Re: [photo-3d] Re: Loupe question, magnifiers, confusion

["Dr. George A. Themelis" <drt-3d@xxxxxxx>]

I think there is a mistake in your analysis:

>   Magnification = 250mm/FL + (10 * x**-1)
>
>If we could focus on an object at 0 inches distance, the formula
>would describe the intrinsic magnfication offered by the lens itself:
>
>   Magnification = 250/FL + (10 * 0**-1)
>
>   Magnification = 250/FL + 0   

This is incorrect.  If x = 0 then x**-1 (essentially 1/x) is
infinity, not zero.  Zero is achieved when x = infinity
or when the we focus at infinity, which happens when
the eye muscles relax.

In presenting this general formula you are assuming that the 
user WANTS to achieve the closest focusing distance.
This usually strains the eyes and it is not necessarily
desirable.

Personally, I prefer to have my eye muscles relaxed when
I view stereo slides (or even when using microscopes or 
other optical instruments), therefore I focus the viewer 
for infinity viewing, which gives:

Magnification = 250mm/FL

George Themelis