Long lens options
Don Stauffer
we'd like a longer option. I don't want to spend a lot of money, 'cause
we wouldn't use it that often.
Which do folks think would have better performance- a 2X converter, or
one of those 600mm "mirror" lenses?
Does anyone know what optical configuration those mirror lenses are- are
they Cassegrains, or Newtonians (flat folding lens), or something
entirely different?
DD-Diver
"M-M" <nospa...@ny.more> schreef in bericht
news:nospam.m-m-9837C...@cpe-76-190-186-198.neo.res.rr.com...
> In article <49a80743$0$87068$815e...@news.qwest.net>,
> The aperture will be about the same but the bokeh on a mirror lens is
> horrific.
>
> --
> m-m
> http://www.mhmyers.com
For one, the "bokeh" is horrific, for me, it was exactly that donut-shape of
unsharp spots that made buy one (Sigma 600), it gives great creative
possibilities.
OP: "mirrors" are catadioptric,see also:
http://photo.net/learn/optics/mirrors/ ...article dates from 2003.
"mirrors" are manual focus only, and have a fixed aparture. Decades ago
Pentax made a 400-600 mirror zoom.., actually, there is one on E-Bay right
now. I would love to have something like that for my Canon!
If your current setup is compatible with a 2x-converter, I would try that
option first, probably a lot cheaper, and you can aways sell the converter
later.
L.
Marcin
Samyang 500mm MC f/5,6 - about 100 EUR !!! (nikon, canon, sony, pentax)
Samyang 650-1300mm IF MC f/8,0-16,0 Canon - about 150 EUR !!!!!!
I don't have information about quality of that product because is brand new
on the Polish market.
Test photos you can download here:
http://www.optyczne.pl/1607-nowo%C5%9B%C4%87-Samyang_85_mm_f_1.4_Aspherical_IF_-_przyk%C5%82adowe_zdj%C4%99cia.html
Best Regards
Marcin
www.gorgolewski.com
Uzytkownik "Don Stauffer" <stau...@usfamily.net> napisal w wiadomosci
news:49a80743$0$87068$815e...@news.qwest.net...
semoi
Mirror lenses are difficult to focus.
Repeat until you comprehend why there are so many used mirror lenses
available.
TheRealSteve
On Fri, 27 Feb 2009 13:42:51 -0800, "semoi" <fac...@hotmail.com>
wrote:
Are mirror lenses any more difficult to focus than a reflector
telescope?
Rich
news:75vgq49riv47r56ml...@4ax.com:
Not really. Moving a primary mirror in a Cassegrain with a fine screw
(which is how they work, except for those that use barrel focusing like
camera lenses which reposition the corrector lens up front to achieve
focus) is no more difficult than using a rack and pinion focuser on a
Newtonian telescope. The problems arise when the mirror system is junk
(Sigma) because it makes focus difficult to achieve. Because of the
extreme focal lengths (often 1000mm or more) they tend to mush through
focus if the optics suck.
If you can't afford a long refractor camera lens, then a good substitute
is a refractor telescope because it will allow a relatively fast f-ratio
(relative to long focal length mirror lenses) and generally much better
image quality.
Here are two good ones:
770mm f7.0
http://www.telescope.com/control/product/~category_id=refractors/
~pcategory=telescopes/~product_id=09206
430mm f6.0:
http://www.telescope.com/control/product/~category_id=refractors/
~pcategory=telescopes/~product_id=09781
sligoNo...@hotmail.com
They are Cassegrain. Unless you are going to go for an rather
expensive one, I would not bother with a 2X converter. Most just
don't have the quality to work well with a converter.
sligoNo...@hotmail.com
wrote:
>Mirror lenses are difficult to focus.
I never found mine difficult to focus but I can't recommend
then in general because except for the very expensive high quality
ones they just don't have the quality IMO.
jaf
They must be held rock steady.
ANY movement will make the picture appear blurry or out of focus.
John
"semoi" <fac...@hotmail.com> wrote in message news:A7Zpl.17943$yr3....@nlpi068.nbdc.sbc.com...
Chris Malcolm
Except for those which autofocus, like the Minolta/Sonys.
--
Chris Malcolm
Alfred Molon
> Except for those which autofocus, like the Minolta/Sonys.
Which ones specifically?
--
Alfred Molon
http://www.molon.de - Photos of Asia, Africa and Europe
Bob Williams
Don, I bought a 500mm, f8.0 Vivitar Mirror lens for my Canon A-1 film
camera and was very disappointed in the results.
Mirror lenses have only one f-stop (f8.0 in this case).
At f8.0 it is VERY difficult to focus accurately even in bright sunlite.
At low light levels it was almost impossible to focus accurately.
My canon A-1 has a split image focusing aid. At f8.0, one side of the
aid tends to go black as you try to focus.
Perhaps a DSLR with a different focusing aid could do better.
But I would ABSOLUTELY try it out on your camera before buying it.
The configuration of this Vivitar Mirror lens is Cassegrain
Bob Williams
Charles
<stau...@usfamily.net> wrote:
The old Vivitar Series 1 600 Cat was a Matsutov, or something like
that. Similar to a Cassegrain.
Don Stauffer
What I meant was one or the other. That is, a 2X converter with my
300mm lens, or a 600mm mirror lens. Which would have the best optical
performance?
David Ruether
"Don Stauffer" <stau...@usfamily.net> wrote in message news:49a95282$0$87065$815e...@news.qwest.net...
Only the very best non-zoom (or perhaps one or two
zooms, like the Nikkor 200-400mm f4, which you do
not own...) work well on a 2x, and then only if the
converter is VERY high quality (like Nikon and Canon
top-end converters) AND a good match for the lens
(like Nikon and Canon top-end fast tele lenses - but the
Nikon 300mm f4.5 ED non-IF also worked very well
on a TC300...). Otherwise, the very few best mirrors
(like the Nikon older-version barrel-focus 500mm f8)
will be superior - if used with understanding and care.
Keep in mind also that a decent 400mm (or good zoom
that includes 400mm) with a good 1.4X will also likely
be superior to a 300mm with a 2X. If you use Nikon,
look for the 500mm f8 Nikkor mirror described (it is a
"gem"), and put up with its "bad bokeh" (which actually
helps to make its images look sharper and more
contrasty). Most other mirrors are not very good, but
there are interesting exceptions, like the 350mm f5.6
Tamron and the 250mm f5.6 Minolta - but these
don't get you the length you are after, although they do
have the advantage of being very compact. BTW, all
mirrors are "slower" than rating (and they are mostly
slow to begin with...), but adding a TC14/14B to the
Nikkor mirror gives a still-sharp 700mm "f11" (too slow
to hand-hold except in unusually bright light, but I've
gotten good images with it with sun reflected off ice
and water with people/boats/etc. in silhouette and with
sky events - or other things by using a tripod).
--DR
sligoNo...@hotmail.com
<stau...@usfamily.net> wrote:
.
>
>
>What I meant was one or the other. That is, a 2X converter with my
>300mm lens, or a 600mm mirror lens. Which would have the best optical
>performance?
That would be difficult to say. There could be a lot of
overlap. It would really depend on the specific lens combinations.
All else being equal the mirror lens has optical disadvantages, but a
good one can still outshine a moderate quality single focal length
lens or a good quality zoom.
The only way I could pick one over the other is by testing
them, and then it would be best to test the actural samples you are
considering. I have noticed that there seems to be wide differences
in results from one sample mirror lens to another of the same model
compared to single focal length lenses.
Paul Furman
What sort of shooting will you use this for?
Birds in the back yard with a tripod?
Hiking & traveling?
--
Paul Furman
www.edgehill.net
www.baynatives.com
all google groups messages filtered due to spam
Ray Fischer
A couple of additional points ...
1) They're all Cassegrains, usually Schmidt Cassegrain.
2) Because of the secondary mirror they have lower contrast
3) Because of the secondary mirror they produce donuts in out-of-focus
highlights.
4) They're slow, typically with a maximum aperture of f6
5) Many don't have autofocus
6) Many don't have aperture adjustment (as in f8 ONLY).
But, on the plus side, they're way cheaper than the equivalent
telephoto non-mirror lens. As is so often the case, you get what
you pay for.
--
Ray Fischer
rfis...@sonic.net
trevor thomas
wrote:
>Don Stauffer wrote:
>> My wife and I both have zooms that go out to 300mm, but occasionally
>> we'd like a longer option. I don't want to spend a lot of money, 'cause
>> we wouldn't use it that often.
>>
>> Which do folks think would have better performance- a 2X converter, or
>> one of those 600mm "mirror" lenses?
>>
>> Does anyone know what optical configuration those mirror lenses are- are
>> they Cassegrains, or Newtonians (flat folding lens), or something
>> entirely different?
>
>Don, I bought a 500mm, f8.0 Vivitar Mirror lens for my Canon A-1 film
>camera and was very disappointed in the results.
>Mirror lenses have only one f-stop (f8.0 in this case).
>At f8.0 it is VERY difficult to focus accurately even in bright sunlite.
>At low light levels it was almost impossible to focus accurately.
>My canon A-1 has a split image focusing aid. At f8.0, one side of the
>aid tends to go black as you try to focus.
That's not caused by the size of the aperture but the focal-length of the
lens and the angle of the light-rays hitting the focusing screen.
As example, special focusing screens for the Olympus line of SLR cameras
were designed with specific optical applications in mind. I particularly
like my 100% clear one with the shorter focal-length fresnel lens for
microscopy and astrophotography purposes. It provides for an ultra-bright
display with little to no light loss for those applications, independent of
whatever focal-length is providing the image. There was a whole line of
specialty focusing screens for Olympus SLR cameras at one point (and may
still be). Ones for wide-angle lenses, telephoto lenses, microscopy
applications, etc. Olympus was bright enough to know that you had to match
the focusing screen to the optics used for imaging. The darkening that you
see is due to the angle of the imaging light-path and the way it is
entering the focus-assist prism surface, not the light intensity. It would
still be dark on one limb of that focusing area even if you were pointing
it at the sun. This is also due to the micro-fresnel lens' focal-length
mounted to the surface of your focusing screen. It can't focus on the main
lens' virtual image light-path as presented by the longer focal-length
lenses.
This is why fixed focusing screens in SLR-like cameras designed to accept a
wide array of optical components is just plain foolish. Those who buy
cameras with fixed focusing screens, never realizing they have to be
matched with the lenses in use, are even more foolish. Not only does the
lens' focal-length change the camera's exposure metering accuracy but so
too the ability to focus. Unless the focusing screen is matched to the
right focal length lens your exposure and focusing will always be a
crap-shot.
There's a lot of foolish camera buyers out there who don't know the first
thing about the principles of optics and how their cameras work. They buy
what they are told to buy, by those even less informed and less educated,
never knowing the difference. Nor do they comprehend why their exposures
are always off and then have to depend on RAW image formats to try to fix
what their lousy one-optical-path-fits-all optics created in the first
place.
Bob Williams
a 400 mm f4.5 tele lens (refractor) and never had any kind of focusing
problem with it. Focusing was done "Wide Open" and everything worked
normally. I was semi-pissed that neither Canon nor Vivitar pointed out
this problem with a 500 mm Mirror lens. My Vivitar lens now just sits on
a closet shelf, unused.
I guess it's just as well because I now use my Panasonic Lumix FZ-15
with f 2.8 Image Stabilized 36-432mm (Equiv. F.L.) lens for everything.
The camera does all the focusing and gets it spot on every time.
Bob Williams
Alfred Molon
> IIRC you're shooting Nikon, correct? I'm not aware of a Nikon zoom which
> goes to 300mm and is compatible with the Nikon TC-2EII, though I may be
> wrong. That would limit you to a 3rd party TC. Regardless of the
> manufacturer, you will also lose 2-stops with a 2x. Which will effect AF
> speed, and depending upon which body you may lose AF altogether if the max
> aperture is smaller than f/5.6.
Hmmm... in December while travelling in Malaysia I met a guy with a D700
who was using a 300mm F2.8 lens with a 2x teleconverter:
http://www.ddde.de/D700_300mm.png
Is this a fixed focus lens or a zoom?
--
Alfred Molon
------------------------
Olympus 50X0, 8080, E3X0, E4X0, E5X0, E30 and E3 forum at
http://tech.groups.yahoo.com/group/MyOlympus/
http://myolympus.org/ photo sharing site
Don Stauffer
If you use Nikon,
> look for the 500mm f8 Nikkor mirror described (it is a
> "gem"), and put up with its "bad bokeh" (which actually
> helps to make its images look sharper and more
> contrasty).
I was wondering about that. Theoretically, a lens with a central
obscuration like a Cassegrain should have an MTF peaking effect at high
spatial frequencies, at the expense of losing some shading nuances.
Don Stauffer
> On Fri, 27 Feb 2009 09:31:10 -0600, in rec.photo.digital Don Stauffer
> <stau...@usfamily.net> wrote:
>
>> My wife and I both have zooms that go out to 300mm, but occasionally
>> we'd like a longer option. I don't want to spend a lot of money, 'cause
>> we wouldn't use it that often.
>>
>> Which do folks think would have better performance- a 2X converter, or
>> one of those 600mm "mirror" lenses?
>
> goes to 300mm and is compatible with the Nikon TC-2EII, though I may be
> wrong. That would limit you to a 3rd party TC. Regardless of the
> manufacturer, you will also lose 2-stops with a 2x. Which will effect AF
> speed, and depending upon which body you may lose AF altogether if the max
> aperture is smaller than f/5.6.
My wife has a Tamron, mine is a Nikkor 70-300. Now, I have a D40X, so
the Nikkor zoom, which I bought used, does not autofocus, but I seldom
autofocus anyway. I am a reactionary, who is only now beginning to
accept auto exposure :-)
BTW, since I would certainly have a converter/300mm combo on a tripod,
and do not autofocus, I don't worry much about the loss of speed.
Don Stauffer
> In article <elniq4dm07ml421tr...@4ax.com>, m...@mine.net
>
>>> Which do folks think would have better performance- a 2X converter, or
>>> one of those 600mm "mirror" lenses?
>> IIRC you're shooting Nikon, correct? I'm not aware of a Nikon zoom which
>> goes to 300mm and is compatible with the Nikon TC-2EII,
>
>
> adapter. You get a very sharp 1500mm f/13 that will auto-expose but not
> auto-focus.
>
> Photo of my setup and some examples here:
>
> http://www.netaxs.com/~mhmyers/camera.html#FS
>
Thanks, I will look into that.
Don Stauffer
>
> What sort of shooting will you use this for?
> Birds in the back yard with a tripod?
> Hiking & traveling?
>
All of above. However, even while hiking and traveling I'd have a tripod.
Alfred Molon
> Fixed,focal length, not focus, and a very nice lens. See:
> http://www.nikonusa.com/Find-Your-Nikon/Product/Camera-Lenses/2154/AF-S-VR-NIKKOR-300mm-f%252F2.8G-IF-ED.html
Interesting. So this guy was walking around with a lens fixed at 600mm,
with no way to zoom in or out? How impractical.
David Ruether
> David Ruether wrote:
>> If you use Nikon,
>> look for the 500mm f8 Nikkor mirror described (it is a
>> "gem"), and put up with its "bad bokeh" (which actually
>> helps to make its images look sharper and more
>> contrasty).
[The one recommended is the earlier, larger version, but
with "barrel" rather than rear ring focusing - although the
more compact later Nikkor is almost as good for distance
shooting, and a tad better at closer focus distances.]
> I was wondering about that. Theoretically, a lens with a central obscuration like a Cassegrain should have an MTF peaking effect
> at high spatial frequencies, at the expense of losing some shading nuances.
From what I've seen, a very few mirrors (the Nikkor 500mm
f8s, the Minolta 250mm, and maybe the Tamron 350mm f5.6)
are good (but there may be others). I did not like any other I
tried (Vivitar Series I 600/800mm, Tamron 500mm, Nikkor
500mm f5, Nikkor 1000mm, MTO 1000mm, and likely some
others I've forgotten. The Nikkor 500 seems to have "extra DOF"
due to its high contrast, and it is *relatively* easy to focus (but
of course, atmospheric effects and camera-lens steadiness can
spoil things, even if focus is correct). Here is an example of a
"deep" subject that appears to be entirely covered by the DOF
with this mirror, at -
http://www.donferrario.com/ruether/500mm-Nikkor.htm
BTW, this is a bit of a monster, but the 100-500mm Cosina is
very impressive (but SLOW!) 100-400mm, and decent out to
500mm, and the Nikkor 300mm f4.5 ED-*non-IF* (rare, but
much better than the 300mm f4.5 ED-IF) is really excellent on
the TC300 2X converter, but neither of these is compact. The
best combination of performance, price, availability, and
portability is, I think, the Nikkor 500mm mirror described
above.
--DR
Alfred Molon
> No. He has a step zoom. 300mm or 600mm. You obviously don't shoot wildlife
> photography where at many times reach can be everything.
True, reach matters a lot in some situations.
Still, the same guy just half an hour before was shooting elephants
(Borneo pygmy elephants) at a distance of about 10m with the 300mm lens
and 2x teleconverter on. With that setup he was only able to capture
part of the head.
I was instead using a 70-300mm lens (105-450 equiv.) and got both
closeups of the elephants and the whole elephants (using focal lengths
between 150 and 450mm).
--
Alfred Molon
------------------------
Olympus 50X0, 8080, E3X0, E4X0, E5X0, E620, E30, E3 forum at
Paul Furman
That triggered my Escher meter... I guess it's just optical illusions;
he small window above and stone wall joints appear to be tilted a bit.
> BTW, this is a bit of a monster, but the 100-500mm Cosina is
> very impressive (but SLOW!) 100-400mm, and decent out to
> 500mm, and the Nikkor 300mm f4.5 ED-*non-IF* (rare, but
> much better than the 300mm f4.5 ED-IF) is really excellent on
> the TC300 2X converter, but neither of these is compact. The
> best combination of performance, price, availability, and
> portability is, I think, the Nikkor 500mm mirror described
> above.
I have a monster sized old 500mm f/4.5 by Century, a Hollywood
manufacturer in the early 80's. I'm going to get rid of it though since
I discovered my 300mm f/2.8 (old MF 3rd party lens) with a 1.4x
teleconverter is sharper, smaller & faster. The 300 plus TC cost more
though. The 500/4.5 was $500 with a 17-pound tripod. It was used for
shooting surfers so not exactly like-new condition.
Paul Furman
> trevor thomas [the P&S troll] wrote:
>> Bob Williams wrote:
>>> Don Stauffer wrote:
>>
>>>> My wife and I both have zooms that go out to 300mm, but occasionally
>>>> we'd like a longer option. I don't want to spend a lot of money,
>>>> 'cause we wouldn't use it that often.
>>>>
>>>> Which do folks think would have better performance- a 2X converter,
>>>> or one of those 600mm "mirror" lenses?
>>>>
>>>> Does anyone know what optical configuration those mirror lenses are-
>>>> are they Cassegrains, or Newtonians (flat folding lens), or
>>>> something entirely different?
>>>
>>> Don, I bought a 500mm, f8.0 Vivitar Mirror lens for my Canon A-1 film
>>> camera and was very disappointed in the results.
>>> Mirror lenses have only one f-stop (f8.0 in this case).
>>> At f8.0 it is VERY difficult to focus accurately even in bright sunlite.
>>> At low light levels it was almost impossible to focus accurately.
>>> My canon A-1 has a split image focusing aid. At f8.0, one side of the
>>> aid tends to go black as you try to focus.
There have been improvements in the 3rd party replacement screens, they
black out much slower. The limitation becomes the overall dark screen in
anything less that bright daylight.
http://www.katzeyeoptics.com/page--Katz-Eye-Plus--plus.html
>> That's not caused by the size of the aperture but the focal-length of the
>> lens and the angle of the light-rays hitting the focusing screen.
>>
>> As example, special focusing screens for the Olympus line of SLR cameras
>> were designed with specific optical applications in mind. I particularly
>> like my 100% clear one with the shorter focal-length fresnel lens for
>> microscopy and astrophotography purposes. It provides for an ultra-bright
>> display with little to no light loss for those applications,
>> independent of
>> whatever focal-length is providing the image.
That would show a lot more DOF than the final photo.
http://brashear.phys.appstate.edu/lhawkins/photo/om-screens.shtml
"Focus by microprism only. Clear screen does not show good or bad focus."
I would not assume that coming from the P&S troll.
> but before I got the mirror lens, I used
> a 400 mm f4.5 tele lens (refractor) and never had any kind of focusing
> problem with it. Focusing was done "Wide Open" and everything worked
> normally. I was semi-pissed that neither Canon nor Vivitar pointed out
> this problem with a 500 mm Mirror lens. My Vivitar lens now just sits on
> a closet shelf, unused.
>
> I guess it's just as well because I now use my Panasonic Lumix FZ-15
> with f 2.8 Image Stabilized 36-432mm (Equiv. F.L.) lens for everything.
> The camera does all the focusing and gets it spot on every time.
You lose high ISO performance though. It's worth noting that 300mm on a
DX SLR is 450mm equivalent, so the OP is already there with his current
lens.
Paul Furman
> In article me@mine, says...
>
>> No. He has a step zoom. 300mm or 600mm. You obviously don't shoot wildlife
>> photography where at many times reach can be everything.
>
> True, reach matters a lot in some situations.
>
> Still, the same guy just half an hour before was shooting elephants
> (Borneo pygmy elephants) at a distance of about 10m with the 300mm lens
> and 2x teleconverter on. With that setup he was only able to capture
> part of the head.
> I was instead using a 70-300mm lens (105-450 equiv.) and got both
> closeups of the elephants and the whole elephants (using focal lengths
> between 150 and 450mm).
I'll bet his pictures came out nice though <g>.
300/2.8 is a very useful lens and doesn't need to be so large. My old
manual focus Tokina, similar to the Nikkors of the day is manageable
with the hood removed and costs 1/10th of the new VR version. The 1.4x
TC is surprisingly small. Some of the old Nikkors have a built in
retractable hood.
Grimly Curmudgeon
drugs began to take hold. I remember "Marcin"
<yahoo2n@delete@poczta.onet.pl> saying something like:
>Maybe try to find Lens made by Koreanian company Samyang.
>
>Samyang 500mm MC f/5,6 - about 100 EUR !!! (nikon, canon, sony, pentax)
>
>Samyang 650-1300mm IF MC f/8,0-16,0 Canon - about 150 EUR !!!!!!
>
>I don't have information about quality of that product because is brand new
>on the Polish market.
Franky, I doubt it will be any better than a Centon, of similar value.
David Ruether
"Paul Furman" <paul-@-edgehill.net> wrote in message news:mICql.21422$Ws1....@nlpi064.nbdc.sbc.com...
> David Ruether wrote:
>> Here is an example of a
>> "deep" subject that appears to be entirely covered by the DOF
>> with this mirror, at -
>> http://www.donferrario.com/ruether/500mm-Nikkor.htm
> That triggered my Escher meter... I guess it's just optical illusions; the small window above and stone wall joints appear to be
> tilted a bit.
> --
> Paul Furman
Relative to each other? It does appear that I have the
window sides not quite vertical relative to the frame
edges, and some of the vertical stone mortar joints
lean a bit more the same way, but I suspect the latter
is due to the sun angle across stones with noticeable
depth (they are not flat) - maybe...;-) Or, is it the little
window at the top that doesn't appear to be in the
same plane? Dunno on that one. It has a frame that
makes some of its visible vertical lenght appear to be
tilting - maybe...;-) But, for 500mm at not an enormous
distance, look at all that DOF, going from the shingles
w-a-y back in the upper left all the way forward to the
right edge of the visible stone wall - and no tilts/swings
were needed and no stopping down was possible...;-)
--DR
Chris Malcolm
> In article <70rl1rF...@mid.individual.net>, Chris Malcolm says...
>> Except for those which autofocus, like the Minolta/Sonys.
> Which ones specifically?
AFAIK all of them, but I'm not an expert.
--
Chris Malcolm
Toby
There are different tradeoffs. I have an 80-200 f2.8 Nikon lens and a Tokina
100-300 f4, and use them with a Nikon 2x converter. So the glass is
relatively good. I find a great loss of sharpness using the Tokina at 300
with the teleconverter (shorter focal lengths are better). The Nikon at 200
retains better sharpness, but is plagued with chromatic aberration and some
spherical aberration. In both cases it there is a significant magnification
of inherent faults in those lenses, which are observable without the
extender, but really become significant with the extender.
The mirror lenses I have used are not as globally sharp or contrasty as a
normal lens, but are well corrected and consistent across the frame. The
fixed aperture is not a large limitation anymore with electronically
controlled shutters running on aperture priority, and the lack of contrast
is easily correctable in any decent image-editing program. If you don't mind
the bokeh (I like it too) a decent mirror is a good choice, though they
usually suffer from a very limited close-focusing distance.
I have a 150-500 f5.6 Tokina ATX manual lens made about 20 years ago. They
are still around on the used market and sometimes can be had quite cheaply.
This turns out to be an excellent value. They are quite sharp and well
corrected. In my own tests it performs as well as my Nikkor 400ED 5.6
(actually sharper in the center, but slightly less sharp at the corners of
the frame). In addition the performance with a 2x extender is acceptable:
better than a 1000mm f11 mirror that I have. It is huge and heavy, but well
worth looking for if it works for you.
Toby
"Don Stauffer" <stau...@usfamily.net> schrieb im Newsbeitrag
news:49a80743$0$87068$815e...@news.qwest.net...
Bob Williams
That is an interesting article.
Kind of shoots down Trevor's thesis doesn't it?
Wish I had the Katz-Eye 6 years ago when I bought the mirror lens.
But now, my prized Canon A-1 Film Camera is a modern anachronism.
That is true.
However, for me, that is not a serious problem.
I do most of my work outdoors and f 2.8 (even at 432mm!!)is a big help.
Indoor shots is where I wished the Panny had better high ISO
performance. Flash, of course, often helps but there is nothing like
ambient light for capturing the true "mood" of the moment.
But Hey! You have to accept trade offs somewhere.
Bob Wiliams
trevor thomas
wrote:
>Paul Furman wrote:
No. It supports it 100%, if you can ever comprehend what you were reading.
But then you should only discuss things that you know about. Clearly,
optics and cameras are not in that category for you.
But then someone like you would always trust some misinformation marketing
hype from a company trying to sell their 3rd-party patch to attempt to
ameliorate an originally bad camera design.
It is the angle of the light-cone that is entering the micro-prism
focus-assist area. This is due to the focal-length of the lens in use. The
narrower that you make that light-cone (by stopping down) only exacerbates
the original problem caused by the various focal-length lenses used with
those screens. Read the "notes" section on the Olympus page link.
>Wish I had the Katz-Eye 6 years ago when I bought the mirror lens.
>But now, my prized Canon A-1 Film Camera is a modern anachronism.
>
>>>> That's not caused by the size of the aperture but the focal-length of
>>>> the
>>>> lens and the angle of the light-rays hitting the focusing screen.
>>>>
>>>> As example, special focusing screens for the Olympus line of SLR cameras
>>>> were designed with specific optical applications in mind. I particularly
>>>> like my 100% clear one with the shorter focal-length fresnel lens for
>>>> microscopy and astrophotography purposes. It provides for an
>>>> ultra-bright
>>>> display with little to no light loss for those applications,
>>>> independent of
>>>> whatever focal-length is providing the image.
>>
>> That would show a lot more DOF than the final photo.
If you had any real photography experience, more than reading newsgroups
and webpages or taking snapshots of your cats with your disposable cameras
you'd know that the focusing screen mentioned is not used for that purpose.
>> http://brashear.phys.appstate.edu/lhawkins/photo/om-screens.shtml
>> "Focus by microprism only. Clear screen does not show good or bad focus."
There is no microprism on the focusing screen to which I referred, it isn't
even listed on that page. Quite a few companies produced alternate focusing
screens for the Olympus line of cameras. Focusing on my favorite screen is
not done by microprism, but then you'd have to have some knowledge and
experience with cameras to know how to use it properly for focusing. I'll
leave the explanation of the method used on clear focusing screens as one
of your many net-knowledge-only google-photographer exercises.
Go involve yourself in newsgroups where you might have some experience.
Might I suggest the alt.games.rpg hierarchy where people like you excel at
their imaginary lives.