This is topic Shutter flicker perception in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.
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Posted by Christopher Seo (Member # 7) on 07-24-2001, 03:58 AM:
I've noticed that shutter flicker increases dramatically when I look at a projected image out of a corner of my eye. Dark scenes (or dim screens) still won't show flicker, but bright scenes look terrible. I'm wondering whether this is a physiological or psychological phenomenon. Have any articles been written about the perceptibility of shutter flicker in general? I would think it ties in with the whole persistence-of-vision phenomenon.
Posted by John Anastasio (Member # 607) on 07-24-2001, 06:06 AM:
What you're describing is purely physiological. The central portion of your retina is much less sensitive to light than the outer portions. It's a tradeoff, because it's more densely packed with cells, so you see great detail with that area of your vision. It's also the location of the fovea, or "blindspot" where the optic nerve and blood supply enter the eye. One of the reasons that nature makes your peripheral vision more sensitive to changes in light values is that it's the area where you would first notice a moving object. Ever see something "out of the corner of your eye" and jump out of its way? It's a protective device to keep you from getting surprised by a hungry animal or maybe a Buick headed in your direction. Since the perception of flicker is related to your perception of brightness, flicker is more noticeable at the sides of your visual field. Anyone who's ever done any astronomy is aware of the effect, since it's much easier to see very faint objects at night by looking slightly to one side.
Posted by John Pytlak (Member # 331) on 07-24-2001, 06:44 AM:
John has it correct -- our peripheral vision is much more sensitive to movement or flicker, probably dating back to the days when prehistoric man was trying to keep from being the dinner of some hungry beast. It's easy to see the same phenomenon when looking at a television set or computer CRT display --- flicker is much more noticable when viewed "out of the corner of one's eye". I don't usually mind the flicker of 50 Hz. power or PAL television in Europe, but it is more visible when not looking directly at the display or light source.Here are some links to additional information:
http://scholar.lib.vt.edu/theses/available/etd-4229173039731191/unrestricted/flicker.p df
http://www.lboro.ac.uk/departments/hu/groups/viserg/9604all.htm
http://www.newi.ac.uk/jacksonk/public/graphics/PERCEP01.html
http://www.tech-notes.net/Archive/tech_notes_014.htm
http://home.pacbell.net/jim_sue/24_Frame.htm
http://www.assumption.edu/HTML/Academic/docs/CS80/m100over.html
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John P. Pytlak, Senior Technical Specialist
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Eastman Kodak Company
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