Re Binocular vs .Stereoscopic

[P3D Peter Homer <P.J.Homer@xxxxxxxxxxxxxxxxx>]

Conrad Beck states in in his book "The Microscope" 1921 "Doubt has been at
times expressed as to whether looking at an object with a single object
glass (objective) can under any circumstances give a really stereoscopic
relief .Those who have worked with a binocular microscope do not retain
such a doubt, and the explanation of the phenomenon is quite satisfactory."
His explanation can not given here without diagrams . Actualy I used such
microscopes for years without noticing any stereo effect even when I first
tried the method of adding red/green filters to the eyepieces and a half
red half green filter in the filter tray which I read about in another book
on microscopy.
   More recently I came across a simple method for measuring under the
microscope which did not invovle an eye piece graticule just the stage one
to measure the diameter of the view and you then estimated the fraction of
the diameter occupied by the specimen . For some reason the method asked
for a binocular microscope which actualy caused a problem and if it actualy
meant a stereoscopic microscope that would have been worse. When I cheked
the measurement with the stage graticule I kept getting two slightly
diffferent results so I closed one eye and then the other and realised
there was a slight difference in parralax between the two of about 1/2 of
1/10 millimetre and my brain was alternately selecting one view and then
the other. This was using a Watson system 70 with one objective. Trying
other magnifications I found the difference decreased with higher
magnifications and was less than the 1/30 rule would suggest so I thought
the actual stereo effect might be unnoticeable .
  Trying the anaglyph method again I found I got a stereo effect using
relatively large specimens with no coverslip to flatten them and when I
removed the filters it was still there and I thought at first the filters
had no effect but I since decided they do improve the effect as does the
crossed polaroids method I have tried since. The effect seems to differ
between makes of microscopes our Kyowas work even better for me than the
Watsons also a Zeiss and
Gillet and sibert but a Vickers M14 Photoplan is not so good. P.J.Homer



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