Archived posting to the Leica Users Group, 1999/10/13

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Subject: Re: [Leica] CCDs - one more thing
From: Byron Rakitzis <leica@rakitzis.com>
Date: Wed, 13 Oct 1999 23:23:05 -0700 (PDT)

> When someone makes a really good CCD back that will take 
> my Leica lenses, it would be nice if the format were 
> 36X36 mm, NOT 24X36, so as to use the full image circle.
> Since the Camera wouldn't need storace space for film
> and transport, it could still be quite compact. 50%
> more image area would go a long way in terms of improved
> resolution. 
> 
> Now *that* would be neat! Though I couldn't use the
> rectangular shade for my 35 Summilux ASPH...

Well, that would be nice except I bet the image circle for a Leica lens
(or any other 35mm lens make) would not cover 36x36.

Assuming that the lenses are designed to barely cover 24x36 at infinity,
then the radius of the image circle is

		sqrt((24mm/2)^2 + (36mm/2)^2) ~= 21.6mm.

i.e., the hypotenuse of the right triangle formed in each quadrant of
the frame between the origin, the corner of the frame, and its projection
onto the x-axis.

The largest square that will fit in this circle will have a diagonal
of twice the radius, so the sides will measure

		sqrt((21.6mm*2)^2 / 2) ~= 30.5mm

Well, 30x30 wouldn't be bad, but you would have to give up a bit
of the length on a 24x36mm frame.

For me anyway, 24x36 looks like a strange aspect ratio the more I use it
and compare it against square negatives and the print ratios 4x5 and 8x10.

Who knows, maybe it would be better to burn circular pictures onto 43x43
square frames, and then crop in the darkroom to whatever aspect ratio
you care to squeeze out of that circle!

Byron.