T3D Custom viewer lenses.

[John Slivon <frogs@xxxxxxxxxx>]

>Well, that's the list of specs
>we need to come up with if we want to take the guy up on 
>his offer. 

Well, for starters lets try achromats with no pincushion or barrel
distortion, sharpness to the edges of the field and 40mm focal length and
28-30mm diameter (I wear specs) for 8p realist format pairs. I think that
any shorter focal length would produce too wide a field for comfortable
viewing. For medium format the focal length would be 70-80mm and a diameter
of 35-40mm. I think that the lenses would need to be aspheric for the
realist format slides. (now we're talkin' bucks!) If that makes the price
too high then one of the faces should be either flat or concave to minimize
the pincushion distortion and the edge distortion. Pincushion and edge
distortion are my number one concerns. Magnification is next in importance.
The focal length for the 8p realist format pairs would probably have to be
increased to around 45mm with a diameter of 28-30mm if the design is kept
spheric. 
Am I off base?
JS


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