Schneider-itis: The Perennial Problem

[Bernice Loui]

Trying to compare the slightly degraded edge coating 210mm SSXL to another lens of similar focal length is NOT a valid comparison for a very long list of factors, from different lens formula/design, focal length, lighting conditions and how this impacts the film image, reflectance from film, variations in lens coatings, stray light inside the bellows caused by over sized image circle and much more.

~The Only Valid comparison test is absolute identical image making conditions with the lens "perfect" then under absolutely identical conditions with the same lens edge coating degraded.~

As for the flocked -vs- non flocked as delivered projector lens example, this is typical of a lower quality projector lens. Projection lenses same as other optics comes in a variety of abilities and designs goals. Consider the Schneider Cinelux


or ISCO Ultra Star projection lenses


The stray light causing contrast reduction is very similar to stray light inside the camera bellows from a lens with far excessive image circle for the needs of the film image area.

Attraction of these projection lenses is much about their large aperture, out of focus rendition and into out of focus rendition, which has become a 'thing" of fashion these days with sheet film. This image style trend appears to be a carry over from 35mm and digital image styles where large full aperture lenses are often used in this image making style. Yet, this image making style has been around long ago, common in cinema folks and sheet film folks from decades ago. Then came the group f64 "everything in the image must be in sharp focus" image style.. which pushed out the how out of focus and into out of focus rendition image making style. This appears to be why the absurd market value for large full aperture sheet film lenses like the Schneider 150mm f2.8 Xenotar and others.

This brings up the topic of barrel lenses and older shutters with a nice round iris -vs- modern shutters like Copal/Compur/Prontor/ Sinar DB/DBM mount and others with less than round iris due to the lesser need to be concerned with out of focus and into out of focus rendition due to the influence of Group f64 on sheet film images. Projector lenses tend to have no iris and large apertures with an image circle that can be large enough for various film or digital imager format.




Bernice

I'll do what I can before sending the lens off next month.
It would be difficult to get the exact same conditions, but I'll make notes.

Here's a different lens with a slightly different issue, but worth noting.
This is a projector lens I have. The inside was not black, it was more of a dull dark gray.
I blackened the inside, and the differences are immediately apparent.
I'm starting to see the same effect on the 210, though it's very minor compared to the projector lens problem shown below.