Tricks of the eye and mind - 10 optical illusions everyone should see
It's fascinating how images and animations can have a way of tricking the eye and mind, and there are many different types of illusions out there. For instance: seeing movement when it's not really there, misperceiving differences in size, color or direction and being fooled in perception of depth. There are even illusions that make you see color in a black and white picture!
This article highlights 10 great optical illusions that everyone should experience. If an illusion gives you any feeling of physical discomfort, just look away or close your eyes. Enjoy and let yourself be fooled!
Seeing rotation that is not actually there
This illusion by B. Pinna is a fascinating trick of the eyes. When you sit still and look at the image nothing happens. But when you focus on the dot in the middle and move your head towards the image, or away from it, the two circles start rotating, and not only that, they do so in opposite directions.
Seeing color in a black and white image
Check this video for a truly amazing trick of your eyes. In the video you will see an image with inverted colors. You have to focus on the dot in the middle of the image, and be patient. After a while you will see the image turn into a normally colored photo. But the image you perceive as being normally colored is in reality completely black and white! Only when you change your focus point you will see the image being colorless.
Thinking two colors have different shades when they don't
The checker shadow illusion by E. H. Adelson is a so-called simultaneous contrast illusion, one of the most deceiving tricks out there. You think you are looking at two grey areas with clearly different shades. But.... they are not different at all, they are exactly the same shade of grey. If you like this illusion, then also check this other simultaneous contrast illusion with a grey bar.
A paper dragon following you with eyes and head
In this video you see a paper dragon that appears to be following you with its head and eyes. But the dragon is completely motionless. This really is an amazing depth trick and it has to do with the way the dragon's face is folded. If you'd like to make such a dragon (or other animal) yourself, there are several online printable images and tutorials on how to fold and glue. Don't forget to look at your folded animal without depth, so keep one eye closed.
Dots appearing to be moving around but they're not
When you look around in this image by Paul Nasca, the dots are moving! Well no, they're not, actually. This illusion is all about peripheral drift, or anomalous motion. The dots in the periphery of your focus field appear to be moving around. The effect of this kind of images is best when you view the image in a large size. Here's another example of a peripheral drift illusion, by Kitaoka Akiyoshi.
People looking like they are changing in size in the Ames room
Invented by A. Ames Jr. in 1934, the Ames room is another interesting depth trick. Look at this video. You think you are looking at a regular box room, but when people walk from one side to the other, they appear to be changing in size. This is because the room is not really a box room, and the person does not only walk to the side but also backwards or forwards. This is what an Ames room really looks like. The band Squeeze used the principle of the Ames room (as well as other visual tricks) in their interesting music video for the song Hourglass.
Dots disappearing when in fact they're still there
The lilac chaser illusion by J. Hinton is interesting for several reasons, but the most interesting thing about it are the disappearing dots. When you focus on the cross in the center of the image, the pink circles in the periphery slowly disappear until all you see is the grey background and the center cross. The illusion is immediately lost when you look away from the center.
A 2D image appearing to be 3D
An anamorphic illusion such as in this video is thinking that you are viewing a 3D object when in fact you're just looking at a flat 2D graphic with a skewed image of the object. Images like these have to be viewed from one particular view point. If you'd like to make an anamorphic illusion yourself, the above video also provides a tutorial. When you look at an anamorphic image lying on your own table, don't forget to close one eye.
Anamorphic illusions can be made on paper, but some people take it to another level and use streets or buildings as their canvas. There are several artists that create the most stunning 3D street art. One of these artists is Julian Beever, you really should take a look at his amazing work.
Lines appearing to not be parallel but they are
When you look at this parallel lines illusion you may think you're looking at nonparallel horizontal lines, but the lines are perfectly parallel. This effect was first discovered in 1898 and was called the Kindergarten illusion. In 1973 it was rediscovered on a wall of a Bristol café, therefore it's often referred to as the 'Café-wall illusion'.
Magnetic slopes, or....
This video shows another amazing eye trick where you get fooled with depth perception. Balls being rolled up a paper slope but not rolling back down. The whole thing appears to be a magnetic system. This trick has won Best Visual Illusion of the Year Contest in 2010. Another video with the same principle is this one. Watch the end to see it explained.