Optical illusions

If your eyes were
adjustable like

There are many possible optical illusions. Some are just a trick to fool the eye, or a gimmick in the filmindustry. But art has also found them usefull sometimes, fx Escher, Magritte, Dali...

However, all illusions I've seen did have one irritating drawback. Each time I was left with the impression that the illusion was an effect of the picture, not the eye. That is actually an extra illusion by itself. Optical illusions is caused by the optics itself (=eye+brain), no picture is required. In other words, you may create an optical illusion merely by manipulating your own eyes.

If your eyes were adjustable like television...

Vision comes in more than one variation. The local vision is your eyes, a telescope is better suited for things faraway but still visible. For things so far away that they are no longer visible, there is television. And here the image is adjustable in several ways: brightness, colourbalance, coloursaturation.

You may even shift channel. Quite a difference to the naked eye, that portraits reality directly without any adjustments or filters. Or what..? Actually the eye may be adjusted as is it was tv. Here are some simple experiments that anyone may try:

Adjust colour

Maybe you have a pair of red-green glasses, or something similar? Put them on and look at a bright but indirect source of light. After a minute, close both eyes and remove the glasses. Now you may observe reality with 'new' eyes: Use your left eye, or the right eye. But only one eye at the same time. Now, what colours does reality really have..?

Adjust brightness

The experiment is somewhat similar to adjusting colours, but much easier. This time glasses are not neccesary. Close one eye (and use your hand to block all light). Let the other eye look at something bright (not blindingly bright, as the idea is to saturate the eye, not overwhelm it.)...

Wait a minute and then close both eyes. Open one eye, left or right, but only one eye at the same time. Now, how bright (or dark) is reality really..?

Adjust colour-saturation

If brightness and colour-balance may be adjusted, how about colour-saturation? Quite simple - observe the same view in the middle of the day - and at night. They dont look the same, but the difference is only partially caused by different levels of brightness. Colourvision depends on sufficient brightness, and nighttimes offer very little light. Objects becomes not only darker but also much more grey. So, how much colour does an object really contain..?

These examples are not the only ways to reprogram your eyes, only the simplest. Try some experiments yourself...

Shift channel..?

If the eye is comparable to television, how about shifting the channel and look at something completely different..? But of course that's asking for too much? And yet, the solution is quite close: Close both eyes, and relax. Fall asleep. Start dreaming...

Mads Dam, dec 2004


The red/green-system was a popular trick in the 50'ies, and several 3d-movies were made. Even Hitchcock tried it once (Dial M for murder, 1953), but today the film is probably only available in a flat version. Hitchcock wasn't too fond of this new gimmick anyway, and used it only sparingly...

Red/green glasses is a simple device to create 3D effects. A green and a red version is superimposed on the same screen, but the coloured glasses separates them again. Each eye is thereby offered its own version, and then the brain (as it usually does) fuses the two into one. This system has a severe limitation though, as the result is only a greyscale-image. To get spatial depth you pay with colour depth.