loss of contrast due to light not fully obsorbed by bellowsgreenspun.com : LUSENET : Large format photography : One Thread
I have a super speed graphic with a Super Symmar XL 110. The image circle on this lense is huge. The part of the image that falls onto the inner surface of the bellows is not totaly absorbed. The light emitted off of the bellows brightens the film overall and reduces contrast. How big of an effect is this? Should I worry? What can I do about it?
-- Jon Miller (firstname.lastname@example.org), May 09, 2000
Jon, thats a very good question, I have wondered the same quite often, specially with my 600mm Fuji C with a 620mm image circle!! This question has been raised before on this forum and has had mixed answers.
Try this experiment to find out for yourself, install a lens hood and extend it outwards to cut out all the light that is not hitting the gg/film. You should focus and shoot with the apt. set at f11, focus at infintiy. Keep moving the lens hood outward until you can see the vignetting on the gg. Leave the hood there and take the shot... now you know for sure that all the light entering the lens is hitting ONLY the film, nothing else! Don't be afraid to leave the vignetting marks all around the gg so you can be sure! Then remove the lens hood and take another shot keeping everything else the same. Compare the chromes and report back. I have done this a few times myself, but my results were somewhat inconclusive... maybe you will have better luck. Shoot in bright sun to make the effects more noticeable. I think you are on to something......
If you do not have a lens hood, you can use some black material wrapped around the lens so it extends outward like a cylinder. It has the same effect as a lens hood, just not as eloquent. Also, shooting a high contrast subject is also helpful to analyze the results.
There is many of us on this Forum who also love and use the 110 XL who would be very very interested in learning the results of your test! Good luck Jon......
-- Bill Glickman (email@example.com), May 09, 2000.