What is persistence of vision? How does it help us in seeing motion pictures?

 Persistence of vision is a phenomenon of the human eye wherin the image formed on the retina is retained by the brain for 1/16 th of a second. Motion Pictures can be seen by us due to this phenomenon. Motion pictures are shown at the speed of 24 or more pictures per second so that they merge together as a moving picture.

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Persistence of vision is the phenomenon of the eye by which an afterimage is thought to persist for approximately one twenty-fifth of a second on the retina .

Persistence of vision is still the accepted term for this phenomenon in the realm of cinema history and theory. In the early days of filminnovation, it was scientifically determined that a frame rate of less than 16 frames per second (frame/s) caused the mind to see flashing images. Audiences still interpret motion at rates as low as ten frames per second or slower (as in a flipbook), but the flicker caused by the shutter of a film projector is distracting below the 16-frame threshold.

Modern theatrical film runs at 24 frames a second. This is the case for both physical film and digital cinema systems.

It is important to distinguish between the frame rate and the flicker rate, which are not necessarily the same. In physical film systems, it is necessary to pull down the film frame, and this pulling-down needs to be obscured by a shutter to avoid the appearance of blurring; therefore, there needs to be at least one flicker per frame in film. To reduce the appearance of flicker, virtually all modern projector shutters are designed to add additional flicker periods, typically doubling the flicker rate to 48 Hz (single-bladed shutters make two rotations per frame – double-bladed shutters make one rotation per frame), which is less visible. (Some three-bladed projector shutters even triple it to 72 Hz.)

In digital film systems, the scan rate may be decoupled from the image update rate. In some systems, such as the Digital Light Processing (DLP) system, there is no flying spot or raster scan at all, so there is no flicker other than that generated by the temporal aliasing of the film image capture.

The new film system MaxiVision 48 films at 48 frames per second, which, according to film critic Roger Ebert, offers even a strobeless tracking shot past picket fences. The lack of strobe (as opposed to flicker) is due to the higher sampling rate of the camera relative to the speed of movement of the image across the film plane. This ultra-smooth imaging is called High motion.

 

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 Please follow the link given below:

https://www.meritnation.com/discuss/question/3442567/0/what-is-persistnece-of-vision

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it means that viewing of 20-25 images in a second as the human eye has capability of this
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            * The impression of an object seen by the eye persists on the retina, for 1 / 16 th of a second, even after the object is removed.
            * If another object is seen before this time, the impressions of the two merge to give us the sensation of continity.
            * This property of eye is called Persistence of Vision. 
 
               Hope this helped.
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