io newbie questions

Started Apr 8, 2012 | Discussions thread
Turbguy1 Contributing Member • Posts: 942
Re: io newbie questions

1. What exactly does io stand for?

INTER OCULAR (actually should be called interaxial with cameras, but so be it).

2. Does it mean the same thing as Stereo base?

Pretty much, as long as the "sensors" are centered behind the lenses (they are not centered on some older film cameras, for stereo window control), AND the axes are parallel.

3D can be captured with converging axes, where IO can be varied somewhat, but depth captured (depth budget?) needs to be very shallow (say only 2-3") in a close-up shot, where there are no closer or more distant subjects. Also, "keystoning" distortion from converging will/may need correction digitally in post. This correction will crop out some amount of image capture. The larger the convergence angle, the greater the cropping in post.

3. Is io important on the 3d camcorders like the TD10 & SDT750. They seem to have a really small io but no one seems to care about that on these cameras.

Assuming the axes are parallel, it depends on the depth range you want to capture and display WITH COMPORT for the viewer. If you want to capture a depth range (budget?) of from 6" to infinity, you need a small IO, but then perceived 3D begins to "fad out" quickly (say with 5 feet). If you want to capture and display from 6' to infinity, then a 2 1/2" to 3" IO works well, and the 3D "fads out" at about 30'-40'. If you want to show depth at greater distances, larger IO's are needed, but the closest object must be pushed farther away, too. IO is one of the most important metric of stereo work, yet surprisingly few OEMS specify it!

In any event, there's plenty of good 3D to be captured with small IO's.

4. Are there any good resources on how io interacts with focal length and the distance to the subject matter?
Yes, see the stereophotographer's bible (a little out-dated now).

The World of 3-D

A Practical Guide to Stereo Photography
by Jacobus G. Ferwerda

available here...and other books on the same page may be if interest.


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