Graflex.org

[disemjg]

I just got this oddball device, which is an Ilex shutter with no optical elements, just a flat piece of glass at the front to keep your fingers out of the shutter. The back of the shutter is fitted with a large tube and a clamping screw, evidently to slide over some projection lens.

What was this for? My best guess is for some form of flash training, where an image was projected for a moment and you were supposed to be able to identify what the image had been. Something like aircraft identification training.

I'll ask Les to post some photos.

[glennfromwy]

My understanding is these things were used during the war to train pilots to instantly recognize enemy aircraft. It was placed on the lens of a slide or film strip projector.
I guess if you saw the thing flash a picture enough times, the images would stick to your brain. I have one I was using as a front mounted shutter but it's worn out and I don't think I can fix it any more.

[Dan Fromm]

When I was in high school I took a speed reading course that used a device called a tachistoscope to project letters, words, and short sentences for a very short period of time. It was basically a film strip projector (remember them?) with a shutter in front of its lens. This is basically Glenn's application.