[argyllcms] Re: Pioneer Kuro Plasma calibration with dispcal
- From: Graeme Gill <graeme@xxxxxxxxxxxxx>
- To: argyllcms@xxxxxxxxxxxxx
- Date: Mon, 13 Jan 2014 10:46:25 +1100
Fatcat wrote:
> I'm having a big trouble calibrating the Kuro PDP-LX5090H plasma with
> dispcal(gui) and
> i1 Pro (ES-1000) spectrometer. The problem is that the results are extremely
> inconsistent
> even when the profile quality is set to "high" and the speed is set to the
> slowest.
Hi,
I'm not sure quite what you mean by "speed set to slowest". Certainly
you get more accurate low light readings when the instrument uses adaptive
measurement mode.
Plasmas's have a number of peculiarities, ABL being one of the major ones,
which is usually dealt with by keeping the test square small enough not
to trip it. (ie. 10% area).
A second aspect is that, like CRT's, they are refresh display, refreshing their
phosphor pixels at regular intervals.
For instruments that support it (ie. the i1 display pro), it helps measurement
consistency to run in refresh measurement mode. I didn't add such a mode to the
i1pro
driver though, because it proved to be ineffective - the timing resolution is
insufficient
to synchronize the measurement with the refresh rate accurately enough, and
typically
the i1pro integration time is long enough to make the refresh rate error
irrelevant.
The third aspect is that Plasma's have notoriously poor level resolution, and
this
is typically covered up by extensive amounts of spatial and temporal dithering.
Combine
this with a physically large display = quite large pixels + the instrument
aperture, and
you have a recipe for reading inconsistency.
Rather than continue to use dispcal and/or dispread over and over, I'd recommend
just getting to the bottom of the reading consistency issue first. Once that is
under control, the other tools should work as per normal.
The tools I'd recommend for that are "dispwin -m" to display 100%, 75%, 50%,
25%, 12.5%
& 0% grey, and "spotread -V" to check reading to reading consistency +
standard deviation. You use the interactive "r" command to set a reference, and
then you can check the delta E + statistics for subsequent readings. If you're
getting
delta E's > 1, then this points to a consistency issue of either the display
and/or
the measurement.
You need to figure out where this is happening or where it is worst - near
white ?
In the middle ? Near black ?
As others replies have suggested, one thing you might try is to move the
instrument away from the display by a small distance, say 5 - 10 cm., and
measure in a darkened room.
I note in the that in your trace the black reading is extremely inconsistent.
The initial measurement was XYZ 0.1559 0.1159 0.1118, while at
the end of the trace it's XYZ 0.789801 0.641749 0.430189. This doesn't seem
correct for a Plasma display - they generally have good blacks < 0.1 cd/m^2.
The the profile black is XYZ 0.073409 0.062720 0.039863. What's
going on with the black readings ?
Yes, try filling the rest of the screen with black to see if this is part
of the problem.
Graeme Gill.
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