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Author Topic: Shutter flicker perception Christopher Seo Jedi Master Film Handler Posts: 530 From: Los Angeles, CA Registered: Jun 99 posted 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.  |  IP: Logged John Anastasio Master Film Handler Posts: 325 From: Trenton, NJ, USA Registered: Sep 2000 posted 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.  |  IP: Logged John Pytlak Film God Posts: 9987 From: Rochester, NY 14650-1922 Registered: Jan 2000 posted 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 ------------------ John P. Pytlak, Senior Technical Specialist Worldwide Technical Services, Entertainment Imaging Eastman Kodak Company Research Labs, Building 69, Room 7419 Rochester, New York, 14650-1922 USA Tel: 716-477-5325 Cell: 716-781-4036 Fax: 716-722-7243 E-Mail: john.pytlak@kodak.com Web site: http://www.kodak.com/go/motion  |  IP: Logged

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