How far apart should the lenses be for stereo photographs?

August 25, 2004 1:53 PM

I'm going to try making some 3D wiggle pictures, like Jim Gasperini's. There's a how-to on assembling the digital images into animated .GIFs here, and a MeFi thread here, but I have a question about taking the pictures themselves. I don't have a special stereo camera. I'm going to try using two disposable cameras strapped to a ruler in parallel, with me manually snapping both shutters at the same time.

Here's the question: How far apart should the cameras (lenses) be?
posted by scarabic to media & arts (6 answers total)

Well, they're supposed to be "eye spacing" which would mean the centers being no more than about a finger length [2.5 inches] apart. This is for a near point of about seven feet, according to these articles. You can move the lenses farther away from each other the farther back you are from your focus point. This is, apparently, rough to do with standard cameras but perhaps you could rig something out of the disposables to do this, or if you're real exacting, you can do it with one camera and just move it to the side between shots.
posted by jessamyn at 2:07 PM on August 25, 2004

"One in Thirty Rule" The stereo base lens separation should be one 30th the distance to the nearest object in the scene. Example: if the nearest object is 30 feet away, the lens separation should be 1 foot. Most stereo cameras are factory set at the interocular distance of 2.6 inches thus suggesting the nearest object should be at (2.6 X 30) 6.5 feet, which is sufficient for average photos of people in the environment. (Burder, David and Whitehouse, Pat p.6)

The reason for this, by the way, is that you want the objects to appear "near" and thus have a visible 3-dimensional body to them. The difference between an infinitely far away object and one that is close is only a viewing convergence of 2-3 degrees. So, to simulate that nearness, take the tangent of that from which you get a ratio of about 1 to 30.

You can use this to back-calculate how near you want an object to appear using simple trigonometry and the fact that our brain assumes we are viewing this at a standard interocular distance.
posted by vacapinta at 2:10 PM on August 25, 2004

Aha. Then perhaps what I want to do is line up 4 disposables together, and snap whichever pair of them is best spaced to handle the distance from the primary subject. Based on the closest I can get them, this means multiples of about 12 feet. I can match the photos all up later.

Excellent resources, thanks!
posted by scarabic at 2:42 PM on August 25, 2004

OT: Gaspirini's seminal "Hidden Agenda" computer game (from 1989) is incredible.
posted by inksyndicate at 3:18 PM on August 25, 2004

jason kottke played around with this last year, and posted some tests and links on his blog.
posted by chr1sb0y at 5:47 AM on August 26, 2004

I just didn't really need to see this.
posted by LairBob at 8:55 AM on August 26, 2004