This copied from a deliberation that Persistence of vision not related to motion on screen. In the 1800s, Roget or someone like him found that red has shorter persistence of vision than other colours. This is not mentioned anywhere else on the internet.: There is no motion on the screen, just a succession of still images. If there were persistence of these images in the eye of the viewer, figures on the screen would pile up, one on top of the other, resulting in a kind of chronophotographic display. persistence (i.e. the after-image) is necessary in the cinema, in order to ensure that we are unaware of the blank (dark) screen which occurs between the projection of each image; and that if it were not for this persistence,the result would appear to flicker. Firstly, motion picture systems exist which do not have a blank screen between images; e.g. Steenbeck viewing machines, in which a prism block mixes one image into the next. So even if persistence were necessary for conventional projection with an intermittent shutter projector, the existence of systems that do not have blanking periods means that it can hardly be considered important to our understanding of how we perceive apparent motion in motion pictures. What actually happens after a bright image is removed is that we see a succession of after-images, some positive and some negative. Obviously, the negative after-images are irrelevant; we do not perceive negative images when we look at motion pictures. More importantly, the first after-image, which is positive, appears some 50 milliseconds after the image ceases. In that period of time, not one but at least two screen images (at 48 flashes per second; that is, 24 frames per second with a two-bladed shutter) would have been viewed. Put simply, the first after-image of a film frame is not actually perceived until after at least one following frame has been projected. in Mr. Proszinskis opinion, is altogether insignificant, and may be put out of the reckoning as far as the phenomenon of the moving picture is concerned. ..In his opinion the continuity of the cinematographic vision is due to no such physiological phenomenon as persistence, but is purely an illusion. It is psychological, and not physiological at all.
Posted on: Wed, 06 Nov 2013 23:15:48 +0000
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