Re: 10x Magnifiers for Stereo Viewer

[klein@xxxxxxxxxxxxxxxxx (Alexander Klein)]

bercov@xxxxxxxxxx (John Bercovitz) writes:

> Alex writes:
>  
> > I just came home from a photo-show. I couldn't resist to buy two focusing
> > 10x magnifying lenses to build a stereo viewer.
> [stuff deleted]
> > The lenses have a 23 mm diameter, and the Triplet's magnification is
> > approx. 1/3 less than that of the Realist Red Button viewer.
>  
> Some things don't quite agree here, I think, Alex.  
>  
> First the magnification doesn't seem right.  The red button has lenses 
> maybe 43 or 44 mm in focal length.  The "magnifying power" of a red 
> button lens, then, is 250/43 = 5.8X conventional, or 6.8X advertising 
> (advertisers get to add 1 for focussing in so that the virtual image is 
> at 250 mm instead of at infinity).  A 10X magnifier's focal length would 
> be 250 over 10 or 9, say 9, which is 28 mm.  So the 10X would give much 
> _more_ magnification than the red button's lens, not less.

Sure, the whole SYSTEM (consisting of one triplet and a PCX lens) has a
10x magnification. But the triplet itself (when removed from the assemb-
ly, i.e. less the PCX lens) has a smaller magnification than the Realist
Red Button viewer.

The focusing lenses should give me a GREAT View-Master viewer...

alex


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