[visionlist] [cvnet] Trying to demonstrate stereoscopic vision remotely

Barton Anderson barton.anderson at sydney.edu.au
Sat Mar 21 23:21:19 -04 2020 

Note on stereo photography:  You should only translate the  camera horizontally, you should NOT rotate it to keep an  object of interest in the center of the image.  Rotation will induce vertical disparities that are unfusable.  There’s some good instruction here:

https://books.google.com.au/books?id=6CzuydFlMpwC&pg=PA129&lpg=PA129&dq=should+you+rotate+the+camera+when+taking+stereo+photos&source=bl&ots=B0vEcTopGt&sig=ACfU3U08DiG1SGznUn0ImCUfV0jUiOutSg&hl=en&sa=X&ved=2ahUKEwiihImmjq3oAhW0guYKHQ2jDYoQ6AEwEXoECA0QAQ#v=onepage&q=should%20you%20rotate%20the%20camera%20when%20taking%20stereo%20photos&f=false

-Bart Anderson


From: visionlist <visionlist-bounces at visionscience.com> on behalf of Lester Loschky <loschky at ksu.edu>
Date: Sunday, 22 March 2020 at 9:11 am
To: David Peterzell <davidpeterzell at me.com>
Cc: David Peterzell <dpeterzell at berkeley.edu>, cvnet <cvnet at mail.ewind.com>, Christopher Tyler <cwtyler2020 at gmail.com>, "visionlist at visionscience.com" <visionlist at visionscience.com>
Subject: Re: [visionlist] [cvnet] Trying to demonstrate stereoscopic vision remotely

Love it, David!  I've made those on my own as well, but it hadn't occurred to me to teach students how to do it.  I think that really will make the concepts very concrete for them.  And, as Christopher mentions in his Scholarpedia page, crossed eye viewing is easier for most people than the "look through" method, so I think a lot of students can get that to work.  Wonderful idea!

Best wishes,

Les

On Sat, Mar 21, 2020 at 1:56 AM David Peterzell <davidpeterzell at me.com<mailto:davidpeterzell at me.com>> wrote:
In addition to showing them Christopher Tyler’s Stereogram (using Magic Eye examples), I do my best to teach them to free fuse. If that goes well with a few of them, then I teach them how to make their own stereo photos using the cameras on their smart phones.  1. Have your subject hold still.  2. Take a photo.  3. Take a second photo with the camera moved just a couple inches to the left or right, still centered on the subject.  4. Put the photos in something like PowerPoint. 5. Crop and realign the photos as needed (crossed or uncrossed). 6. View  This isn’t for everyone, and some people get headaches.  But I’ve had many students have a blast with this once they learn this. It has always seemed to me to be a good way to teach about stereoscopic vision and the construction of binocular depth perception.

Here are just a few of my own examples, all made on the spot with an iPhone.  These sets are made for crossed not uncrossed viewing.  If they appear small, click on them to open them.  Who can find the Serbian vision scientists?

Dave


David Henry Peterzell, Ph.D., Ph.D.
--Professor, John F. Kennedy University, Clinical Psychology Doctoral Program, College of Psychology
--Visiting Scholar, University of California, Vision Science Program, School of Optometry

JFKU Top Minds video:
http://blog.jfku.edu/john-f-kennedy-top-minds-professor-david-peterzell-phd/<https://protect-au.mimecast.com/s/IfNFC81V0PTOkqgjInUxz5?domain=blog.jfku.edu/>

[cid:image001.png at 01D60054.FD1E90E0]

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Click on this one to view.  (crossed and uncrossed)
[cid:image018.png at 01D60054.FD1E90E0][cid:image019.png at 01D60054.FD1E90E0]

[cid:image020.png at 01D60054.FD1E90E0]



On Mar 20, 2020, at 9:50 PM, Christopher Tyler via cvnet <cvnet at lawton.ewind.com<mailto:cvnet at lawton.ewind.com>> wrote:

You could try autostereograms, such as the examples on my Scholarpedia page<https://protect-au.mimecast.com/s/oO48C91WPRTROqjmUE0rVx?domain=scholarpedia.org>.  Not everyone can get them, but they're pretty effective for those who can.

All the best,
Christopher

On Fri, Mar 20, 2020 at 9:35 PM Lester Loschky <loschky at ksu.edu<mailto:loschky at ksu.edu>> wrote:
Hi Everybody,

If you teach Sensation and Perception, and are currently preparing to teach it remotely, you may have the same question I have: how can you demonstrate stereovision remotely?

As preface, the following are methods I have used in in-person classes to demonstrate stereo vision:

  1.  an actual stereoscope and example stereoimages to share with students (including the classic Julesz square tile random-dot-stereogram image)
  2.  example stereoscopic lenticular lens images to share with students
  3.  red/green anaglyph images with sets of cardboard & plastic red/green anaglyph glasses
  4.  Google Cardboard plus cell phone to share with students
  5.  random dot autosterographic images
  6.  touching two pen tips together using two eyes versus one eye
  7.  learning about crossed vs. uncrossed disparity using two fingers at different distances
Unfortunately, my students don't uniformly have access to the apparatuses required for 1-4 above.

Re. # 3 (red/green anaglyph images), I've thought of having students order a single pair of red/green anaglyph glasses online.  However, it appears that the cardboard and plastic ones can only be purchased in bulk. (I guess they're too cheap to sell individually.)  They also might not arrive in time, but students could still enjoy them once they get them.

Re. #4 (Google Cardboard), I recall getting a free Google Cardboard from the NYTimes several years ago.  However, they are now no cheaper than $5 (Irisu, of India), and likely wouldn't arrive in time.

Regarding option #5 (random-dot autostereograms), I have found that since seeing random dot autostereographic images in depth requires perceptual learning, a large proportion of students don't manage to learn (within the short time period given in a single class period).  (Of course, many students may have a lot of time on their hands now, so they might keep at it long enough to learn to perceive them.  But there will definitely be a good proportion of students who don't try long enough to learn, and so don't get it.)

#6 (touching two pen tips together) is definitely something that can be done remotely.  However, it doesn't have the "Wow!" factor of other demonstrations.  It is more of an "oh, really..." experience to realize how much worse you are with one eye than two.

#7 (using two fingers at different distances to teach crossed vs. uncrossed disparity) can definitely be done remotely.  It is very educational, but again does not have the "Wow" factor.

There is also the finger "hot dog" illusion, which can be done remotely.  It is interesting, but quite different from all of the others in that stereoscopic depth perception is not involved.

For the related phenomenon of motion parallax, "wiggle vision" is a very nice demonstration:
http://www.well.com/user/jimg/stereo/stereo_gate.html<https://protect-au.mimecast.com/s/yE-gC0YKPviJyBz2H2LFMq?domain=well.com>
https://www.3dwiggle.com/2016/06/28/5-wigglegrams-you-need-to-see-before-you-die/<https://protect-au.mimecast.com/s/z49PCgZ0N1iPByJlH3ksyC?domain=3dwiggle.com/>

Of course, depth perception from motion parallax is importantly theoretically related to stereoscopic vision (both involve two different images from two different views, one seen over time (and only needing one eye)--motion parallax--and the other seen simultaneously (and requiring two eyes)--stereovision).  But it is not the same as stereoscopic vision, so is a separate but related issue.

For the related phenomenon of binocular disparity, there is the famous "hole in your hand" illusion using a cardboard paper towel roll.  If students have a spare cardboard paper towel roll, they can do this remotely.  But, again, it is a theoretically related but separate issue.

Any other suggestions would be appreciated.

Best wishes,

Les
--
Lester Loschky
Professor
Associate Director, Cognitive and Neurobiological Approaches to Plasticity Center
Department of Psychological Sciences
471 Bluemont Hall
1114 Mid-Campus Dr North
Kansas State University
Manhattan, KS  66506-5302
email: loschky at ksu.edu<mailto:loschky at ksu.edu>
research page: https://www.k-state.edu/psych/research/loschkylester.html<https://protect-au.mimecast.com/s/XYyACjZ1N7ilOm0jS1y030?domain=k-state.edu>
lab page: http://www.k-state.edu/psych/vcl/index.html<https://protect-au.mimecast.com/s/awZ8Ck81N9tYwBvnF8nvws?domain=k-state.edu>

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--
Lester Loschky
Professor
Associate Director, Cognitive and Neurobiological Approaches to Plasticity Center
Department of Psychological Sciences
471 Bluemont Hall
1114 Mid-Campus Dr North
Kansas State University
Manhattan, KS  66506-5302
email: loschky at ksu.edu<mailto:loschky at ksu.edu>
research page: https://www.k-state.edu/psych/research/loschkylester.html<https://protect-au.mimecast.com/s/XYyACjZ1N7ilOm0jS1y030?domain=k-state.edu>
lab page: http://www.k-state.edu/psych/vcl/index.html<https://protect-au.mimecast.com/s/awZ8Ck81N9tYwBvnF8nvws?domain=k-state.edu>
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