Re: Effective FL after correcting for myopia

[P3D Dr. George A. Themelis <fj834@xxxxxxxxxxxxxxxxxxxxx>]

>How would one go about calculating the new effective FL?

Think of the effective FL as the distance of the lenses to the slide.  If
you inrease this distance when your refocus the viewer then you inrease the
FL and visa versa.

>I did an experimental conversion of a $3 viewer to use a pair of DrT's
>"new old stock" Revere viewer lenses.  The result might be called a
>PT'd 3-$ (or using D for DDDolar, a PT'd 3D) ;).  Advance notice:
>this 1st prototype, which undoubtedbly will be extrememely valuable
>to collectors in the future, just might show up on Sell-3D someday! ;)

I believe I have the 1st prototype ;)

>Unfortunately, significant chunks of the corners of each image are
>lopped off when I view a 5P Realist image with these lenses (which is
>*not* a problem with an unmodified $3 viewer.  Do eyeglass wearers have
>this problem with Red Button and other Realist format viewers with a
>shorter FL than the $3 viewer?)  

Eyeglass wearers have usually a problem seeing the 7p (not 5p) image in the
red button.  It all depends on the thickness of your glasses and design of
the viewer.  The field of view decreases as you increase the distance of
your eyes from the lenses.  I think John B. has mentioned that because of
his thick glasses he can hardly see the 5p in the red button so 7p is
beyond the question. 

>I can see a very
>noticeable reduction in the stretch of my slides using the PT'd 3D in
>this manner, as compared to an unmodified viewer.  I also think I can
>see a difference in the stretch of the scene from the PT'd 3D with my
>glasses on as compared to the same scene with the lenses pushed in
>closer and my glasses removed.  I'm trying to get an objective measure
>of the realative magnitude of these two effects.

Still, you have not mentioned if you like (prefer) the strech or not!

George Themelis


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