View Full Version : Light fall off on newer style WA lenses

Mike Kuszek
7-Mar-2002, 15:27
Is there any brand of perhaps the newer style lenses that do not need a center f ilter 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?

Ellis Vener
7-Mar-2002, 15:39
for the 55 & 58mm lenses you will still need a center filter. Physics has not changed.

Bjorn Nilsson
7-Mar-2002, 16:32
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.

Dave Tolcher
9-Mar-2002, 03:26
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.


10-Mar-2002, 08:30
I use the 38 biogon and it has quite a bit of light fall off used open.

Ron Shaw
11-Mar-2002, 12:06
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.