for math freaks

[P3D John Bercovitz <bercov@xxxxxxxxxx>]

I'm looking at a Topcon for a member of this list.  It's 
a small-stereobase (macro) unit that can be fit to a 35 mm 
camera.  I'll set it up with no focus adjustment and then 
insert spacers (extensions) to give it discrete close-up 
focussing distances.  When calculating the lengths of the 
extensions, it's easier to use the Newtonian form of the 
lens equation (xx" = f*f) that the familiar Gaussian form 
(1/f = 1/s + 1/s').  To show that the two formulae are really
the same, I've made a gif called "newtgaus.gif" and Bob has put 
it in photo-3d's anonymous ftp directory.  If you're interested,
you can get it from bobcat.etsu.edu by cd to pub/photo/photo-3d/
technical.  When you download, don't forget gifs are binary.
 
John B


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