Close-up cameras

[P3D Bob Aldridge <bob.aldridge@xxxxxx>]

John R wrote:

->My visualization (as of 3AM on a Friday night :-) is that installing a
->divider won't change the optical paths, though it will block some of
->the light. Instead of two small images (left and right view), you'll
->end up with a full-size but dark image, with a black line through the
->middle. 
->Mrs. Whitehouse used to take two lenses and grind away one side of
->each (but not all the way to the center - when looking at a lens from
->along its axis, picture it not as a circle but as a "D" shape), then
->cement the two partial lenses together side by side along the ground
->edges, and mount this assembly in a camera with a divider as you
->describe. This allowed her to take close-up stereo pictures with an
->interocular less than the diameter of the lenses (many of these
->pictures were of bird nests). Since the system really uses two lenses
->for the left and right views, keystoning is not an issue. The
->effective interocular is the distance between the centers (optical
->axes) of the two lenses. 
->A few years ago, I tried to come up with a way to do this for SLRs,
->possibly by modifying close-up lenses. I put it off as being too
->time-consuming, but that doesn't mean it can't be done. If you get
->something working, I'd appreciate hearing about it.
-> 
->John R

1) Pat Whitehous used two ground down lenses as you described, but David
Burder (& others) have managed quite well with a single lens, but with a
pair of stops. These then work through the edges of the lens and the
prismatic effect then spreads the beams into two images.

2) The attachment for an SLR is called a "Clemetson attachment" and
usually have a pair of cut down lenses with a divider in FRONT of the
lenses. This acts as a "septum" to stop the two images from overlapping.

Best of luck

Bob Aldridge
Stereoscopic Society Projectionist
---
 * POW 2.0  0007 * ... An optimist is just an inexperienced pessimist!


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