[Leica] Focomat V35

[mark at rabinergroup.com (Mark Rabiner)]

On 8/31/04 10:37 PM, "Henning Wulff" <henningw@archiphoto.com> typed:

>> 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.


What about a square hole in a circular plate?

Wow far out!


Mark Rabiner
Photography
Portland Oregon
http://rabinergroup.com/