Checking for vignetting. Aperture ?greenspun.com : LUSENET : Large format photography : One Thread
I check for vignetting due to the lens hood (or a filter holder) by looking through the cut corners of the ground glass. I look to see if I see the hood. Should that be done with the lens wide often (what I currently do to be conservative) or stopped down to the taking aperture ? Thanks.
-- Quang-Tuan Luong (firstname.lastname@example.org), May 05, 2000
Wide open, in my opinion.
-- Ellis Vener (email@example.com), May 05, 2000.
My vote would be for viewing at the taking aperture. It stands to reason that since light can turn around corners, if the entire taking aperture is visible through the cut corners, then all exiting rays will reach the corners of the film.
-- Robert A. Zeichner (firstname.lastname@example.org), May 05, 2000.
This should be the last step you take before you cock and trip the shutter. Through the corner cut-out of the groundglass look at your wide open lens-the aperture will look somewhat like a cat's eye pupil. Now slowly stop down until your the lens opening shape changes into a round (human pupil shape) opening. This is the largest stop at which you will have no vignetting. Check top and bottom is you used rise/drop or front/back swing; check left and right if you used L/R shift or swing.
-- Hans Berkhout (email@example.com), May 06, 2000.
first I would say that when you check the circle you have to see a full circle. So if you see a full circle wide open it mean that it is good for allthe other aperture. if you don't see a fulll circle (or if you see cat's eye as we say in france) stop down till you see it and this is the aperture without vignetting
-- nze christian (firstname.lastname@example.org), May 07, 2000.
"A few points bear repeating and emphasizing. First, beweare of vignetting! It can be hard to see on the ground glass because it may appear only when the lens is stopped down . . . . " Ansel Adams, "The Camera," p. 159. It would seem from this that Ansel is telling us to check for vingetting with the lens stopped down to the taking aperture.
-- Brian Ellis (email@example.com), May 08, 2000.
There is no doubt that when checking for the vignetting caused by the lens barrel (ie the limit of coverage of the lens), one needs to stop down. Logic would have that this applies also to vignetting caused by other accessories, but I had often hearg that for this second kind of vignetting, you do it wide open, hence the confusion, and the question.
-- Quang-Tuan Luong (firstname.lastname@example.org), May 08, 2000.
Having many years ago conducted on-film tests which confirmed Adams' claim, I can report that one must perform the vignetting check at taking aperture, *not* wide open.
-- Sal Santamaura (email@example.com), May 25, 2000.