[argyllcms] Re: Next argyllcms release/i1pro2 + ColorMunki
- From: Graeme Gill <graeme@xxxxxxxxxxxxx>
- To: argyllcms@xxxxxxxxxxxxx
- Date: Tue, 24 Jul 2012 00:13:03 +1000
Ben Goren wrote:
> Anything new and exciting to report, or is it still looking like a marginal
> upgrade with not a
> whole lot to benefit those of us who own the original and already use Argyll?
I've been looking into the temperature stability of the i1pro2/Rev E, and have
made
a couple of interesting observations. One is that the Rev E (and also the
ColorMunki)
seems to have some sort of hardware/firmware temperature compensation to
counteract
the increase in dark noise with temperature. The good news is that this benefits
the Rev E in legacy mode, the bad news is that (at least on my particular
instrument)
it's not perfect, and the black reading in fact drops with increasing
temperature
(ie. it seems to be over compensating). The result seems to be better than
the behaviour of the previous revision i1pro's though.
An aspect of the ColorMunki and i1pro Rev E spectrometers that I've noticed
but not investigated or made use of up to now is that they have extra
measurement cells that are (presumably) optically shielded. This makes them
a candidate for tracking how the black noise is changing with temperature
for each reading, and automatically adjusting the black calibration to
compensate for the sensors temperature change since calibration. Some
experimenting indicates this can be quite effective:
The readings are the calibration black Y value in cd/m^2 in adaptive
mode (ie. integration time of about 4 seconds).
Temperature Rev A Rev E Rev E Rev E
Degrees C. No Comp. With Comp. Manufact. Driver
17 0.00 0.00 0.00 0.0
30 3.27 -1.01 0.00 0.897
Some experimentation indicates to me that the Manufacturers driver
makes use of the shielded cells to compensate for change with temperature,
but uses a simpler compensation model that doesn't perfectly track
how the sensor actually behaves (at least for my particular unit). It also
seems that the Manufacturers driver uses the same sort of scheme for
the ColorMunki, where (for my particular unit) it works somewhat better,
because the sensor seems to behave more straightforwardly, but a better
behaviour model still seems able to improve performance.
Temperature Munki Munki Munki
Degrees C. No Comp. With Comp. Manufact. Driver
18 0.00 0.00 0.00
30 -0.65 0.015 0.146
So in conclusion, the i1pro2/Rev E does hold the potential for
much improved dark calibration stability, and this should make
it much more usable in measuring displays. The ArgyllCMS driver
for the ColorMunki also holds potential for improvement in this
area too.
Graeme Gill.
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