> And the cos^4 falloff on a 24 TS-E with 11 mm shift in the long direction > is about 2.6 steps (assuming a 58.6 mm image circle), which often is OK > for > a sky but is undesirable in other situations. Since I'm not aware of a > center filter (radial ND grad) made for this lens, I'm not sure that much > can be done about the dark edges. >
This can be partially overcome by using pupil distortion. Look through the back end of the lens and rotate the lens off axis. As you increase the angle the apparent size of the aperture *may* increase. This is pupil distortion and it counteracts some of the light falloff. This effect is visible on the 17-35 2.8L zoom. Normally, one of the four falloff cosines is due to the oblique angle that the light passes through the aperture. Instead of being a circle, one axis shrinks with the cosine of the angle, creating an ellipse instead of a circle, and decreasing the area that can pass light to the film. * **** ******* *********************************************************** * For list instructions, including unsubscribe, see: * http://www.a1.nl/phomepag/markerink/eos_list.htm ***********************************************************
