Persistence of vision
The modern cinemas use technology to produce an optical illusion and to deceive our brains. When we observed a photogram of the film the eye and the brain retain it during a fraction of second. To this phenomenon persistence of vision is called to him. If at a moment an object in front of the eyes is placed and after certain interval it retires suddenly, the eye has the sensation to continue seeing the object during a very short time, even though this one no longer is in front of the eye; that is to say, the vision of the object persists. This phenomenon is due, apparently, to that when arriving the light at the retina and being sent the corresponding nervous signal to the brain, has been certain time so that the signal is processed, so to speak.
The brain retains the illumination impression during an interval of around 0,1 seg after the light source has retired. This phenomenon implies the following thing: assume that two events in a time interval smaller to 0,1 seg happen alternatively, the eye perceives the first event, but when happening the second, the effect of first still persists in the brain, reason why account does not occur of which the second event happened. This fact has been applied to create illusions of apparent movements as the cinematograph and the television. The base of these illusions resides in the fact that if two separated fixed images in at least 0,1 seg appear to each other then the eye has the sensation of which it happens movement. In fact, when to the visual system a series of fixed images appears to him quickly, these are not seen of discontinuous way; is that “the stuffed” brain, so to speak, the lagoons between the images and imagines that it is seeing a continuous sprite.
In the films every second appears a succession of fixed photographies (the pictures) at a speed of 24 pictures. On TV also one appears sucesió of fixed images at the rate of 25 to 30 pictures p/seg.