In World War II, one method used to help air-crew gunners speed up their aircraft identification skills was to flash photographs on a screen of the planes they had to recognize. One device used for this purpose was called a tachistoscope (ta kis' tuh scope). Instructors could vary the duration of the images being flashed on the screen. At times the images would be flashed for just a few hundredths of a second. Blink and you miss it.

Funny things began to happen. When the gunners were in darkened rooms during this training, their eyes became dark adapted. It was found that many of them were holding on to the split-second images after the images were no longer on the screen. With dark adapted eyes, the images could be retained for a few seconds.

A study was set up to see just what could be done with these retained images. The images were positives instead of the more familiar negative images you get if you stare fixedly for a few seconds at a picture or scene, then look away. Some subjects got so good at the process that after seeing a very short duration image of a page in a book, they could then read the page, from somewhere inside their heads.

The above information was told to me by Mr. Ray Elkin, of Elkin Jewelers in West Lafayette, Indiana in 1962.

The fact that some of the study participants could acquire a readable image of a whole book page suggests that their peripheral vision happened to be, or became, more acute than that normally found in the general population. This form of retained visual images may not be accomplished with the same process as is done by people who have what is called photographic memory. I didn't think to ask Mr. Elkin, but the idea of long term storage and recall of the images did not come up.

I have not pursued the issue of long term storage.

I didn't have access to a tachistoscope but decided to try an alternate technique for seeing the retained images. Dark adaptation seemed to be a prerequisite for the short term image retention. One way to dark adapt you eyes is to close them. Its not the same as being in a dark room but one can get a similar effect. Then comes the tachistoscope emulation. Rapidly open and close your eyes (like a blink, in reverse). This is not unlike exposing film in a camera. The first few hundred times you try this, you'll probably get blurred images because your eyeballs aren't yet convinced to hold still during the exposure. The images will be there but doubled, usually vertically. Keep trying! It's also wise to make sure that nobody is watching you.

After a month or so of your covert camera work you should find that your eyeballs begin to cooperate (the process might be called the steely eye)and images of big things with good contrast start to hang on. Big letters on billboards and soft drink machines make good targets.

With lots of work, assuming you haven't been put away, you should find that text in books show up in blurry fashion, unreadable, but recognizable as fuzzy text. Large print documents may bring more rewarding results. As time goes on the acuity should improve to the point of readability.

It may be that that tachistoscope simulation near the top of this page, if viewed in a darkened environment, may provide a usable indicator of the process being discussed.

You can cheat, or take a short cut if you please, by using a camera strobe flash in a dark room. Hold the flash unit above or to the side of your head and aim it at an outstretched arm. You'll see a bright image of your arm that does not immediately fade away. The image may last for two or three seconds. If you lower your arm while the image is still active you can have your own spooky show.

From: porcupine.egg...
To: rsf1...
Subject: photographic memory
Date: Sat, 24 Jul 2004 19:54:54 +0000

I have figured out a better way to simulate a tachistoscope than a camera.
A camera would waste film. Just go into a bathroom and quickly turn the light
on and off. After the first 10 minutes of the bathroom lights idea, I could read
a crystal clear cover of a book.

This technique looks worth pursuing. Two special notes:

(1) The "camera strobe flash" mentioned above was strictly that. A separate flash-unit or
empty camera was implied!

(2) It would behoove the experimenter to use a light-tight room, especially at night.
No sense agitating family members, or convincing neighbors that you've "lost it".