Re: Wide-Angle Adapters

[bercov@xxxxxxxxxxx (John Bercovitz)]

I'm not too much in favor of a wide angle adapter unless you can 
find a viewer that's appropriate.  As it is, stereo camera lenses 
are already wider than viewer lenses.  So if any widening is done, 
it will exacerbate the already noticeable problem of stretch.  If 
anything, you want telephoto adapters (which are actually low-
power telescopes).  These will tend to eliminate stretch when 
viewing projected slides.  As Ferwerda said, you want about a 70 
mm focal length for your camera's lenses if the slides are to be 
projected.  That's because the screen is small and far away 
(subtends a small angle of view) from a seat in the audience.
 
It's really very simple: The Realist format is maybe 21 or 22 mm 
wide and the common stereo cameras have focal lengths of 35 mm or 
a little more, a ratio of perhaps 1.7:1.  So you should sit 1.7 
screen widths from the screen to get a proper view if the screen 
is filled with the Realist image.  This means:
 
Screen width in feet        Distance to the best seat in feet
 
         4                                 6.8
         5                                 8.5
         6                                10.2
         7                                11.9
         8                                13.6
         
I have sat 7 feet from my four-foot screen and it's great.  
Because of the lack of distortion, you really feel like you are 
"_there_", but the problem is there just isn't enough on-screen 
resolution to warrant sitting that close.  Yet another argument 
for longer lenses on the camera.
 
Nevertheless, I'm all in favor of wide angle if it can be carried 
off with proper viewing.  I'm sure that if sitting at the proper 
distance from the screen makes you feel like you're there, then 
sitting at the proper distance from a wide angle view would 
_really_ make you feel like you're there.
 
John B
 


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