Bellows flare

[ronald lamarsh]

Ok guys and gals i just finnished rereading Gordon Hutchings "The Book OF Pyro" and came across the section on bellows flare that I never paid much attention to on the first read. After reading it carefully and then thinking back in time about some of my more disappointing negatives(taken in very bright conditions late summer wheat in full sun) I was using a compendium bellows streched to the limit with the sun at my back, I have checked my bellows often and although I have never found any leaks I still tend to wrap the camera with my dark cloth. The neg seems to possess an overall fog but it doesn't appear at the edges where the film holder masks the film so I have ruled out developement, and leaks the only thing left is bellows flare, it appears to be overexposed by at least 1 stop. Any thoughts?

[Paul Schilliger]

Ronald, you could be dead on. Stretched bellows are a factor of fogging. In fact if you look inside the back of the camera, you will notice that most bellows reflect some light when they are stretched. The pleats do normally take care of the stray light.

Consider:

1) The size of the bellows. Larger bellows (most studio cameras) are safer than smaller bellows such as on folding cameras.

2) The bright lights outside the actual image but within the image circle of the lens (sky, sun, studio lighting). A tightly fitted compendium can take care of that.

3) The bellows stretching. There should always be some pleats left to intercept stray light.

[David A. Goldfarb]

Could be bellows fog, but bellows fog is usually stronger near the edges rather than an overall effect.

With the compendium shade at maximum extension, you still might not have enough to restrict the image circle adequately. This will happen if you have a lens with a very large image circle or with very short subject distances. In such cases it helps to have a mask on the front of the shade to reduce the image circle even more, to just short of vignetting.

[ronald lamarsh]

Thank you all for the insights this image in particular was with a 250mm lens in a 6x12 format in a cambo monorail so the bellows were out quite a ways, i also suspect the lens justa bit as it had quite a few imperfections that were blatantly obvious when held up to a bright light. I say had as it along with some other stuff has disappeared in favor of a 240mm g-claron. thanks again

[Armin Seeholzer]

Sorry but I only believ on bellows flare if you worked in very bright sunlight and with an f stop around 5.6 - 11 because if you luck in to a camera stoped down to f 16 of even smaller there isn't much light wich can make fogging, what I think is you used an older lens uncoated or only single coated with the sun in the picture or just a bit aoutside of it, thad gives your effect!
Just look on your groundglass at f 16 0r 22 and it is quite dim to dim to bounce around in my opinion!

Good luck and MC lenses for critical applications!