Re: [Frameworks] Quo Vadis Celluloid?

From: D Dawson <>
Date: Tue, 23 Aug 2011 09:43:42 -0500

If DLP projectors project 24 frames a second with no black. And film
projectors project 72 moments of image per second and 72 moments of black
per second -- could they not literally install a 3 bladed shutter that
travels in front of the image on a DLP before the lens? This physical
shutter would rotate fully once per 1/24th of a second, providing real black
three times per second, just like a film projector...

I am just thinking of ways to literally reproduce the actual flicker, not
doing it digitally... Nor am I encouraging digital projection to replace
film projection, just thinking here of some ideas.


On 8/23/11 4:08 AM, "Pip Chodorov" <> wrote:

> At 0:53 -0500 23/08/11, Fred Camper wrote:
>> But some of the technical points made about video don't sound right to
>> me, and I hope others with far more knowledge of the field than I have
>> can confirm this. Pip says video has no flicker. Can't DLP projectors
>> pretty well replicate film-like flicker? Can't they operate at 24 fps
>> if the material they are given is so encoded?
> I thought I'd look this up online, see if I can find an answer.
> I found comments like these:
> "1080P/24 material is flashed on the screen at
> 24Hz with no flicker (no black time)."
> "99.9% of consumer DLP projectors and all other
> consumer display technologies require 24fps
> source material to be flashed on the screen at a
> minimum of 48 Hz to prevent the unwatchable
> flicker issue from occurring"
> "The problem with old film projectors and most
> consumer Digital projectors is that they can only
> show an image half of the time, and the other
> half of the time one would be shown black. It's
> the 'black' time that causes the flicker. If
> there is no 'black' time there will be no
> flicker, no matter what the frame rate is. Think
> of the sunŠ its essentially 0 fps, and has no
> flicker. "
> "Since DLP displays are a continuous display
> technology, flicker-free display rates down to 24
> fps are possible without the need for temporal
> up-sampling."
> "according to Bob Williams, chief product
> architect and recent guest on my Home Theater
> Geeks podcast, this is exactly how digital-cinema
> projectors display movies, with no double or
> triple flashing as with film projectors."
> These comments somehow seem contradictory. I
> still didn't feel like I understand how these
> projectors work, so I looked them up in Wikipedia:
> No shutters, no flicker. It all depends on
> refresh rate. Many projectors have a spinning
> color wheel, which seems like an old-fashioned
> mechanical Rube Goldberg solution. The 3LCD uses
> prims and mirrors.
> It seems like any flicker would come only from
> the source material, but still there seems to be
> no black time onscreen. I guess you're right Fred
> that one could encode material so as to flicker,
> of course, but then the black would not be opaque
> but would be video black (dark grey). Maybe
> someone more proficient can "enlighten' us
> further...
> -Pip
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Received on Tue Aug 23 2011 - 07:44:16 CDT