Thursday, April 7, 2011

Persistence of Vision

While driving back home with Navaneeth , we struck a conversation on  Film ..not the movies but the actual Film reel or tape ... our conversation was carried on to film frame rates like  24 , 25 , 30  etc ..and from there Navaneeth started to break  these things down to simpler form ..  so  before getting in to 24 25 30 Fps .. he asked me to read up on PERSISTENCE OF VISION..which I have been  doing for about some time now ..so I thought I like to share that with the rest of  you ..

How is the Illusion of  movement is achieved when none is present ? In other words   how do we see a seq of images and feel that  its movement ?

This marvelous phenomenon is known as the persistence of vision and it is through this that we experience moving images made up of frames on a film strip. The secret of this illusion is be found in the remarkable capability of a part of the human eye, the retina, of momentarily retaining any image it receives.
Imagine, if you will, a light being shone into the eye only briefly and appearing on the retina as a bright spot. This bright image would appear to remain for a brief period even after the light had been turned off. It’s this slight period of retention or delay that allows for separate sequential images, if seen in quick succession, to appear as a moving image, and it’s upon this principle that film and video projection works.

1765 by the Frenchman, Chevalier D’Arcy, that it was established that this retention period was approximately one-tenth of a second. The early optical devices that were developed and began to appear in the first half of the nineteenth century clearly demonstrated this effect. What started out as serious scientific investigation soon found a practical application for entertainment through the use of such devices as the thaumatrope, the zoetrope, Joseph Plateau’s phenakistoscope and Emile Reynaud’s praxinoscope. Variations of these quickly began to appear as popular parlor toys in the homes of the upper classes throughout Europe. 


Post a Comment


Twitter Delicious Facebook Digg Stumbleupon Favorites More