Re: Viewer interocular

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

>Paul Talbot writes:
>
>>I have noticed that some mounting problems can seem to magically disappear
>>as the interocular is changed.  Before describing my theory as to why this
>>is so, I'd like to hear thoughts on the question "What is the proper way
>>to set the interocular of a stereo slide viewer?"

Greg Kane replies:

>The proper way to set the interocular is:  with the optical center wider 
>than the stereo pair's inifinity point separation.

[details on "wedge" lenses & optical/physical centers deleted]

>  The "optical center wider than the stereo pair's inifinity point 
>separation" also applies to Red Button, Green Button, etc viewers, whose 
>optical and physical centers are identical.


Question:  Why wider and not equal to?  Especially if the infinity point 
separation represents a point of real infinity.  If wider, then how much
wider?

I agree with the answer stated as "equal or wider than".  In practice, most
people set it wider so that the eyes converge.  The size of the lenses and
the interocular spacing of the observer are also factors that might
influence the choice of what feels most comfortable.

I do not know what theory Paul has in his mind.  I do not see how the
choice of interocular can affect the mounting alingment problems except for
two cases:  If the lens' alignment in the viewer is affected by the
interocular setting (unlikely but happens from time to time), or, if the
interocular is set so wide that the out of alignment points are not fused.
Maybe for some people the convergence of their eyes affects the degree of
discomfort from viewing misaligned slides.

-- George Themelis


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