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<p class="MsoNormal">Sorry, I didn’t read Ben’s original post carefully enough; he’s right that you can rotate cameras under the restricted display conditions he articulates. My main message was to explain why it doesn’t work in more typical methods of stereo
viewing. <o:p></o:p></p>
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<p class="MsoNormal"><b><span style="font-size:12.0pt;color:black">From: </span></b><span style="font-size:12.0pt;color:black">Ben Backus <ben.backus@gmail.com><br>
<b>Date: </b>Monday, 23 March 2020 at 10:25 am<br>
<b>To: </b>"James P. Herman" <hermanj@gmail.com><br>
<b>Cc: </b>Michael A Crognale <mcrognale@unr.edu>, Barton Anderson <barton.anderson@sydney.edu.au>, David Peterzell <davidpeterzell@me.com>, cvnet <cvnet@mail.ewind.com>, Christopher Tyler <cwtyler2020@gmail.com>, "visionlist@visionscience.com" <visionlist@visionscience.com>,
David Peterzell <dpeterzell@berkeley.edu><br>
<b>Subject: </b>Re: [cvnet] [visionlist] Trying to demonstrate stereoscopic vision remotely<o:p></o:p></span></p>
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<p class="MsoNormal">Thanks James for that. <o:p></o:p></p>
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<p class="MsoNormal"><span style="font-family:"Arial",sans-serif">You know, to be honest I don't think this matters for an introductory lecture on stereo. Stereo effects are pretty robust. There's no harm free-fusing pictures taken with toe-in cameras. You'll
still get a nice stereo effect. Better to get students trying things, right?</span><o:p></o:p></p>
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<p class="MsoNormal">This is probably not appropriate for most students, but technically, you *can* use toe-in cameras to perfect effect, if the stereo images are displayed in a haploscope, with the arms set to the same convergence angle as the amount of toe-in.
In that case the optic arrays would be preserved, so both the perspective and the vergence demand would be correct. That could be the situation Mike C had in mind when he asked the question (either that, or else convergent free fusion of the two images), whereas
I was describing what happens when images are displayed in a standard stereoscope or movie theater.<o:p></o:p></p>
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<p class="MsoNormal">On Sun, Mar 22, 2020, 2:36 PM James P. Herman <<a href="mailto:hermanj@gmail.com" target="_blank">hermanj@gmail.com</a>> wrote:<o:p></o:p></p>
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<p class="MsoNormal">Ben --<o:p></o:p></p>
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<p class="MsoNormal">My apologies but I found your answer(s) to Michael Crognale's question difficult to follow, and I was also perplexed by the notion that translation and not translation+rotation is the way to go for DIY stereoscopy!<o:p></o:p></p>
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<p class="MsoNormal">I found a website that describes the problematic (but not impossible to contend with) distortions of perspective induced by using "toe-in" (relative camera rotation in addition to translation) when taking stereoscopic images.<o:p></o:p></p>
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<p class="MsoNormal">The short answer is that if you rotate the camera in addition to translating it (between taking photos), the change in perspective can result in identical parts of an image having different sizes in the two photos (the dangerous vertical
disparity mentioned previously). I must admit it's not clear to me why any movement of the camera wouldn't potentially cause such distortion, but I suspect it's a matter of scale (translation causes little distortion, rotation causes more). In any case, here's
the link:<o:p></o:p></p>
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<p class="MsoNormal"><a href="https://protect-au.mimecast.com/s/bvhkC0YKPviJnWY5Hw6aa3?domain=binocularity.org" target="_blank">http://www.binocularity.org/page12.php</a><o:p></o:p></p>
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<p class="MsoNormal">Enjoy!<o:p></o:p></p>
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<p class="MsoNormal">-- jph<o:p></o:p></p>
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<p class="MsoNormal">-- <o:p></o:p></p>
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<p class="MsoNormal">James P. Herman, PhD<br>
Laboratory of Sensorimotor Research<br>
National Eye Institute<br>
Building 49 Room 2A50<br>
National Institutes of Health<br>
Bethesda, MD 20892-4435<br>
office: (301) 496-9376<br>
mobile: (212) 663-0407<o:p></o:p></p>
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