Caltar lens sharpness

You are probably right, and I apologize for any wasted time in this
listserve.

jjs wrote:
If I were in your situation, I would carefully reconsider the setup
for the
picture. It seems to me to be purely operator error.

Sorry to labor the subject, but when I bought the Caltar, the shop
owner told me that it was made by Horseman (a Japanese company). Not
that I care, but am just curious.

It seems that most of the really good lens designs came out of Germany
before World War II.

I don't want to start a new thread on this topic because I don't have
time to follow it, but it is interesting to learn about some of the
history now that I am becoming and old fart.

Many thanks!

Bob G wrote:
The 90mm HR Caltar is a fine Rodenstock lens and should be extremely
sharp. It's not at its best at near distances, but it should still be
quite good.
Shorter focal length lenses should generally not be stopped down all
the way, since diffraction is a problem. The Caltar should be best at
f11 or f16.

See that both lens cells are screwed on all the way. Check for thread
damage. If all's OK, then remove the cells and rattle them carefully,
listen for any loose elelements.

Some shutters come with "anchoring" studs - if not removed or
allowance
made for insertion into a hole on the lensboard, your whole assembly
might be out of alignment.

Are you using a Fresnel lens? If inserted on the wrong side it may be
causing a focus shift - that would be even more noticeable with your
180mm Schneider, although you're shooting way stopped down with it
and
your DOF might be compensating for softness.

Sorry to labor the subject, but when I bought the Caltar, the shop
owner told me that it was made by Horseman (a Japanese company). Not
that I care, but am just curious.

It seems that most of the really good lens designs came out of Germany
before World War II.

I don't want to start a new thread on this topic because I don't have
time to follow it, but it is interesting to learn about some of the
history now that I am becoming and old fart.

Many thanks!

Bob G wrote:
The 90mm HR Caltar is a fine Rodenstock lens and should be extremely
sharp. It's not at its best at near distances, but it should still be
quite good.
Shorter focal length lenses should generally not be stopped down all
the way, since diffraction is a problem. The Caltar should be best at
f11 or f16.

See that both lens cells are screwed on all the way. Check for thread
damage. If all's OK, then remove the cells and rattle them carefully,
listen for any loose elelements.

Some shutters come with "anchoring" studs - if not removed or
allowance
made for insertion into a hole on the lensboard, your whole assembly
might be out of alignment.

Are you using a Fresnel lens? If inserted on the wrong side it may be
causing a focus shift - that would be even more noticeable with your
180mm Schneider, although you're shooting way stopped down with it
and
your DOF might be compensating for softness.

I don't know whose time is being wasted since no one is forced to
read stuff here. f/64 can be useful for extending depth of field but
diffraction blur begins to be significant. At f/90 diffraction blur is
considerable even on 8x10.
Some have suggested misaligned cells or elements. The cells should
be screwed in all the way. Not forced, just hand tight. The cell
spacing of some lenses can be rather critical but it tends to affect
corner sharpness more then the center. Most lens mounts are such that
the elements are automatically centered and spaced. A few modern lenses
have thin shims used to optimise the lens during assembly. These are
virtually never found on lenses made before around 1970. Occasionally,
an element may be revrsed but that usually causes a gross blurring of
the image, not anything subtle.
As far as depth of field, it is a problem with large format because
small stops are needed to get it and diffraction blur may be come a
problem. To some degree tilting the lens or back may help because the
field of focus can then be tilted to match a tilted subject. If you can
do this a much larger stop can be used and a sharper image produced.
There can also be problems with a mismatch between the ground glass
and the film plane. If the ground glass image is sharp under a strong
magnifier but the film is blurred the film plane is probably wrong.
This can be due to a misaligned ground glass, especially where a field
lens (fresnel) is used, or it can come from bad film holders. One can
examine the aerial image from the lens using a high quality magnifier.
This will look sharper than the ground glass image because it is not
being diffused by the ground glass. The aerial image will give some
idea of what the lens is actually doing.
Focus plane problems can be detected by photographing a tilted
subject at a large lens opening to minimise the depth of field. Use
something like a yardstick with an indicator on it at the point you
have focused on. The film should show best focus at this point. If not
the film is not where the ground glass was.
If you find you are having focus plane problems write back and I will
make some suggestions about how to track down the source.

--
Richard Knoppow

I don't know whose time is being wasted since no one is forced to
read stuff here. f/64 can be useful for extending depth of field but
diffraction blur begins to be significant. At f/90 diffraction blur is
considerable even on 8x10.
Some have suggested misaligned cells or elements. The cells should
be screwed in all the way. Not forced, just hand tight. The cell
spacing of some lenses can be rather critical but it tends to affect
corner sharpness more then the center. Most lens mounts are such that
the elements are automatically centered and spaced. A few modern lenses
have thin shims used to optimise the lens during assembly. These are
virtually never found on lenses made before around 1970. Occasionally,
an element may be revrsed but that usually causes a gross blurring of
the image, not anything subtle.
As far as depth of field, it is a problem with large format because
small stops are needed to get it and diffraction blur may be come a
problem. To some degree tilting the lens or back may help because the
field of focus can then be tilted to match a tilted subject. If you can
do this a much larger stop can be used and a sharper image produced.
There can also be problems with a mismatch between the ground glass
and the film plane. If the ground glass image is sharp under a strong
magnifier but the film is blurred the film plane is probably wrong.
This can be due to a misaligned ground glass, especially where a field
lens (fresnel) is used, or it can come from bad film holders. One can
examine the aerial image from the lens using a high quality magnifier.
This will look sharper than the ground glass image because it is not
being diffused by the ground glass. The aerial image will give some
idea of what the lens is actually doing.
Focus plane problems can be detected by photographing a tilted
subject at a large lens opening to minimise the depth of field. Use
something like a yardstick with an indicator on it at the point you
have focused on. The film should show best focus at this point. If not
the film is not where the ground glass was.
If you find you are having focus plane problems write back and I will
make some suggestions about how to track down the source.

--
Richard Knoppow

wrote in message
oups.com...
You are probably right, and I apologize for any wasted time in this
listserve.

jjs wrote:
If I were in your situation, I would carefully reconsider the setup
for the
picture. It seems to me to be purely operator error.

You did not waste any time or resources, Sir. I am sure your experience
applies to many of us. What I was trying to suggest to the collective was
that when a good lens performs very poorly often it is the setup at fault.

wrote in message
oups.com...
You are probably right, and I apologize for any wasted time in this
listserve.

jjs wrote:
If I were in your situation, I would carefully reconsider the setup
for the
picture. It seems to me to be purely operator error.

You did not waste any time or resources, Sir. I am sure your experience
applies to many of us. What I was trying to suggest to the collective was
that when a good lens performs very poorly often it is the setup at fault.

wrote in message
oups.com...
Sorry to labor the subject, but when I bought the Caltar, the shop
owner told me that it was made by Horseman (a Japanese company). Not
that I care, but am just curious.

It seems that most of the really good lens designs came out of Germany
before World War II.
[...]

We are fortunate to have at least two lens experts in this group. Perhaps
they will respond. Let me add my impressionistic view, which is probably
common, and let the historians correct me.

Almost everything that had to be known about lenses for film was known
before 1950. The technology to make the lenses was expensive, and in some
cases nonexistent (for example to make aspherics and proper coatings) Only
a robust economy with well informed engineers could make affordable, very
high-quality lenses. Zeiss managed to pull it all together so that they
could make the quantity-with-quality necessary to maintain the business.
Less impressive marketing and engineering enterprises did not do well. (Not
all Zeiss lenses were excellent - but such things occur in an early
enterprise.)

Again, perhaps someone can correct me on this point. Example: the Biogon
design was known very early. After the second generation Biogon there was
not much at all that could be done to improve the optics ('cept coatings).
The Biogon and all the other lenses were designed by a brilliant engineer
who would conceive of an optical formula (design, and materials) then to
prove the design they would perform, or direct savants to do, manual
ray-tracing - a hugely daunting task that could take months. When computers
finally became affordable (around the time of the DEC PDP), then companies
could do ray-tracing in a fraction of the time (but still many hours) and it
was found that the Biogon could not be significantly improved! Is that not
true?

TIA
---
jjs - another Olde Pharte

wrote in message
oups.com...
Sorry to labor the subject, but when I bought the Caltar, the shop
owner told me that it was made by Horseman (a Japanese company). Not
that I care, but am just curious.

It seems that most of the really good lens designs came out of Germany
before World War II.
[...]

We are fortunate to have at least two lens experts in this group. Perhaps
they will respond. Let me add my impressionistic view, which is probably
common, and let the historians correct me.

Almost everything that had to be known about lenses for film was known
before 1950. The technology to make the lenses was expensive, and in some
cases nonexistent (for example to make aspherics and proper coatings) Only
a robust economy with well informed engineers could make affordable, very
high-quality lenses. Zeiss managed to pull it all together so that they
could make the quantity-with-quality necessary to maintain the business.
Less impressive marketing and engineering enterprises did not do well. (Not
all Zeiss lenses were excellent - but such things occur in an early
enterprise.)

Again, perhaps someone can correct me on this point. Example: the Biogon
design was known very early. After the second generation Biogon there was
not much at all that could be done to improve the optics ('cept coatings).
The Biogon and all the other lenses were designed by a brilliant engineer
who would conceive of an optical formula (design, and materials) then to
prove the design they would perform, or direct savants to do, manual
ray-tracing - a hugely daunting task that could take months. When computers
finally became affordable (around the time of the DEC PDP), then companies
could do ray-tracing in a fraction of the time (but still many hours) and it
was found that the Biogon could not be significantly improved! Is that not
true?

TIA
---
jjs - another Olde Pharte

In article .com,
wrote:
Sorry to labor the subject, but when I bought the Caltar, the shop
owner told me that it was made by Horseman (a Japanese company). Not
that I care, but am just curious.

I think that might be right. For some time there was a single wide
angle lens in the Caltar lineup that was not made by Rodenstock,
unlike everything else they sold at the time. I *think* it was the
90mm, but I'm not sure.

Still should be quite a good lens, though. I have to agree that a
likely cause of this problem is that something in your camera is
not square, but the very small apertures you are using with the
Symmar (the advice you got from the Kodak brochure was really meant
for _single elements_ of convertible lenses) are hiding the alignment
problem. Compare the two lenses at f/16 and see what you get; it may
be that neither gives you a sharp image and that would indicate an
alignment problem with your camera.

--
Thor Lancelot Simon

"The inconsistency is startling, though admittedly, if consistency is to be
abandoned or transcended, there is no problem." - Noam Chomsky