Re: stereoscope spec's

[P3D Alan Lewis <dlewis@xxxxxxxxxxxx>]

Greg Kane writes:
> 
>     Holding a scope up to the sky and using it to focus the sun on a
> piece of paper lets you measure the scope's focal length.  The other
> thing you can measure is the distance, on the paper, between the two
> focused suns.
> 
> ? Am I correct that this between-the-suns distance is also the physical
> distance between the optical centers of the two lenses?

Answer: yes


 
> ? Is this also the maximum infinity point separation for mounted prints
> used with that scope?


Answer: technically yes.


> ? Does the maximumn inifinity point separation differ from the *ideal*
> IPS?

Answer: As far as I know there is no ideal IPS. Antique views used 
different standards for infinity separation, and for window placement.  
As long as the max. inf. separation on your view doesn't exceed the 
optical centers of those particular lenses then viewing should be 
comfortable.  
Not all viewers have the same optical centers, and not all people have 
the same eye spacing.  Everything is a compromise.
In my opinion, don't worry too much about an ideal separation.  You will 
determine your own comfortable inf. separation by experimentation, and 
that is all that matters.  Switching between viewers with minor 
differences in optical centers won't really be noticed. 



> For the widely available Added Dimension lorgnette viewer this distance
> measures about 4 inches -- ? Is that the maximum infinity point
> separation for this viewer?

Answer: I think so.  This viewer is used sometimes for larger than 
Holmes/Bates format views. 

-- 
_______________________________________________________________
Alan Lewis
mailto:dlewis@xxxxxxxxxxxxx
Home of the stereo wedding package, and weekend stereo projects
http://www.arlington.net/homes/dlewis


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