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本帖最後由 r32 於 2011-4-2 09:31 編輯
http://forums.highdefdigest.com/ ... -frame-rate-34.html
Why 144fps is used in 3-D Cinemas around the world
In commercial 3-D cinemas, a 48Hz 3-D native source will always be flashed on the screen at a minimum of 144fps since engineers have discovered that when 96Hz is used a flicker is seen on the screen by 50% of the people. If the 3-D image is flashed on the screen at 120HZ by a LCOS or DLP Projector most people will not see the flicker but instead experience unnatural 6:4 pulldown (3:2 pulldown judder for each eye). So all 3-D Cinemas flash the 3-D image on the screen at a minimum of 144fps to completely eliminate flicker and 3:2 pulldown issues.
Flat panel 3-D plasma screens are much brighter compared to front projectors, do to the brighter screen on a plasma screen some people have seen flicker at 120HZ with 3:2 pulldown issues. Hopefully future 3-D plasma screens will operate at 144HZ or 192HZ to offer flicker free 3-D performance with no 3:2 pulldown for each eye. DLP and Plasma displays with their fast response times are ideal for 3-D. Some other technologies might take several years to offer good quality 3-D. LCD technology at 240Hz inserts black frames into the 3-D image which results in 60Hz for each eye using 3:2 pulldown. Perhaps future LCD screens with true native 480Hz refresh rates might be able to do 3-D without 3:2 pulldown judder for each eye.
The following are some interesting quotes from pages 46 and 47 of the February 2011 Widescreen Review magazine
“Typically when you see them in the theater they’re operating at 144 Hz. The reason for that? We’re back to 24p, which is the actual framerate that the content resides in, and 144 Hz is what we refer to as triple-flash. So you’re seeing the left eye triple-flash, so 24 times 3 equals 72, plus the right eye triple-flash, 24 times 3 equals 72, so combine 72 left eye and 72 right eye, the projector operates at 144 Hz. A modulator that sits in front of the projector – and it’s actually operating synchronized with that so it’s switching polarization realtime – so that you’re seeing left and right eye information sequentially. And it allows you to use passive glasses, but it requires a silver screen. The general feedback from most users is that they find passive glasses the most comfortable, because they’re lighter and they physically don’t switch. There’s no power to them. You don’t have to worry about ‘are the glasses on?’ There’s no emitters. There’s no challenges like that. In a professional, non-consumer world, medical imaging technicians will only use passive glasses. Primarily because when they’re doing research-oriented work, they find that they are actually over a period of time sensitive to the switching of the glasses, where with passive they don’t see that.”
“The advantage of a single projector that can operate at 144 Hz, basically, is that you can do any of those technologies. We could do passive, we could do active, or we could do passive/active.”
“Today, if you’ve got a Blu-ray Disc player, most of them, when operating in 3-D mode at full resolution, it outputs 24p. Effectively, in that timeframe you’re getting left-eye information and right-eye in a shorter time interval – effectively 48 Hz. So left eye and right-eye combined at 24p. We triple-flash that so the projector actually operating at 144 Hz. Why? Because if we only double flash, 48 and 48, you get 96, you literally start to see flicker. Again, you get down to the dynamics of the human eye. Fifty percent of people at 96 Hz wouldn’t see flicker. Fifty percent would see flicker. When you up it to 120 Hz, basically nobody sees it. At 144 Hz, for sure, nobody sees it. But if we stayed at 120 Hz, you’d have to basically get back to some derivative of 3-2 pulldown. If you go 144 Hz, it’s natural – triple flash. And the beauty of active is that we use exactly the same screen for 2D as 3D. So there’s no need to change the screen.”
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發表於 2011-4-2 09:23
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