Re: detail

[P3D Gregory J. Wageman <gjw@xxxxxxxxxx>]

Ron Labbe wrote:

>freeviewing isn't much good for fine detail, either

That's a rather meaningless statement without further qualification.

My recollection (possibly faulty) is that Holmes-Bates stereoscope
lenses are of a relatively long focal length, maybe 80-100mm?  (Please
correct me if I'm wrong.)  This equates to a magnification of about
250/100 = 2.5x to 250/80 ~= 3x using the rule-of-thumb of mag ~= 250mm/f.l.

Assuming one freeviews at the nominal 250mm (~10 inch) distance, then
the question becomes how much of the increased magnification and ability
to see fine detail of the stereoscope is traded off against its increased
distortion, chromatic aberration (most 'scopes aren't achromatic) and other
optical imperfections?  For example, I find the severe chromatic
aberration of the plastic "Added Dimension" lorgnette viewers so bad
that it more than offsets whatever magnification it offers.  That is,
I can see the print more clearly when freeviewing than when using one
of these viewers.

	-Greg W.


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