Re: profiling monitor range
Re: profiling monitor range
- Subject: Re: profiling monitor range
- From: Graeme Gill <email@hidden>
- Date: Tue, 20 Jun 2006 00:17:35 +1000
email@hidden wrote:
On Jun 19, 2006, at 12:05 AM, Graeme Gill wrote:
Unfortunately, the CRT calibration routines can not accurately
describe the slope of multiple contrasts in the LCD/TFT.
Care to translate that statement into something meaningful ?
What is "slope of multiple contrasts" ?
Sure. Whether LCD or TFT, the technology does not exhibit a single
curve (or more accurately stated, straight line) over the entire
brightness range, as the analog CRT device might.
Straight line ? Since when has any display device
exhibited such native behaviour ?
> Instead, one finds
various issues in the highlight, midtone, and shadow regions which
force the calibration software to manage not only the independent
issues, but then also the resulting approximation of a single curve.
The failures of the system in producing a good black and smooth
transitions through the shadow region are especially difficult to
overcome . . . unless sophisticated LUT functions can be employed.
You are making lots of assumptions about such calibration systems,
that are not universally true. There doesn't have to be a "single curve" :-
different systems can and do use a variety of functions to match
real world device behaviour. Only the most simplistic systems will
assume a power curve. A general device model will model a CRT and
LCD in a similar fashion, and to a similar degree of accuracy.
Sorry, I don't see and particular connection between the calibration
target luminance curve (be it a power curve, a power curve
with a flat region near black, or an L* shaped curve), and
the neutrality of the resulting curve for equal valued RGB input.
They are orthogonal axes, hence independent.
Let's assume that uniform perceptual RGB contrast is a gamma of 2.46,
and is approximately equal to uniform L contrast. Let's further assume
that with a* and b* equal to 0 each, that the perception is absolute
neutrality.
If that is the case, and if we are trying to dig contrast out of the
flat panel shadows, while constraining contrast in other areas, then
the best chance of a monitor matching a printed piece (and the
correlating gradations) would be to delicately manage the various
display issues in a way that is transparent to the end user (no pun
intended).
In simple terms, flat panel calibration is extremely difficult, by
comparison to CRT calibration -
Extremely difficult ? I hardly think so. A general approach deals
with each device just as easily. It seems to me you are building up
a straw man in order to promote a particular product.
> and matching a flat panel to a printed
piece (when judged by neutrality and contrast) is one of the hardest
functions to accomplish. basICColor display has done an excellent job
of the calibration and profiling of flat panel displays.
You certainly are a fan.
Graeme Gill.
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