Re: Digicam- resolution maximus!

[Kennedy McEwen <rkm@xxxxxxxxxxxxxxxxxxxx>]

In article <143.fb71a1a.2a35860a@aol.com>, Scanlist@aol.com writes

>If I may interject my thoughts into this discussion-
>
>Is the previously mentioned 40,000 dpi capturing scene information from
>the film or just the structural arrangement of the grain? I'd like to
>invert the argument: if there were no grain, and we photographed the
>same scene @ 40,000 dpi using the same lens, same f-stop, onto a same
>sized  CCD (who knows, 25 years from now an entry level camera's chip!)
>would we not be capturing significantly more scene information, having
>eliminated the physical "veil" of the grain, which has its own type of
>"dot" gain-  serious mechanical issues:  grain clumping, light
>scattering, bromide dragging etc.... all of  which adds to a distortion
>of the micro-mosaic representation of of the scene?
>
Imaging at 40kppi resolves up to 20kcy/in.  As already stated, just the 
diffraction limits of an f/8 lens result in a complete loss of contrast 
by 250cy/mm, or 6350cy/in, and an MTF which is already down to 50% at 
2540cy/in.  The slowest aperture of a perfect lens that can resolve 
anything at all at 20kcy/in is around f/2.5, with f/1.0 being necessary 
to achieve 50% modulation.  All of these calculations are based on green 
light at 500nm wavelength - for red light the resolution (or f/#) 
reduces further by approximately 30%!

In short, 40kppi is beyond the capability of practical optics, whether 
the image is captured on film or digitally.  And just for reference, 
40kppi is a pixel size of only 0.635um - about the size of the smallest 
transistor that can be currently made!


-- 
Kennedy
Yes, Socrates himself is particularly missed;
A lovely little thinker, but a bugger when he's pissed.
Python Philosophers
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