[argyllcms] Re: Pioneer Kuro Plasma calibration with dispcal
- From: Graeme Gill <graeme@xxxxxxxxxxxxx>
- To: argyllcms@xxxxxxxxxxxxx
- Date: Thu, 16 Jan 2014 10:10:05 +1100
scott.janz@xxxxxxxxxxx wrote:
> Yes, dark current is as the name implies, a signal that can be measured in
> the
> dark. It's due to thermally generated electrons in the detector material and
> so
> it is sensitive to temperature. If the absolute response in the X Y Z
> measures
> that you saw with your dark test is consistent with your previous patch
> measured
> drift then you have isolated the problem. For the i1pro to minimize this type
> of
> error move the probe away from the plasma screen (which generates
> considerable
> heat) and allow to stabilize for 30-45 minutes. Run the calibration often
> (every
> 10-15 minutes) and use dark drift corrections in the software if available.
The i1pro Rev. A-D does suffer from thermal drift quite noticeably, wheras most
of the colorimeters have some form of thermal compensation (Thier L2F sensors
have inherent themal compensation). The i1pro2 & ColorMunmki spectro are also
much less sensitive to temperature drift, since they make use of extra
"covered cells" as a reference.
One way of minimizing the drift is to allow the whole measurement setup
to thermally stabilize before starting a calibration or profile. This
can take some time - maybe up to an hour. Moving the instrument away from
direct contact with the display may help this.
Doing regular instrument recalibrations is not so convenient, and
sometimes can't be done often enough - that's why expensive instruments
like the JETI specbos has a built in shutter, so that black cal.
is done automatically before each and every measurement.
Another workaround is to use the -Ib option. This works on the assumption
that the stability of the display black is better than the instrument.
Graeme Gill.
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