Are there optical disadvantages to large-coverage lenses?greenspun.com : LUSENET : Large format photography : One Thread
I'm wondering about whether there are downsides (besides weight and cost, of course!) to using extra-large coverage lenses in cases where you don't need the coverage.
Consider some 90mm options for 4x5 cameras from only two companies. Schneider's standard SuperAngulon 90 has pretty good coverage (216mm? I don't have spec sheet, so these numbers are from memory) and the front element is fairly small (67mm filter size). Nikon offers two 90mm's, both with image circles of 236?mm; the f/8 has a 67mm front element, I believe, and the f4.5 has an 82mm front element. Finally, Schneider's 90XL has excellent coverage (259mm?) but the front element is a huge 95mm filter size.
My question is whether having a larger front element and more coverage will "catch" glare/flare and lights/sun that are out of the portion of the image being recorded on film. In other words, all else being equal, is it optically more prudent to only buy as little coverage as you think you can get away with, or is no harm done (again, notwithstanding weight and cost) by investing in that might-need-it-someday huge image circle? Thanks in advance...
-- Bill Daily (WRDaily@aol.com), February 09, 1998
Some time ago, while looking at a lens in the 120mm range, I was advised by one of Calumet's large format specialists that a true wide angle design (Super Angulon or Nikkor SW) would probably perform less well at close distances than a lens of equivalent focal length with less coverage (e.g., Super-Symmar HM). Ultimately, I decided to go for the true wide angle, but its something to consider if you will be using the lens this way.
-- Rob Rothman (email@example.com), February 10, 1998.
Go for the coverage. I have the Schneider 90/5.6 Super Angulon which has an image circle of 235mm and a front element of 82mm. I also have Nikon's 120/8 SW (image circle of 312mm and 77mm filter thread). Both these lenses are quite large but I have had no problem with flare and both are extremely sharp. The larger image circles come in real handy when using rise and extreme tilt which, if you are doing landscape work, you will use. Unless you have alot of experience doing the type of photography you are doing now and are sure you can get by with the smaller image circles go with the ones which will give you the greatest flexibility in the long run.
-- Mark Windom (firstname.lastname@example.org), February 10, 1998.
The concern here is legitamite concern. If the coverage is too large then light hiting the inside of your bellows will reflect back and give you reduced contrast on the film. If your camera has a large (wide) bellows this is less of a problem and if the bellows is a raly good matt black this is olso less of a problem
-- Laurence Cuffe (Laurence.email@example.com), February 14, 2001.
The flare effect is more visible with longer lenses, and is the result of stray light bouncing on the bellows and reducing the contrast of the image on film. Cameras with narrow bellows (some flatbeds or field) are more sensible to that effect than cameras with an ample bellows (monorail type). But this effect can be prevented by using a lens shade or compendium. Glare is the effect of light reflecting on glass-air surfaces inside the lens. Most modern multicoated lenses will not easily demonstrate that effect. But yes, lenses with huge image circle may require more cares to shade them from stray light than other lenses. As for what difference it will make between a Super-Angulon and a Super-Angulon XL, I think the real problems are the size and the cost of the lens and filters, and not so much the ill effects of the larger image circle. If you need the extra coverage, go for it. Otherwise, you will be satisfied with the standard version.
-- Paul Schilliger (firstname.lastname@example.org), February 14, 2001.