Re: the elements of lenses in stereo Viewers

[P3D Dr. George A. Themelis <DrT-3d@xxxxxxxxxxxxxxxxxxxxxxxxxxx>]

Lincoln Kamm asks:
    
>I was just noticing last night that some slides I looked at in a stereo
>viewer (that I am pretty sure has single element lenses) seemed to have some
>color shift or a blure of color that moved when I looked through at
>different angles of the lenses.  Is this because it is single element, or
>could it be something else?  Is there anything I can do to fix this problem?

Hey, my favorite subject!  CHROMATIC ABERRATION!

Yes, this "false color" (usually blue) is caused by chromatic aberration.
As Gabriel pointed out, it gets worse as you move away from the center.
My eyes are trained to detect it in viewers like VM model D, Kodaslide
I (and II!) and all stereoscopes except the ones with achromatic lenses.  
Achromatic lenses have 2 (usually lenses), the second correcting the first.
It is usually easier to see chromatic aberration when looking at a B&W
image.

Nothing can really fix the problem, except for new lenses.  What kind
of viewer are you using?  Perhaps my orginal Revere/Wollensak achromatic
lenses offered at a good price (ooops! wrong list! ;)) can replace
the single-element lenses in your viewer.

Long live achromatic lenses!!!

George Themelis

---
mailto:DrT-3d@xxxxxxxxxxxxxxxx


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