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Well, this time as well as looking at the newest techno toys, I suggested we visit the adjoining "antiques mall", which is really a collection of small antique stalls under one roof. I had at the back of my mind the idea to find an old Queen Anne style tripod table support, that I wanted to marry up to a 1976 disk drive platter which I'd always wanted to make into a table. However what I actually found that piqued my interest was...
this, which turned out to be an old Victorian stereoscope. I'd never actually seen one of these before - my exposure to stereo photographs had just been to red/green superimposed images or the nasty lenticular views they used to do for 3D postcards. This antique stereoscope quite blew me away! - the quality of the views was excellent and they were in full colour! (Admittedly they were hand-coloured black and white photographs I was looking at, but the principle was obvious - a different view for each eye, no red-green headaches).
I thought to myself, well, if the Victorians could do something as great as this all those years ago, Twentieth Century Scotsman should be able to at least duplicate it if not do better. I resolved to make myself a stereo viewer of my own, though at the time I had a very naive idea of how the optics worked. I would have bought the antique viewer on the stand, but for $150 it seemed excessive just to look at stereo views; I was sure I could build something better for less.
How little I knew then... but I learned fast - after an hour or two of surfing and searching I had found a tremendous wealth of info on the net on this subject. In one page I found a diagram of the lenses used in a stereoscope. At first sight they seemed strange - they were built from a large magnifying glass type lens, which was cut in half, but the halves were swapped over:
I didn't really follow how it worked at first, but I can copy a design as well as the next monkey, so I decided to make a viewer from a magnifying glass. I didn't have any tools with which to saw up glass lenses, but fortunately I had a large Fresnel lens that belonged to Anne's mother which she'd used for reading the very small print in the OED. I carefully sawed it down the middle, and cut off a strip on either side of the center which I then swapped over. Who'd a' thunk it - it worked first time! I finished off trimming the lenses, then make a proper pair of 3D specs to mount them in. (That was fun: I took a pair of red/green specs I had, and traced their outline on cardboard. Worked pretty well. Cardboard and scissors and clear tape - nothing fancy needed)
Armed with my brilliantly designed Fresnel stereo glasses I could now browse the stereo pairs on the web. What a wealth of pictures there were to look at - shame they were somewhat fuzzy though - the Fresnel lenses tended to make images look a little cloudy. I thought I had been smart using a Fresnel when the lenses I saw on the net were either chunky large glass ones or cheap plastic ones which I thought couldn't possibly magnify very well, but later I was to find out otherwise - it seems there have been major developments in the refractive index values of plastics since I last looked at them, and in fact polycarbonates are now being used for prescription glasses. Some lightweight materials are actually better than glass.
It was now that I had my own viewer that I started to understand how the viewer worked: it is a combination of two effects - first their is a small degree of magnification whose only purpose appears to be to allow the eyes to view the pictures while focused at infinity (this apparently is more natural to the eye when the brain perceives the photographed scene to be in the distance); then there is a degree of prismatic bending which adjusts the natural angle of the eye to effectively make you cross-eyed without the need to actually cross your eyes. This way the left-hand image is moved right a little, while the right-hand image is moved left, and both images meet in the middle of your brain where they're put together into 3D.
When I bought some decent glasses from Reel 3D (who I found on the web), I received their catalogue and in it I found someone was manufacturing kits for making your own replica antique stereoscope. I bought one (that's another tale) and was very very chuffed with myself when I found that my home-made mounted cards worked perfectly - in fact better than the antique cards I had seen.
The conclusion of this tale is that 6 weeks after first seeing the antique Holmes Stereoscope (named after Oliver Wendel Holmes, the famous Chief Justice of the Supreme Court) we had another trip to San Antonio, for the Labor Day holiday, and so we returned to the Antiques Mall. I was surprised and delighted to find that the original viewer was still on sale. This time I determined to buy it (although I had by now built a good replica of my own) for sentimental value - this was after all the actual stereoscope that had launched me into this enjoyable and educational hobby. And since it hadn't sold in all those weeks I was able to haggle the price down to a hundred dollars, which is probably about right - I've seen a similar one but in good condition and with case on the net for over $300. Well, it turns out that the old glass lenses are better than the modern plastic lenses, and although I like the reproduction viewer from Reel 3D, I now use the antique one almost exclusively. If I were a philistine I'd take the lenses from the antique viewer (mid 1880's is out best guess) and put them in the modern frame, but that would be a cruel fate for a fine antique which survived this long, so I will preserve it and look around for another source of glass lenses - perhaps I can find a set of the superb achromatic ones that Alan Lewis wrote about above.