[Leica] Focomat V35

[henningw at archiphoto.com (Henning Wulff)]

>At 8:56 PM -0700 8/31/04, Mark Rabiner wrote:
>
>><snip>
>
>
>
>>And there are enlarger lenses which stop down not with a variable aperture
>>with leaves, "the leaves" but with plates with perfect holes in them.
>>Why This kind of thing is a big deal for enlarger optics over camera optics
>>why I don't know. Maybe Erwin does. Or Richard Knoppow of the RUG. Or one 
>>of
>>US even! Tom A?!
>
>A perfectly circular stop ('Waterhouse' stop) has the least edge 
>length for the amount of light passing, so diffraction effects are 
>at their minimum. Diffraction is more of an issue in enlarging that 
>taking, as a print with sharp grain and slightly diffuse objects 
>looks 'sharper' than a picture that doesn't have sharp grain. f/22, 
>and even f/16 can kill sharp grain in a print.

.....it's a 'Waterhouse' stop because it's a plate with a perfectly 
circular hole in it, not because it's perfectly circular. Mumble, 
mumble, mmbmle....

Sorry.

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    *            Henning J. Wulff
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