Lens' alignment

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

Peter Abrahams detailed his technique for checking binoculars for 
alignment.

> The typical user test for collimation is to view a dot or small object,
>then slowly move the binoculars away from the eyes, keeping the dot in the
>field of  both oculars.  If you can see it in both when a foot or so away
>from your eyes, alignment is good.

I use the same method to check viewer lenses for alignment.  I bet
you never thought that a viewer can have misaligned lenses!  Yes, it
can happen.  It is a terrible problem because, without training,
you think that something is wrong with your slides or 3d in general.
The viewer is the last one to suspect....

To check the lens' alignment I use a slide that I know is properly
aligned.  Many times I can tell how well the lenses are aligned by
just looking at the slide and alternating eyes.  A beginner will have
better luck focusing at an object that the center and backing off, 
just like Peter described.  Misalignment will be obvious.

Notorious viewer for misalignment:  Realist green button.  Red button
viewers do not have this problem often... same for Kodaslide.

George Themelis


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