[opendtv] Re: New Chips Improve Color TV Dramatically

At 12:59 PM +0100 6/29/04, Alan Roberts wrote:
>The transfer function (gamma curve) is vastly more important in colour
>rendering than is the choice of primaries. I've worked in this field on
>problems such as this for about 25 years now, and I never cease to be amazed
>at just how powerful the transfer curve is. Arguing about the primaries in
>non-linear systems is a real waste of breath, gamma is fully in control.


And

At 9:12 AM -0700 6/29/04, John Willkie wrote:
>If what "I heard" earlier this year at the Tech Retreat was correct (and it
>came from one of "authorities" in this area), the e-cinema/DCI folks are,
>for some unknown reason, proposing a wholly different gamut in their
>initiative, with little justification.
>
>Some said that was just another example of why the e-cinema initiative will
>never come to fruition.  I even heard that the e-cinema folks do not even
>understand that they are proposing a wholly new gamut and were due for a
>lecture by one or more of the "authorities."

This is a old and still raging debate. It is best characterized as a 
battle between the views of people who have come from two very 
different world of visual imaging...video and film.

Traditionally, video has not been about the accurate reproduction of 
imagery; it has been a compromise between what is possible in a cheap 
consumer receiver and what looks pleasing. The term "painting" is 
often used to describe what a camera operator does to produce 
pleasing images. the Video gamma was specifically designed to deal 
with issues that are no longer as critical as they were when crutches 
like "video setup" were created to deal with the inability of 
clamping amplifiers to deal with the confusion of sync and the lower 
range of the blacks in an image.

Gamma is quite different in a video system and a film system, yet 
both systems strive to improve performance in the non-linear ranges 
of their acquisition systems - i.e. the ability to perceive detail in 
the blacks and the whites at the extremes of the luminance ranges. 
Film is blessed with a logarithmic response in the luminance range. 
It captures MORE detail in the black and whites than it does in the 
mid ranges. This affords cinematographers and colorists with more 
latitude in the ability to pull out the details they need in the 
corrected images that we see. Electronic image capture tends to have 
a more linear response across the luminance range - video gamma was 
created to provide a more logarithmic response to extend the detail 
that can be presented in the blacks and whites, however, the entire 
range is crushed as a result, limiting the number of perceptual steps 
available to the observer. This obviously extends into the perception 
of color gamut as Alan suggests in his response.

The film guys are NEVER going to buy into the compromises that were 
imposed on the world of electronic imaging thanks to gamma. Rather, 
they are going to do everything possible to deliver the full range of 
luminance and color values that they are accustomed to capturing on 
film.

It should be OBVIOUS to any "vidiot" that this is not just some whim 
"without justification." All of the E-cinema cameras are now offering 
tools that allow the cameras to behave more like film acquisition 
systems, using terms like "Cine Gamma." What this really means is 
that the destructive video gamma curve need not be imposed during 
acquisition - the full response of the camera can be captured to 
disk, then the imagery can be color corrected prior to the 
introduction of video gamma for distribution to cheap TV displays.

What is equally important to the film industry is that the Cinema 
experience not be adulterated as we move to digital presentation.I 
can assure everyone on this list, that the Hollywood crowd has no 
intention of constraining a theater presentation system with the 
limits of video gamma and colorimetry. Fortunately, there is NO NEED 
TO DO SO. The digital projection systems already in use in theaters 
can deliver both improved luminance and color gamut performance when 
tuned properly for the task.

As Alan suggests, the place to start with any discussion of color 
gamut is with the luminance performance of the display. This is why 
an average computer monitor can reproduce "millions" of colors, while 
a video display can only reproduce thousands...

Fortunately these worlds are converging, and the old arguments of the 
"authorities" are growing stale.

May the CRT rest in peace...

Regards
Craig
 
 
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