Seeing
Optical phenomena
Discover how your eye reacts when you see optical phenomena. You will be amazed at the way the pictures seem to move of their own accord or you are seeing things which your neigbour does not...
Café wall effect
- wedge-shaped or square? -
The graphic below is interactive:
Push the square with the aid of the yellow dot (below right) inside the bar.
What happens?
This phenomenon was first discovered on the wall of a café in Bristol which was covered with black and white tiles. When you look at the café wall you see the “grouting”. This makes the tiles appear wedge-shaped. In actual fact they are parallel and the same size. How can the effect be explained?
Our eyes do not have the resolution capacity to differentiate the border between a light and a dark tile as a separate object. Our brain interprets the fact that the space cannot clearly be attributed to a light or dark tile and assigns it as part of the adjoining tile.This is how impressions of wedge-shaped tiles are formed.
Jerry Andrus Effect
Why do motionless objects suddenly seem to move? Try it out for yourself!
The graphic below is interactive:
Start the following animation. Start the spiral with the yellow arrow, stop it with the square. Now look at the centre of the spiral for 30 seconds and then at a motionless object, e.g. a glass. Doesn’t the glass suddenly seem to move?
What we have here are the so-called after images of movements or the waterfall effect. If we look at a waterfall or any other steady movement for a while and then look at stationary images, for a short time the latter seem to be moving in the opposite direction.
