[argyllcms] Re: Image Engineering EX1 Spectroradiometer
- From: Graeme Gill <graeme@xxxxxxxxxxxxx>
- To: argyllcms@xxxxxxxxxxxxx
- Date: Thu, 20 Feb 2020 10:09:47 +1100
Cody Ranaldo wrote:
Hi,
Speaking of which, does anyone have some insight as to what is actually
done when a device is recertified/calibrated? Is this usually performed
through some kind of proprietary software offsets? I've always opened
these older devices hoping for some array of trim-pots to start fiddling
with, but never such luck, and for current i1pro devices I can't imagine
they're cracking them open and changing out resistors and the like.
for an instrument like the i1pro, it's all done by the calibration
tables stored into the instruments non-volatile memory.
At least three references would be needed for calibration :-
1) a wavelength reference, which is typically a light source
with obvious markers 2) an emissive reference spectrum for
calibrating absolute light levels and spectral uniformity
and 3) a reflective reference (or a reference reflection
measurement of the white tile) for doing the same for reflective
measurement.
You then end up with at least 3 tables. One gives you the raw
bin to wavelength conversion, one gives you the emissive
absolute and spectral intensity conversion, and one
has the reflective spectra of the white tile supplied
with the instrument.
There may be additional tables such as a stray light
compensation table which has information on how one
wavelength contaminates another, a reference spectrum
for the wavelength calibration LED etc.
Cheers,
Graeme Gill.
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