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Petzval Paul
6-Feb-2012, 21:01
Hi everyone,

I was the nut who recently won the 11" P&S S.A. that was auctioned off recently. Although I have had a P&S Synthetic for some years, I have never used a semi achromatic lens and am curious how to focus it. The Synthetic is a breeze to use and has an awesome glow, more even than the S.A. based on a quick comparison, and I have even used non-achromatic lenses. With a semi achromatic lens, what is the focusing adjustment and how is using one different from using one that is fully uncorrected for chromatic aberrations?

Garrett recently posted some pics shot with a Stuss Pictorial Lens using both film and wet plate. There seems to be a different kind of diffusion using the wet plate emulsion. Does anybody have any specific knowledge of how the orthochromatic nature of an emulsion effects the image using a non, or semi, chromatically corrected lens? Indeed, the particular look of just such lens is why I had been searching for so long for the Smith lens.

Jim Galli
6-Feb-2012, 21:22
Hi everyone,

I was the nut who recently won the 11" P&S S.A. that was auctioned off recently. Although I have had a P&S Synthetic for some years, I have never used a semi achromatic lens and am curious how to focus it. The Synthetic is a breeze to use and has an awesome glow, more even than the S.A. based on a quick comparison, and I have even used non-achromatic lenses. With a semi achromatic lens, what is the focusing adjustment and how is using one different from using one that is fully uncorrected for chromatic aberrations?

Garrett recently posted some pics shot with a Stuss Pictorial Lens using both film and wet plate. There seems to be a different kind of diffusion using the wet plate emulsion. Does anybody have any specific knowledge of how the orthochromatic nature of an emulsion effects the image using a non, or semi, chromatically corrected lens? Indeed, the particular look of just such lens is why I had been searching for so long for the Smith lens.

I don't use any fancy math with modern panchromatic film. Roll through the focus and when you come back in, err on the side of focused too near.

goamules
7-Feb-2012, 07:08
Hey Paul, congratulations! Like Jim says, the modern film compensates a lot for any complications focusing. And with regular film I do as he says, and what you see is what you get. But as you mention, I've seen when I am using a media with a narrow bandwidth, like wetplate or something like the old emulsions, you will get more softness due to chromatic color shift.

If you are going to shoot more orthochromatic media, you may want to read through some of the period literature, like The Photo Miniature, Mar 1921, Vol XVI, No. 181:

A series of experiments was made (using
the camera as a lens-testing bench) with a 12-inch
Struss lens, focused on a window curtain of rather
coarse fabric. The lens was stopped down to F:11 to
avoid spherical aberration, and three exposures were
made on Standard Orthonon plates. The first was
focused as sharply as possible with a magnifier; the
second was made with the same camera extension, but
with a K2 filter before the lens and proportionately
lengthened exposure; the third was made after racking
the lens in 1/40, of an inch, as recommended. The plate
exposed through the filter gave the sharpest negative
of the three in definition, and would pass as one made
with a rectilinear lens, the threads of the curtain fabric
being clearly and sharply defined. In the other two
exposures, while the one made at the visual focus has
the greater amount of apparent halo, the curtain
texture is approximately the same.
For practical pictorial use, therefore, the conclusion
is that chromatic aberration, while it affects the result,
can be controlled only in one way by the photographer,
namely, photographing by monochromatic light (as
in using an orthochromatic plate with a K2 filter,
virtually light of one wave length), the softness resulting
from this aberration affecting all parts of the
image equally.

Petzval Paul
9-Feb-2012, 05:11
Thanks Garrett. That is a big help. Pretty much just what I needed :)