Re: Monitor calibration/profiling for video applications
Re: Monitor calibration/profiling for video applications
- Subject: Re: Monitor calibration/profiling for video applications
- From: THOMAS A LIANZA <email@hidden>
- Date: Thu, 16 Aug 2012 07:07:27 -0400
- Thread-topic: Monitor calibration/profiling for video applications
Hi to all,
Graeme's comments, as usual, are spot on. I work with the ICC and have
worked with the Academy on issues of color management, so I think that I can
speak with experience in both camps. The greatest differences between the
film workflows and graphic arts workflows fall in areas of white point
assumptions and total system dynamic range. Another area that is also
common is the need to maintain a subjective "look and feel" across multiple
media.
The largest population of users of serious ICC technology are "by the
numbers" guys. A great deal of effort is spent making output devices behave
in a more or less standard manner with definitions of primary, secondary
colors and tone response curves. The device links that Graeme refers to are
tables that resolve predicted color differences between device and an
assumed standard input in device coordinates. This is exactly the same as
the technology described by the troll you spoke with.
The motion picture industry tends to be driven by perceptual intent.
Certainly, in video situations, real time editing is done and the ASC
(cinematographers) have a standard set of controls that are simple, but
defined to convey the intent of the director or cinematographer to the next
stage of production.
From a display calibration standpoint, there are two very important factors
in video and mp applications that generally don't exist in ICC applications.
First there are two distinct standards that are generally used in these
applications: Rec. 709 and DCI-P3. These are two prevailing output
assumptions. Displays used in video applications often use a Serial Data
Interface (SDI) which guarantees that each display receives exactly the same
data. This means that these displays must contain hardware calibration
capabilities inside the display. This same requirement is developing for
video walls and ON-set applications where multiple folks have to see the
same image, but are not physical proximity. This means that the calibration
hardware transform is built into the display. Many high end displays have
this capability and you will soon see it in low cost LCD displays as well.
These transform engines in the display generally are 14+bits and use either
table lut or lut-matrix architectures to transform the native display
primaries to the required working space requirements. These are exactly
analogous to the Device Link that Graeme refers to.
Modern display calibration is far more common between video, motion picture
and graphic arts than ever before. The physical difference between displays
is driven more by the physics of the display than any color management
style. The motion picture applications push towards very wide dynamic range
and the graphic arts applications push towards lower contrast ratios. This
difference is aimed primarily at the differences in destination media.
There certainly is a lot of hubris in the Video and Motion Picture camp, but
in the end, the approaches to get to the final result are far more common
than different.
Regards,
Tom Lianza
On 8/15/12 10:30 PM, "Graeme Gill" <email@hidden> wrote:
> Dennis Dunbar wrote:
>> Is anyone else familiar with the different approaches to color management?
>> And if so could you help
>> clear up the fog for me? (Do they really have something there, or are they
>> just blowing smoke?)
>
> Mostly blowing smoke :-) Typically Video and Film are aiming at a very
> specific sub set of general color management: Emulation of a particular
> standard. The print equivalent is side by side proofing. So most
> of the talk is about calibration (ie. making a display device
> behave in a specified way). ICC profiling is more general and
> flexible, and provides a mechanism for actually achieving the color
> management sub set desired by video or film.
>
> Another key difference between Video/Film and general color management
> is the mechanics used to transform color. Computer systems can use
> software, which is very flexible but not necessarily real time.
> Video/Film often have either very simple hardware controls (ie.
> "brightness" and "contrast" knobs. "RGBCMY" primary controls that don't
> work so well, per channel curves etc.) or the high end actually has
> hardware capable of per channel, matrix and 3D cLUT transforms (ie.
> all the machinery ICC profiles use). What's loaded into the 3D cLUT is
> the equivalent of a device link. (Note though that real time computer
> color CMM's can be implemented using GPU's.)
>
> Graeme Gill.
>
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