HUGE Image Circles (lens coverage)

[scootermm]

MASSIVELY overrated. What do you think? Everyone's so hung up on this. I spent COUNTLESS hours trying to figure out which lenses had the biggest coverage - even to the point of considering a 150 grandagon for my normal lens on 4x5. I'm an architectural photographer, too - so you'd think it would be important to me. When I do lens rises - they tend to be pretty subtle - rarely more than 10-20mm. And QUITE often I use 5mm or less. I even think it's quite refreshing not to use ANY. More than 10mm on 4x5 just starts to look kind of silly IMHO. Others' opinions?

thought maybe Id spark the initial flames on this conversation...
speaking from my experience in 4x5, then 8x10, and now 7x17 (along with much 8x10) I like lens coverage. one of the downfalls of my one and only 7x17 lens (14" Kodak Commercial Ektar) just doesnt give me the coverage I wish it would. although Im fine working within the constraints but having some more of an image circle would be gladly appreciated. so to state its massively overrated is something I couldnt disagree with more. Id much prefer to have excess coverage thats never used then not enough coverage that vignettes negs.

[Murray@uptowngallery]

If it's typical for edge resolution to be worse than central resolution with many lenses, is 'excessive' coverage a blessing in disguise with regard to resolution deterioration at edges?

I suppose degree of enlargement trumps this supposition. Is there any connection between physical aperture diameter and edge resolution? It would seem that they necessarily interact but might be independent in theory. Diffraction-limitation and ab errations are discussed in totally different 'chapters' both both coexist in an exposure.

Murray

[Sparky]

Well, I don't know QUITE how to answer that except that the extra image circle only seems to be available with increasing aperture number - and the trade off is image circle vs. diffraction - the greater your image circle the greater the amount of diffraction overall. Apart from inherent aberrations/effects native to off-axis use, the entrance pupil seen from the edges is distorted (american football shaped) and I suspect you're getting increased diffractive effects there in addition to off-axis aberrations. But anyway - that part of the image would not exist at a lower aperture number. So I suppose it is what it is - and there's no improving on it that I can see - but yes, lower magnification enlargements would certainly help matters!