Photo Engineer
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I think the possible causes of 3-D have been examined in a general way. And it appears that there are a few reports of other papers being capable of causing such illusions.
As far as the urban legend part, I think that is still up in the air other than one comment that Azo is a rather unremarkable paper when compared to other papers.
I suspect than any good FB contact paper would work well.
I'm curious. What was the actual diameter of the lens opening? Not the f-stop, but the focal length divided by the f-stop. How does it compare with the width of elements of the picture that define relief? (Of course I'm crazy. You all knew that.)
Photo Engineer said:I see a lot of lines in this particular scan though that confound my interpretation if any is really possible on-screen.
In this case, Alex, I think the main factor would be the backlighting, which causes the flower to separate nicely from the background, and then the fact that you're looking at a Polaroid with no enlargement or reproduction quality loss enhances the effect created by the lighting.
I used to generally agree with all that has been said above about Azo, contact printing and so forth until I took this one. The scan is from the test shot I did on Polaroid Type 664. Please don't try to judge the 3-D effect by this crummy scan, but believe me, on the actual Polaroid print, its there. I also did the full frame 4x5 shot on both Ilford FP4 and Efke 25. Not only that, but I also shot both films with two different lenses; my 12 inch 1940's vintage Commercial Ektar and a much newer Schneider 12 inch Xenar. I see the 3-D effect on all of the prints; polaroid, 4x5 contact, 8x10 enlargement, and 11x14 enlargement, all made on Kodak and Ilford multi-grade papers. So I dunno, the mileage varies greatly, but can be obtained seemingly irregardless of the materials in the mix. For me, that throws it all back to the lighting, contrast, and subject.
The reason I asked about the lens opening is that it is possible for a lens that is wider than the subject to see part of it that cannot be seen from a single point. A little ray tracing will show what I mean. I have only done the imaginary ray tracing, but you can imagine a ray that is tangential to a small round object entering the edge of the lens aperture. It will come from behind the surface you could see from the center of the lens. Such happens with binocular vision when the interocular distance is greater than the width of the object. Each eye sees part of the object that the other cannot see. The brain integrates the two images. It's just a thought.
Printed on a flat surface though, this type of imaging has (to my eye) been somewhat distorted. Like using a wide angle lens without barrel distortion in a way.
PE
David, Ron, you're both right. This was done with natural sunlight where the sun was very high and to the right, strongly backlit but with just a small amount of front lighting. And this is the crux of my point - getting the 3-D effect is not dependent on the paper, lens, film or any of that stuff.
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