More experiments with film; scanning and stereo!

Some time ago my Dad gave me a Kodak Stereo Camera as a novelty from one of his antique store forays. I’d wondered if it still worked, so I took it to the Lethbridge airshow. With lots of aircraft on static display, it would be a good place to try it out. It has some very limited settings for aperture and shutter speed, and focus is by guesswork, using a distance scale; the viewfinder is actually the square window between the lenses, just above the green bubble level.

Kodak Stereo Camera

Kodak Stereo Camera

Originally slide film would have been sent to Kodak and they would have cut and mounted the left and right images in cardboard to make them easy to use.  Keep this in mind if you have one of these cameras and would like to try it out… starting with slide film will save you a TON of time later on. All the unused film I have handy is 35mm for prints; not slides… had I known how much hassle I was about to cause myself I would have sprung for a roll of slide film for sure.

For starters, the images from each lens are almost square, and quite small. They are interleaved 3:1 on the negative, and that was the first hurdle. The photo lab couldn’t print or scan them because of the non-standard size… the tech tried, but the spacing didn’t match the standard mask sizes.

That left me on my own; I could go to a pro lab and explain to them what I wanted, and it would have cost a fortune in labour… or I could buy my own film scanner – but still have the same problems with needing non-standard image masks and having to realign every frame. What I ended up doing – photographing the negatives – was far more work, but the end results are (almost) worth it. If you get close enough to the screen and let your eyes cross the images below should fuse to a single 3D image!

Final result: A left+right image pair. Click for a larger size.

Final result: A left+right image pair. Click for a larger size.

After some failed experiments simply photographing the negatives against window light, I mounted a flash on one end of a 4 foot long bit of wood, my trusty K20D with a Tamron 70-300mm macro on the other end. One thing I had read about photographing negatives is that the orange cast of the negative can be best dealt with by gelling the lightsource to blue/cyan. I picked a strong blue gel from my freebie pack of Lee filters, and my first guess was pretty good (I think it’s #200 – Double C.T. Blue). I also put four layers of a white plastic bag in front of the flash as diffuser.

I mounted the negative at roughly the minimum focus distance. I used a folding cardboard slide holder taped against the bottom of a shoebox, with an oversized hole cut in the box. The flash was a few inches back from this, firing into the box to limit light spill. The camera was set to ISO 100 and f/11. Because of the spacing of the flash and camera I used some cheap eBay triggers; to keep the sync right I set it to 1/30 second shutter. The hotshoe trigger also gave me a handy mount for the flash.

The steps of transforming the negative to positive required some trial and error. These links should help:


http://www.velocityreviews.com/forums/t248544-digital-slr-as-slidenegative-scanner.html (scroll down to Dave Martindale’s post)


A negative, lit from behind with a blue gelled flash.

Starting from the image above, here are my steps using the GIMP (Photoshop should work too):

1. Switch to the color picker, and choose an area of neutral orange (the sprocket holes, for example) or something known to be grey (like a cargo plane).

2. Add a new layer using this new foreground color

3. Invert the new layer from orange-pink to blueish. I ended up editing this blue tint to be Red: 0, Blue:255, Green:175, after experimentation. A different filter on the flash will mean these values will change!

4. Set the new layer to ‘Overlay’ mode. This should improve the color range, but it’s still a negative image.

5. Merge the new layer down (you should have only one layer now)

6. Invert the layer; it won’t be quite right yet, but it should be close

7. Edit the curves for red, green and blue individually; I just selected the midpoint and dragged it up or down very slightly. Also edit the brightness and contrast to taste.

Hope this helps anyone looking to scan or copy old negatives with their digital camera. For the money a good flatbed scanner, with masks for 35mm film is going to save you a lot of time.


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