Re: format image comparisons

[bercov@xxxxxxxxxxx (John Bercovitz)]

I hope I'm not posting the same thing twice.  Sometimes I forgets.  8-(

Yesterday I was saying it was harder to make a short lens that covers a
wide format than a long lens that covers the same (angular) width format.  
This is because regardless of format size, you need a large diameter lens 
near your eye to cover all the directions your eye will look in when it's 
viewing a wide format.  A large diameter lens of short focal length is a 
contradiction.  Near the edges of such a lens, the curvature of the lens 
will be very large leading to gross aberrations.  As I said a few years ago, 
I think the thing to do is to make a close-focusing telescope to view the 
images.  It's a lot more complicated than a simple achromat but it would 
allow the use of reasonable, low-aberration lenses.

John B


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