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:
http://en.wikipedia.org/wiki/Digital_Light_Processing
http://en.wikipedia.org/wiki/3LCD
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 - 02:09:01 CDT
