The whole point of a smaller aperture is that it mechanically vignettes off the lower resolution parts of the image circle. Guess that's why they termed em Commercial Ektars. Portrait studios typically wanted faster aperture, shallower depth of field, and weren't as concerned about corner resolution, so coveted 4.5 versions. Someone else can describe the specific Ektar options better than me; but Zeiss and others had more than one speed/size selection of tessar. I have a Zeiss f/9 360 barrel process tessar that is extremely sharp over its whole image circle, but still renders lovely out of focus background blur. By contrast, my Nikkor M's are thin elements for a tessar design, especially contrasty, being multicoated, but also clinically sharp with the busy annoying background blur typical of Nikon LF lenses, so wonderful for intentionally sharp landscape subjects, but not ideal for anything "dreamy". The 300 M is extremely sharp on 8x10, but with very little to spare, so not really very versatile on this big a piece of film. I mostly enlarge my negs, so a contact printer might have a more liberal definition of usable image circle than I do, as well as at how small a stop detail rendition becomes unacceptable. Probably very few ULF shooters enlarge their negs. And certain applications, like studio portraiture, don't require significant tilts or rises. So it's all relative.
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