Light fall off on newer style WA lensesgreenspun.com : LUSENET : Large format photography : One Thread
Is there any brand of perhaps the newer style lenses that do not need a center filter to compensate for light fall off? I am considering a 55mm or 58mm xl and a 75mm Grandagon.On Rodenstock lenses what does the "N" on the barrel stand for?
-- Mike Kuszek (firstname.lastname@example.org), March 07, 2002
for the 55 & 58mm lenses you will still need a center filter. Physics has not changed.
-- Ellis Vener Photography (email@example.com), March 07, 2002.
The reason for the need of center filters is the fact that the lens is very close to the film plane. I.e. the center of the film is much closer to the lens than the corners. The math/physics for this is about the same as the compensation factor that you have to put in when shooting subjects at close range, i.e. approaching macro range.
This is the way that all WA lenses for non-SLR are built. What you loose with this type of construction is the light falloff. On the other hand, the image quality usually is much better, as compared to the retrofocus (inverted telephoto) designs that are used with 35mm and MF SLR's, because of the mirror.
-- Björn Nilsson (firstname.lastname@example.org), March 07, 2002.
I use the 55mm Grandagon about 50% without CF almost if I do not shift or tilt. The 75 mm Nikon I use to 80 % without CF.
But everyone has his own taste on thad issue.
-- Armin Seeholzer (email@example.com), March 07, 2002.
I have been using a 65mm F5.6 Nikkor and havent found the need to use a centre filter with B&W or Colour which has surprised me. I expected to have to buy one but has proved to not be the case. I only use very small movements, if any as it is primarily used for landscapes - it may be a different story if I wanted more movements. I suggest try one without and only buy if you feel it necessary for your type of photography.
-- David Tolcher (firstname.lastname@example.org), March 09, 2002.
Ellis and Bjorn have answered your question. Some photographers do not seem to notice or care about light fall-off, but with a 55 or 58 lens, it will be present. For some reason the 38mm Biogon does not need a center filter in 6x6 format. I asked about it on the Medium Format Forum, and the only answer offered was that the large diameter of the Biogon's image circle somehow helped. Anyway, I think that a center filter is needed in the 55-58mm range.
-- Michael Alpert (email@example.com), March 09, 2002.
I use the 38 biogon and it has quite a bit of light fall off used open.
-- adrian tyler (firstname.lastname@example.org), March 10, 2002.
Its easy to visualize why the light falloff exists off axis. Imagine your eye at the center of the film plane, looking at the aperture hole. It looks more or less round, doesnt it? Now move your eye to the corner. The 'round' aperture now becomes an elipse. Less light! The shorter the focal length, the narrower the elipse, and the less light at that point on the film.
-- Ron Shaw (email@example.com), March 11, 2002.