Massive image circle on small format, any problems with out lens shade?greenspun.com : LUSENET : Large format photography : One Thread
When shooting very large image circle lenses, like the Fuji 600 C, image circle = 620mm, on a very small format, 6x7 roll film back, what is the consequences of having 80% of the image circle not being absorbed on the film. Some people say the remaining light just gets absorbed by the inside of the bellows.. however, I am sure that not not 100% of the light is being absorbed, so the remaining light must go somewhere? Any one have experience at seeing the actual effects of this before and after... i.e. not blocking out most of the excess light with a lens hood? Does it lower contrast? Does it cause slight overexposures? Any input would be helpful...
-- Bill Glickman (email@example.com), December 13, 1999
I've used 8x10 lenses--a 305mm G-Claron and a 450mm Fuji-- on a 4x5 with a 6x9 roll film back with color transparency film (sorry, I have not used the 600 C). As you know, these lenses have huge coverages for the 6x9 format.
I did not notice any difference in either contrast or exposure with these lenses, compared to other 4x5 lenses of more modest coverage, either with or without a hood, in the various frames taken on the same roll of film.
That's just from my own experience. I cannot explain where the rest of the light goes. This question has been asked several times, but no satisfactory answers/explanations seem to have been provided. I wish I could give you a more technical or scientific response.
Good luck, Sergio.
-- Sergio Ortega (firstname.lastname@example.org), December 14, 1999.
The answer will depend heavily on the internal design of the camera. It should be matt black, with no surfaces that the light can glance off towards the film (matt black paint can actually be quite shiny when viewed at certain angles). In theory, all the light will be absorbed. In practice, you can get almost any effect, from slight overall contrast reduction, to massive hotspots, to nothing at all, depending on the camera and lens.
If in doubt, use a hood.
-- Alan Gibson (Alan.Gibson@technologist.com), December 14, 1999.
Flare = reduction in contrast (reduction in MTF). How much? That will depend on your system and shooting conditions, but with my system (Linhof and Wista), practically, it is observable, especially with large image cirle lenses. Before I started to using a hood, I was naive to think that I could pump 80% of non-imaging light into my bellows and get away with it. After much experimentation I no longer think so. Your situation may be different.
-- Pat Raymore (email@example.com), December 14, 1999.