Not to quarrel, but when the lens is wide open how can the diaphragm cut off the outer part of the cone of light that the lens projects?Originally Posted by Satinsnow
About field stops, take a look at Rodenstock's published MTF and illumination curves for the 75/4 Apo Rodagon D 1:1. They're flat to the edge. I had one, it gave even illumination across an 80 mm circle as claimed, and beyond that all was dark. Its a wide angle lens with a stop.