[opendtv] Re: RGB mania ('translated' for Prin)
- From: "Manfredi, Albert E" <albert.e.manfredi@xxxxxxxxxx>
- To: "OpenDTV (E-mail)" <opendtv@xxxxxxxxxxxxx>
- Date: Fri, 14 Jan 2005 18:31:08 -0500
Prinyar Boon wrote, with John Golisis' able
assistance:
> At the display end, a conventional TV [not
> a broadcast monitor] - will allow the small
> area luminance level to reach say 450cd/m2.
> However the large area light output will be
> limited to say 120cd/m2. So a tellie - as
> the ability to have a stab at reproducing
> specular highlights.....and does this by the
> miracle of beam current limiting. It also
> manges to interpret small areas of code 235
> as specular. This is probably a good thing.
This is a fascinating thread. If I understand
what you're saying, a normal TV transmission
assigns Y values of, say, 235, both to large
areas of normal white and to tiny highlights
which should be super-white. And because CRTs
react to Y values in strange ways, they will
naturally blast a very powerful beam on a
tiny area identified as Y 235, to render the
specular highlight expected there, even
without having been told specifically that
this tiny area was actually brighter than
the large areas marked Y 235.
So I'm trying to see how an LCD would react
to this, to see if I can understand why it
was so much harder to adjust my LCD than it
is to adjust a CRT TV.
An LCD would paint the specular highlights
with the same intensity as the larger normal
white regions. So perhaps if one sets the
screen to look right for specular highlights,
the effect is that all the white or brighter
regions of the image look too pushed. It's
especially noticeable on b&w images.
Which makes one want to back off on the
"contrast" control (i.e. white level), which
in turn causes the darker parts of the
scene to fade to black too fast.
If this reasoning is about right, it would
describe what I was seeing. My reaction was
to back off on the "contrast" and turn up
the "brightness" (i.e. black level), to
bring up the darker parts of the image.
Another thing I noticed is that the darkness
effect was more pronounced in material I
had recorded. Using the 3-hour recording
mode on my DVDR, instead of the 6-hour mode,
improved matters. I wonder if the 3-hour
mode might assign more bits to Y, which
would explain the difference.
> However this combination/mixed melange of
> display characteristics in the field just
> makes things even worse, we have NO
> chance of achieving a controlled transfer
> between broadcast monitoring and home
> viewing.
Seems to me that the newer types of display
could incorporate whatever smarts are
needed to post-process the incoming data
to emulate the CRT response. If they need
scalers and deinterlacers anyway, they
already have built-in smarts.
Bert
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