecentric lens is approximately a
>>>cosine to the fourth power. The only way a digital sensor can suffer
>>>_less_ falloff than film is by altering the angle of the non-central
>>>micro-lenses.
>> Wrong.
>> 3D microlens v's 2D flat film surface. A tennis ball has the same
>>cross section no matter what angle you view it from, while a flat
>>sheet of film has a cross section that is cos^2. Any 3D view of the
>>microlens means less than cos^4 fall-off.
>
>Half a tennis ball clearly reduces its cross section as the angle moves
>away from perpendicular.
>

By less than a flat sheet, and 3/4 of a tennis ball reduces even less.
Hence a microlensed sensor will usually have less fall-off than film.

>> Also, if the "image" from the micro-lens is smaller than the
>>sensitive area of the pixel, the illumination fall-off on a digital
>>sensor will *always* be less than film - by 2 of those four cosines!
>
>That is simply trading pixel sensitivity for pixel vignetting.

No it isn't. The purpose of those microlenses is to put the light from
the total pixel area into the sensitive area - having a smaller
sensitive area doesn't change the sensitivity of the pixel, although it
can result in lower saturation levels. Similarly, vignetting.

> There's a nice illustration on page 44 of the Leica M-Sytem Catalog
>(page 23 of the PDF):
>

A nice illustration that address a different issue, not this one. That
is showing what Leica have done to reduce light fall off even further
with very fast lenses.

>
>> Try measuring it, its not that difficult but too many folk would
>>prefer to regurgitate the dogma than find out the truth for
>>themselves! Alternatively, google my measurements from 5 or 6 years
>>ago where this was discussed to death - the Olympus dogma death!
>
>Most (D)SLRs work adequately with most lenses because the lens mount to
>sensor/film distance is relatively large. This requires wide-angle
>lenses to be retrofocus designs, which is also, in effect, performing
>the function of your tennis ball analogy. Indeed, a retrofocus
>wide-angle shows less light falloff with both film and digital.
>
>As an example, cos^4 of 33 degrees is 0.49, which is 1 f-stop of light
>falloff.

And the *measured* sensitivity for 40deg incidence on a Canon 5D sensor
was as much as 94.5% of the response at perpendicular, using linear
processing of RAW data. That's a little less than 0.2 stops - and a lot
less than cos^4, which film would be expected to approximate.

>Many lenses suffer more than 1-stop of corner vignetting (when
>wide-open) and this is generally considered to be acceptable.

Many lenses do indeed suffer corner vignetting - they do so
independently of the sensor and this is in addition to any cos^4 or
other terms due to the sensor.

[Rol_Lei Nut]

Wow! Speaking about ranting and a condescending attitude!

1) I never mentioned vignetting, as vignetting per se usually wasn't an
issue when I used film lenses on my M43.

2) At least on that particular M43 sensor and camera, the "bad" lenses
at the "bad" apertures gave much softer images than on film, exposure
errors (sometimes) and a general look as if they were badly flared (no,
they were not subjected to any backlighting which would cause that, at
least on film).

3) I have (quite) a bit of experience with lens testing and I had
rigorously tested all the lenses used on film.

4) You cannot compare different sensors to each other (or to film): each
will have a different behaviour with "difficult" lenses.

5) Maybe actually read people's posts more carefully....

[Pete A]

On 2012-02-08 16:23:43 +0000, Kennedy McEwen said:

> Pete A writes
>> Kennedy McEwen said:
>>
>>> Pete A writes
>>>> [...]

>>>> Illumination falloff for a non-telecentric lens is approximately a
>>>> cosine to the fourth power. The only way a digital sensor can suffer
>>>> _less_ falloff than film is by altering the angle of the non-central
>>>> micro-lenses.
>>> Wrong.
>>> 3D microlens v's 2D flat film surface. A tennis ball has the same
>>> cross section no matter what angle you view it from, while a flat sheet
>>> of film has a cross section that is cos^2. Any 3D view of the
>>> microlens means less than cos^4 fall-off.
>>
>> Half a tennis ball clearly reduces its cross section as the angle moves
>> away from perpendicular.
>>
> By less than a flat sheet, and 3/4 of a tennis ball reduces even less.
> Hence a microlensed sensor will usually have less fall-off than film.

Yeah right - adjacent lenses will not cast shadows just as eggs in an
egg tray are each visible from all angles. Last time I checked, they
weren't.

To me, this makes sense:

<http://www.olympus.co.uk/consumer/21693_7045.htm>

Surely, if what you are claiming is correct then film with a rough
surface will show less light falloff with angle than one with a smooth
surface.

>>> Also, if the "image" from the micro-lens is smaller than the sensitive
>>> area of the pixel, the illumination fall-off on a digital sensor will
>>> *always* be less than film - by 2 of those four cosines!
>>
>> That is simply trading pixel sensitivity for pixel vignetting.
> No it isn't. The purpose of those microlenses is to put the light from
> the total pixel area into the sensitive area - having a smaller
> sensitive area doesn't change the sensitivity of the pixel, although it
> can result in lower saturation levels. Similarly, vignetting.

If the micro-lenses are so small that they do not shadow each other
then they are far too small to receive the full illuminance i.e. the
available photons per unit area. Lenses do not magically amplify the
number of photons per unit area.

>> There's a nice illustration on page 44 of the Leica M-Sytem Catalog
>> (page 23 of the PDF):
>>
> A nice illustration that address a different issue, not this one. That
> is showing what Leica have done to reduce light fall off even further
> with very fast lenses.

Well, slow lenses and stopped-down lenses have a low angle of incidence
so there isn't a problem in the first place. So, what precisely is the
issue you are talking about?

>>> Try measuring it, its not that difficult but too many folk would prefer
>>> to regurgitate the dogma than find out the truth for themselves!
>>> Alternatively, google my measurements from 5 or 6 years ago where this
>>> was discussed to death - the Olympus dogma death!
>>
>> Most (D)SLRs work adequately with most lenses because the lens mount to
>> sensor/film distance is relatively large. This requires wide-angle
>> lenses to be retrofocus designs, which is also, in effect, performing
>> the function of your tennis ball analogy. Indeed, a retrofocus
>> wide-angle shows less light falloff with both film and digital.
>>
>> As an example, cos^4 of 33 degrees is 0.49, which is 1 f-stop of light falloff.
>
> And the *measured* sensitivity for 40deg incidence on a Canon 5D sensor
> was as much as 94.5% of the response at perpendicular, using linear
> processing of RAW data. That's a little less than 0.2 stops - and a
> lot less than cos^4, which film would be expected to approximate.

Just goes to show that my D700 is a total pile of crap compared to a 5D.

>> Many lenses suffer more than 1-stop of corner vignetting (when
>> wide-open) and this is generally considered to be acceptable.
>
> Many lenses do indeed suffer corner vignetting - they do so
> independently of the sensor and this is in addition to any cos^4 or
> other terms due to the sensor.

Of course, and these other limitations will be clearly revealed in the
lens bokeh.

"Near telecentric" does not mean "telecentric". It just means that
retrofocus (more precisely, reverse telephoto) is a lens design issue
that must be considered for small area pixels/sensels. The problem is
exacerbated by the fact that the depth of a pixel cannot be scaled: the
depth determines the probability of a photon being detected in the
material used for detection. As pixel area reduces, the depth must be
maintained therefore "tunnel vision" increases - the angle of
acceptance reduces. It is right and proper that small high-resolution
sensors have lenses designed with this factor in mind. It seems to me
that Olympus took a very bold step by attempting to define a standard
for competitors to follow. Third party lenses (and editing software)
for Nikon and Canon have to be created by reverse engineering, which
isn't exactly what the consumer wants.

I have no wish to dispel your convictions or discredit your
measurements. Quite the reverse - let's all enjoy photography despite
the endless marketing bullshit that surrounds it. Great photos usually
result from being in the right place at the right time rather than
debating the laws of physics and optics. Knowledge helps - yep, I've
ruined many a shot by choosing the wrong aperture and many more shots
by failing to pack the most suitable lenses for the subject. Hindsight
can be both a blessing and a curse.

[Pete A]

If a lens is rear telecentric then its rays are parallel i.e. the angle
of incidence is zero. Stopping it down cannot reduce the angle of
incidence any further. For a non-telecentric lens, of course stopping
it down reduces the angle of incidence thereby making it _nearer to_
rear telecentric than when it is wide-open.

> Lots of compact, allegedly useless on digital because they aren't
> telecentric, OM lenses are used on Canon and other FF digital cameras
> without problem, hence their used prices are holding up quite well.
>
> Only this morning I was shooting with the Zuiko 18mm f/3.5, one of the
> least telecentric lenses on the OM lineup due to the tiny rear pupil,

Hang on a minute - a tiny rear exit pupil ensures that rays will not
strike the sensor/film at an oblique angle, therefore how can it be one
of the least telecentric lenses in the OM lineup?

[Kennedy McEwen]

In article <2012020818474816746-pete3attkins@nospamntlworldcom>, Pete A
<pete3....@nospam.ntlworld.com> writes

>On 2012-02-08 16:23:43 +0000, Kennedy McEwen said:
>
>> Pete A writes
>>> Kennedy McEwen said:
>>>
>>>> Pete A writes
>>>>> [...]
>>>>> Illumination falloff for a non-telecentric lens is approximately a
>>>>>cosine to the fourth power. The only way a digital sensor can
>>>>>suffer _less_ falloff than film is by altering the angle of the
>>>>>non-central micro-lenses.
>>>> Wrong.
>>>> 3D microlens v's 2D flat film surface. A tennis ball has the same
>>>>cross section no matter what angle you view it from, while a flat
>>>>sheet of film has a cross section that is cos^2. Any 3D view of
>>>>the microlens means less than cos^4 fall-off.
>>> Half a tennis ball clearly reduces its cross section as the angle
>>>moves away from perpendicular.
>>>
>> By less than a flat sheet, and 3/4 of a tennis ball reduces even
>>less. Hence a microlensed sensor will usually have less fall-off than
>>film.
>
>Yeah right - adjacent lenses will not cast shadows just as eggs in an
>egg tray are each visible from all angles. Last time I checked, they
>weren't.
>

But they *are* better than a flat surface, which is what matters in this
discussion.

>To me, this makes sense:
>
><http://www.olympus.co.uk/consumer/21693_7045.htm>
>

Top some extent it does, but several features are exaggerated to sell
the Olympus myth. However, the edge of field example shows precisely
the effect I explained above - a reduction of the cosine law due to the
spherical surface of the microlens.

>Surely, if what you are claiming is correct then film with a rough
>surface will show less light falloff with angle than one with a smooth
>surface.

Yes. If only there were any *films* with rough surfaces.

>
>>>> Also, if the "image" from the micro-lens is smaller than the
>>>>sensitive area of the pixel, the illumination fall-off on a
>>>>digital sensor will *always* be less than film - by 2 of those
>>>>four cosines!
>>> That is simply trading pixel sensitivity for pixel vignetting.
>> No it isn't. The purpose of those microlenses is to put the light
>>from the total pixel area into the sensitive area - having a smaller
>>sensitive area doesn't change the sensitivity of the pixel, although
>>it can result in lower saturation levels. Similarly, vignetting.
>
>If the micro-lenses are so small that they do not shadow each other
>then they are far too small to receive the full illuminance i.e. the
>available photons per unit area.

That isn't true. It isn't the size of the microlenses that matters, it
is their aspect ratio. ie. height to pitch. (As shown on the same
Olympus page you referenced above!) Of course, the retention of angular
response due to the microlenses eventually falls off, with the response
being much worse than a flat surface at extreme angles of incidence.
However such angles would only occur with lenses of very short focal
lengths and backworking distances - the tiny 4-turds sensor with its
consequential x2 focal length factor makes the problem worse!

>
>>> There's a nice illustration on page 44 of the Leica M-Sytem Catalog
>>>(page 23 of the PDF):
>>>
>> A nice illustration that address a different issue, not this one.
>>That is showing what Leica have done to reduce light fall off even
>>further with very fast lenses.
>
>Well, slow lenses and stopped-down lenses have a low angle of incidence
>so there isn't a problem in the first place.

Not so. Slow and stopped down lenses have peripheral rays with a lower
spread of angles around the principle ray than fast lenses wide open,
however that has nothing to do with the angle of the principle rays
themselves. Telecentric lenses have principle rays with zero angle of
incidence (perpendicular to the focal plane), the greater the angle of
the principle ray at the corner of the image the less telecentric the
lens is. Stopping a non-telecentric lens down increases the angle of
incidence of exactly as many peripheral rays at the corner of the image
as it decreases - the effect cancel out in all but ridiculously extreme
conditions which cannot be achieved in any 35mm SLR design.

>So, what precisely is the issue you are talking about?
>

The angle of incidence of the principle rays to each point in the image
- departure from telecentricity, the great Satan that Olympus would have
you believe corrupts all large sensors.

>>>> Try measuring it, its not that difficult but too many folk would
>>>>prefer to regurgitate the dogma than find out the truth for
>>>>themselves! Alternatively, google my measurements from 5 or 6
>>>>years ago where this was discussed to death - the Olympus dogma death!
>>> Most (D)SLRs work adequately with most lenses because the lens
>>>mount to sensor/film distance is relatively large. This requires
>>>wide-angle lenses to be retrofocus designs, which is also, in
>>>effect, performing the function of your tennis ball analogy. Indeed,
>>>a retrofocus wide-angle shows less light falloff with both film and digital.
>>> As an example, cos^4 of 33 degrees is 0.49, which is 1 f-stop of
>>>light falloff.
>> And the *measured* sensitivity for 40deg incidence on a Canon 5D
>>sensor was as much as 94.5% of the response at perpendicular, using
>>linear processing of RAW data. That's a little less than 0.2 stops -
>>and a lot less than cos^4, which film would be expected to approximate.
>
>Just goes to show that my D700 is a total pile of crap compared to a 5D.
>

I have no objective measurements of a D700, let alone yours, but
subjectively it doesn't look any worse. Having said that, the 5DII has
slightly more angular light fall off - but still less than flat film.

>>> Many lenses suffer more than 1-stop of corner vignetting (when
>>>wide-open) and this is generally considered to be acceptable.
>> Many lenses do indeed suffer corner vignetting - they do so
>>independently of the sensor and this is in addition to any cos^4 or
>>other terms due to the sensor.
>
>Of course, and these other limitations will be clearly revealed in the
>lens bokeh.
>
>"Near telecentric" does not mean "telecentric".

I didn't claim it was. The fact is that many lenses in Olympus 4-turds
range are no more telecentric than their OM equivalents despite the
smaller sensor size. Whether near telecentric or less telecentric is
all relative to sensor size.

[Kennedy McEwen]

In article <2012020819270899904-pete3attkins@nospamntlworldcom>, Pete A
<pete3....@nospam.ntlworld.com> writes

How can an image form with parallel rays? It is the *principle* rays
which are parallel in a telecentric lens, not all the rays and certainly
not the peripheral rays which determine the f/#.

If what you claimed was true then any pinhole lens would be telecentric
- which is certainly not the case.

>Stopping it down cannot reduce the angle of incidence any further. For
>a non-telecentric lens, of course stopping it down reduces the angle of
>incidence thereby making it _nearer to_ rear telecentric than when it
>is wide-open.
>

Stopping a non-telecentric lens down does not change the angle of
incidence of the principle rays to any point on the focal plane. Thus,
by definition, stopping a lens down does *NOT* make a lens "nearer to"
telecentric in any way.

>> Lots of compact, allegedly useless on digital because they aren't
>>telecentric, OM lenses are used on Canon and other FF digital cameras
>>without problem, hence their used prices are holding up quite well.
>> Only this morning I was shooting with the Zuiko 18mm f/3.5, one of
>>the least telecentric lenses on the OM lineup due to the tiny rear
>>pupil,
>
>Hang on a minute - a tiny rear exit pupil ensures that rays will not
>strike the sensor/film at an oblique angle
>

Only close to the optic axis, ie. in the centre of the frame. A tiny
exit pupil ensures that the principle rays at the corner of the frame
strike the focal plane at a *much* more oblique angle than those at the
centre of the frame. To be telecentric, the principle rays for each
image point in the frame are parallel - a small rear element, only
slightly larger than the on-axis pupil, ensures that they are not.

>, therefore how can it be one of the least telecentric lenses in the OM
>lineup?

That paradox in your theory is something for you to ponder. There is no
paradox in mine.

One of the benefits of telecentricity is that geometric distortion is
minimised and objects remain the same size as the focus travels through
them. The design of the OM series Zuiko 18mm maximises both of these
effects, the object field magnifies at close focus and shrinks as focus
moves to infinity. Exaggerated geometry, not to be confused with the
exaggerated perspective due to the short focal length, was a selling
feature of that lens - achieved by its extremely non-telecentric design.

[Trevor]

"Bruce" <docne...@gmail.com> wrote in message

news:pvg4j79582691t2sa...@4ax.com...

>>
>>I only suggested it didn't match my experience and you have now explained
>>why. Thank you!
>
>
> You're welcome. But I didn't add anything that wasn't already in the
> post you decided not to read. ;-)

So show me where you previously mentioned the use of Kodak sensors which my
Canon doesn't have, and possibly explains why I don't have the problems you
are sure exist with the Olympus cameras.

Trevor.

[Bruce]

This is like trying to have a conversation with a wasp.

[RichA]

On Feb 8, 11:30 am, Kennedy McEwen <r...@nospam.demon.co.uk> wrote:
> In article <9pf9s9Fl8...@mid.individual.net>, Rol_Lei Nut
> <Speleo_Karstlens...@yahoo.com> writes

I think there is more to this than just telecentricity. I tested an
85mm f2.0 OM lens on a m4/3rds camera and it vignetted, right down to
f5.6.
If an 18mm OM doesn't vignette horribly on a FF, then something else
is at work.

[Bruce]

I find this discussion highly entertaining because it is the blind
leading the blind.

The suggestion that the least telecentric lenses are always those with
tiny rear elements is completely risible. In some cases, they are
among the *most* telecentric!

The implied converse, that a larger rear element means the lens is
closer to telecentric is *complete nonsense*. It is extremely naive
to assume that because the size of the rear element is closer to the
size of the sensor, that the rays must be emerging almost parallel to
each other and therefore perpendicular to the sensor. Once again, the
truth can be the exact opposite, because a larger rear element can
allow light rays to emerge at *more* oblique angles!

That might appear counter-intuitive to some, but that merely
demonstrates that intuition is highly subjective, and often wrong.

[Kennedy McEwen]

In article <44n7j7ptitm8bg2ep...@4ax.com>, Bruce
<docne...@gmail.com> writes

>
>The suggestion that the least telecentric lenses are always those with
>tiny rear elements is completely risible.

Nobody said that is *always* the case.
I gave an example, which is certainly the most common situation, where
it *IS* the case.

>In some cases, they are
>among the *most* telecentric!

That is a completely ridiculous statement - we can all restrict our
comparisons to the "some cases" which *can* be worse. In most cases
that is NOT the case. I referred to the entire OM range.

There are many aspects of the OM 18mm which demonstrate it's poor
telecentricity. However poor rear telecentricity is guaranteed
*because* it has a small rear element. That, together with the proximity
of the rear element to the focal plane (it projects into the lens mount
and just clears the mirror!), restricts the angle of incidence of the
principle rays at the corners of the focal plane to very oblique angles:
the very problem that Olympus claim makes such a non-telecentric lens
unsuitable for digital. Yet it works extremely well and is one of the
most sought after OM Zuikos for FF dSLRs!

>
>The implied converse, that a larger rear element means the lens is
>closer to telecentric is *complete nonsense*.

That is *not* the implied converse. Only an idiot thinks that "all cats
are furry animals" implies "all furry animals are cats"!

The converse is that telecentricity, more specifically
rear-telecentricity which is the version under discussion here,
*requires* a large rear element!

Should Bruce Almighty dispute that, I am sure he can point us to a ray
diagram which shows otherwise. (That doesn't mean a diagram showing that
telecentricity *can* be worse on a large rear element design, that is
obvious with the standard textbook design of a front-telecentric lens
being such an example.)

[Pete A]

Indeed, the principle ray contains no light whatsoever because it's
infinitely thin. Yes, the aperture affects the cone of peripheral rays.

> If what you claimed was true then any pinhole lens would be telecentric
> - which is certainly not the case.

A pinhole camera exhibits cos^4 light falloff at the film. Having a
very small aperture results in a correspondingly small cone therefore
it is primarily the angle of the principle ray that causes the light
falloff in such a camera. At 33 degrees the falloff is 1 f-stop.

With an image-side (rear) telecentric lens, it is only the angle of the
cone that causes light falloff. The cone does not vary across the image
plane therefore the image doesn't suffer from corner vignetting. If the
lens is badly designed then mechanical vignetting may cause light
falloff in the image corners.

Very wide-angle lenses suffer from light falloff on the object side,
but this is a separate issue.

In any mirror-less system, the lens designer is free to position the
exit pupil very close to the image plane, which places an unrealistic
demand on the design of image sensors; especially Bayer CFA sensors.
Specifying "near-telecentric" simply means placing the exit pupil
_reasonably_ far away from the sensor. So, it is a big issue and
perfectly warranted in a mirror-less system specification.

>> Stopping it down cannot reduce the angle of incidence any further. For
>> a non-telecentric lens, of course stopping it down reduces the angle of
>> incidence thereby making it _nearer to_ rear telecentric than when it
>> is wide-open.
>>
> Stopping a non-telecentric lens down does not change the angle of
> incidence of the principle rays to any point on the focal plane. Thus,
> by definition, stopping a lens down does *NOT* make a lens "nearer to"
> telecentric in any way.

Literally, you are correct. In essence, stopping down reduces the rays
that are problematic to the sensor.

>>> Lots of compact, allegedly useless on digital because they aren't
>>> telecentric, OM lenses are used on Canon and other FF digital cameras
>>> without problem, hence their used prices are holding up quite well.
>>> Only this morning I was shooting with the Zuiko 18mm f/3.5, one of the
>>> least telecentric lenses on the OM lineup due to the tiny rear pupil,
>>
>> Hang on a minute - a tiny rear exit pupil ensures that rays will not
>> strike the sensor/film at an oblique angle
>>
> Only close to the optic axis, ie. in the centre of the frame. A tiny
> exit pupil ensures that the principle rays at the corner of the frame
> strike the focal plane at a *much* more oblique angle than those at the
> centre of the frame. To be telecentric, the principle rays for each
> image point in the frame are parallel - a small rear element, only
> slightly larger than the on-axis pupil, ensures that they are not.

The tiny exit pupil you mentioned is not the problem. The distance of
the exit pupil from the image plane is the problem.

>> , therefore how can it be one of the least telecentric lenses in the OM lineup?
> That paradox in your theory is something for you to ponder. There is
> no paradox in mine.

There is no paradox, you misstated cause and effect. That isn't a
criticism - I frequently write things that make sense only to me.

> One of the benefits of telecentricity is that geometric distortion is
> minimised and objects remain the same size as the focus travels through
> them. The design of the OM series Zuiko 18mm maximises both of these
> effects, the object field magnifies at close focus and shrinks as focus
> moves to infinity. Exaggerated geometry, not to be confused with the
> exaggerated perspective due to the short focal length, was a selling
> feature of that lens - achieved by its extremely non-telecentric design.

That sounds like a very interesting lens.

[Mike]

Why would a user of the 24x36mm OM-1/2/3/4 be anxious for a 1/4 frame
(17.3 x 13 mm) look-a-like?


--
Mike

[Kennedy McEwen]

In article <2012020918152437271-pete3attkins@nospamntlworldcom>, Pete A

<pete3....@nospam.ntlworld.com> writes
>On 2012-02-08 23:44:00 +0000, Kennedy McEwen said:
>
>> In article <2012020819270899904-pete3attkins@nospamntlworldcom>, Pete
>>A <pete3....@nospam.ntlworld.com> writes

>>> If a lens is rear telecentric then its rays are parallel i.e. the
>>>angle of incidence is zero.
>> How can an image form with parallel rays? It is the *principle*
>>rays which are parallel in a telecentric lens, not all the rays and
>>certainly not the peripheral rays which determine the f/#.
>
>Indeed, the principle ray contains no light whatsoever because it's
>infinitely thin. Yes, the aperture affects the cone of peripheral rays.
>

Of course it does, but those peripheral rays don't affect the
telecentricity. It is the angle of the principle rays which determine
that.

>
>> If what you claimed was true then any pinhole lens would be
>>telecentric - which is certainly not the case.
>
>A pinhole camera exhibits cos^4 light falloff at the film. Having a
>very small aperture results in a correspondingly small cone therefore
>it is primarily the angle of the principle ray that causes the light
>falloff in such a camera. At 33 degrees the falloff is 1 f-stop.
>
>With an image-side (rear) telecentric lens, it is only the angle of the
>cone that causes light falloff. The cone does not vary across the image
>plane therefore the image doesn't suffer from corner vignetting.
>

Exactly what I said previously! A pinhole lens is NOT telecentric - the
narrow cone angle of the high f/# does not affect the telecentricity of
a lens, which is determined by angle of the principle rays to each point
on the image plane.

>In any mirror-less system, the lens designer is free to position the
>exit pupil very close to the image plane, which places an unrealistic
>demand on the design of image sensors; especially Bayer CFA sensors.
>Specifying "near-telecentric" simply means placing the exit pupil
>_reasonably_ far away from the sensor. So, it is a big issue and
>perfectly warranted in a mirror-less system specification.
>

We are discussing the use of OM series lenses in particular, which were
not mirrorless cameras, and lenses from other film SLR cameras in
general. So the issue of "placing an exit pupil close to the image
plane" is irrelevant. Nevertheless, the same constraints on lens
designs existed for mirrorless film cameras, such as Leica rangefinders.
Furthermore, the lens specification for the 4-turds standard required
compatibility with dSLRs as well, so that standard has the same
restriction on rear element position as well. Olympus claimed they had
to use small sensors because digital sensors in dSLRs required
telecentric optics to work properly and the lenses designed for film
would not cope with full size digital sensors. That was a lie and
remains demonstrably so by anyone with an OM adapter and a FF dSLR.

>> Stopping a non-telecentric lens down does not change the angle of
>>incidence of the principle rays to any point on the focal plane. Thus,
>>by definition, stopping a lens down does *NOT* make a lens "nearer to"
>>telecentric in any way.
>
>Literally, you are correct. In essence, stopping down reduces the rays
>that are problematic to the sensor.
>

It reduces just as many rays that are less oblique, and thus *less
problematic*, as it does rays that are more oblique than the principle
ray - it has no effect on the telecentricity or the response of the
sensor. The change in light fall-off when stopping down is almost
entirely a consequence of the exit pupil being partially obscured when
fully open, not the angle of incidence of the principle rays - they
remain fixed.

>
>The tiny exit pupil you mentioned is not the problem. The distance of
>the exit pupil from the image plane is the problem.
>

You can't place a larger rear element any closer to the focal plane on
an SLR without obstructing the mirror, consequently the 18/3.5 is "one
of the least telecentric lenses in the OM series" due to its small rear
element. If the lens design utilised a larger convergent rear element
it could be placed at exactly the same distance with better
telecentricity - so it *is* the size that makes this lens "one of the
least telecentric lenses in the OM lineup".

>
>>> , therefore how can it be one of the least telecentric lenses in the
>>>OM lineup?
>> That paradox in your theory is something for you to ponder. There is
>>no paradox in mine.
>
>There is no paradox, you misstated cause and effect.

I have re-read exactly what I wrote and I certainly did NOT mis-state
cause and effect. On the contrary, you claimed that "a tiny rear exit
pupil *ensures* that rays will not strike the sensor/film at an oblique
angle" which is not only confusing cause and effect but also wrong!
However, this shouldn't degrade to a "he said, she said" issue, the fact
remains that telecentricity or the lack of it in lenses designed for
film has no more effect on the solid state sensors in modern digital
cameras than it did on film.

>
>> One of the benefits of telecentricity is that geometric distortion is
>>minimised and objects remain the same size as the focus travels
>>through them. The design of the OM series Zuiko 18mm maximises both
>>of these effects, the object field magnifies at close focus and
>>shrinks as focus moves to infinity.
>

>That sounds like a very interesting lens.
>

All non-telecentric lenses exhibit this effect to some degree. In fact
it is one of the simplest tests of rear telecentricity - fill the frame
with a subject and pull focus from closest point through to infinity. If
the object remains the same size independent of the focus position (the
distance of the lens from the focal plane) then the lens is rear
telecentric. The more that image size changes, and hence geometry is
distorted, with focus the less telecentric the lens is.

[Rol_Lei Nut]

On 2/9/2012 19:50, Mike wrote:
> Why would a user of the 24x36mm OM-1/2/3/4 be anxious for a 1/4 frame
> (17.3 x 13 mm) look-a-like?
>

Not anxious, but there are things to like: "Free film" (well, once
you've more or less heavily invested in equipment and any necessary
peripherals), "instant developing" (though if you shoot raw that also
takes some time & most images can use some adjusting before printing or
viewing), some quite decent lenses (some of the very few WA zooms I've
found to be good - I normally use Zeiss & Leica with film) and very
compact and light (even compared to the original OM series).

What I like less it that the "form follows function" idea got lost in
translation and the useless false pentraprism adds quite a bit to the
effective size of the camera.
Also the hand grips seem to be a lame attempt to label the camera as a
"pro" model (marketing predominating over content).
Perhaps Olympus should introduce some oversized white telephoto lenses
which can be parked at the side of sport fields, then they'd have
succeeded in emulating the ultimate marketing brand....

That said, if the image quality is as good as it should be and the
camera seems tough enough, I'll probably end up buying one when they get
affordable. A water resistant, tough (hopefully) camera with decent (or
hopefully more than decent) quality and tiny but good lenses is
something to like.

But I'll still use my film Leicas and Rolleiflexes when I want to do
something special...

[Eric Stevens]

On Thu, 09 Feb 2012 14:55:37 +0000, Bruce <docne...@gmail.com>
wrote:

http://www.opto-engineering.com/telecentric-lenses-tutorial.html may
be of some help.

>The suggestion that the least telecentric lenses are always those with
>tiny rear elements is completely risible. In some cases, they are
>among the *most* telecentric!
>
>The implied converse, that a larger rear element means the lens is
>closer to telecentric is *complete nonsense*. It is extremely naive
>to assume that because the size of the rear element is closer to the
>size of the sensor, that the rays must be emerging almost parallel to
>each other and therefore perpendicular to the sensor. Once again, the
>truth can be the exact opposite, because a larger rear element can
>allow light rays to emerge at *more* oblique angles!
>
>That might appear counter-intuitive to some, but that merely
>demonstrates that intuition is highly subjective, and often wrong.
>
>

Regards,

Eric Stevens

[Pete A]

The axe that you are grinding is with Olympus. My condoning of Olympus
recommendations for practical reasons obviously irritates you - this is
obvious not by your replies, it is obvious from what you snip from my
replies.

Enjoy your photography.

[Pete A]

On 2012-02-09 20:12:27 +0000, Eric Stevens said:

Thanks Eric.

Some may find these interesting:

<http://www.pco.de/fileadmin/user_upload/db/download/pco_cooKe_kb_shading_0603_s.pdf>


<http://en.wikipedia.org/wiki/Vignetting>

<http://toothwalker.org/optics/vignetting.html>

>
>> The suggestion that the least telecentric lenses are always those with
>> tiny rear elements is completely risible. In some cases, they are
>> among the *most* telecentric!
>>
>> The implied converse, that a larger rear element means the lens is
>> closer to telecentric is *complete nonsense*. It is extremely naive
>> to assume that because the size of the rear element is closer to the
>> size of the sensor, that the rays must be emerging almost parallel to
>> each other and therefore perpendicular to the sensor. Once again, the
>> truth can be the exact opposite, because a larger rear element can
>> allow light rays to emerge at *more* oblique angles!
>>
>> That might appear counter-intuitive to some, but that merely
>> demonstrates that intuition is highly subjective, and often wrong.

I totally agree with Bruce. A true bi-telecentric (afocal) lens demands
a front element somewhat larger than the object and a rear element
somewhat larger than the sensor; a near-telecentric image-space lens
has no such demands. Very few people can reverse-engineer a lens just
by looking at it and jumping to intuitive conclusions :-)