Re: Viewer interocular

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

>Greg's description suggests that when sharing a 50s slide viewer
>with a group, the interocular should be set for each slide and left alone
>as it is passed around.  Is that the intended use of the lever?  

Yes and no.  If the slides are mounted properly then the lever should not
be changed at all.  That's why viewers without interocular adjustment work
well too.  Some people go to the extreme to say that viewers should not
have interocular adjustment at all (and many of them do not).

>I had
>always believed that each individual would need to adjust the lever to
>accommodate their eye spacing (which, I have heard recently, would not
>be necessary if the viewers were built with adequately large lenses).

Let's put it this way:  If the lenses are sufficiently large then they can
accommodate a variety of eye spacings so the interocular does not need to
be changed.  If the lenses are small then a person might want to change the
interocular to see the slide better (or see it at all in some cases).

>(Note to DrT: this is not intended to incite a passioned defense of the
>Realist engineers who designed the RB!)

I have never defended any Realist engineer... BTW, the person who designed
the red button is Seton Rochwite, the same person who designed the Realist
camera and a few more cameras and viewers.  There is an interesting
interview of SR (same initials as Stereo Realist) by Mark Wilke sometime
back in Stereo World...

>Here is the method I have adopted for setting the lever:
>
>I first close my right eye and position the viewer so that my left
>(dominant) eye can see 100% of the left image (just barely possible with
>eyeglasses on).  Then, with only the right eye open, I adjust the lever
>so that I can see 100% of the right image.  For me, there is only one
>point (the extreme close setting) at which I can see 100% of each image,
>so there is no possibility of any slide-by-slide adjustment of the lever
>without losing information from one image or the other.

Apparently you are adjusting the viewer to maximize your field of view. 
Does you method change when you take your glasses off?  Do you adjust it
for each individual slide?  What is your eye-spacing?  Apparently you are
viewing slides with some convergence even at infinity.  Most people use it
like that.  I used to do that and then realized that bringing the lever
closer to the center was OK too and some times better...

You mentioned earlier that this method gets rid of misalignment.  What
misalignment is that?

-- George Themelis


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