[argyllcms] Re: Poor Man's Reference Light Source (was: ColorMunki measurement drift)
- From: Roger Breton <graxx@xxxxxxxxxxxx>
- To: argyllcms@xxxxxxxxxxxxx
- Date: Sat, 02 Oct 2010 14:28:10 -0400
Jurgen,
I would like to go along with your idea of building a small reference lamp
to share among ourselves. I'm sure many readers of the List will immediately
recognize the pitfalls in that kind of approach *but*, regardless of the
objections, personally, that would NOT keep me from participating in the
project, since this is an idea keep coming back to every now and then, and
every time one commercial radiometrically-calibrated lamp standard come up
for sale on eBay, such as the one here :
http://gamma-sci.com/products/rs10b.html
Problem is, as you know, this lamp assembly is so expensive, no amateur
color enthusiasts could ever justify its cost of acquisition, especially for
the mere purpose of comparing various instruments response -- unless one has
deep pockets... As you would guess correctly, some List readers would even
argue, rightfully so, perhaps, that monitor's spectra are not remotely
comparable to the shape of this lamp spectra, and any effort to try to build
correction matrix factors, based on the response from the instrument to the
lamp, would be in vain since, they will argue, that this approach would
induce measurement errors, even if the effort actually affords us the means
of usefully starting to make inter-instrument agreement comparisons.
Minolta's statement with regards to the impossibility of every comparing
across various instrument's geometry and light sources is the sad truth, to
my knowledge. But this should not be holding us from launching into a lamp
project ;-)
/ Roger
> -----Original Message-----
> From: argyllcms-bounce@xxxxxxxxxxxxx [mailto:argyllcms-
> bounce@xxxxxxxxxxxxx] On Behalf Of Juergen Lilien
> Sent: 2 octobre 2010 11:01
> To: argyllcms@xxxxxxxxxxxxx
> Subject: [argyllcms] Poor Man's Reference Light Source (was: ColorMunki
> measurement drift)
>
> Hello!
>
> Roger Breton wrote:
>
> > The lamps these instruments are calibrated against are either PTB,
> > NIST or NRC traceable, within their respective uncertainty budgets,
> > which usually translate into fractions of delta Es.
>
> This reminds me of an idea I had some days ago...
>
> Wouldn't it be very handy to have a small very stable light source for
> reference purpose, that could easily (at low cost) be shipped between
> interested ArgyllCMS users?
>
> This could be measured with the best (most accurate) instrument available
in
> the user base, to have a reference point. Maybe the results could even be
> used with the new correction matrices feature?
>
> My first thought is, that this should be based on a high CRI white LED
with a
> very stable energy source (regulated/temperature compensated, lithium
> battery based), all packed in a durable box.
>
>
> I've read lately an interesting text on the inter-instrument agreement by
> KonicaMinolta: http://goo.gl/kgrr The conclusion "...it is not (or only
within a
> specific tolerance) possible to compare absolute measuring results of
> different instrument types!" is once more disillusioning.
>
> So what do you all think, is it worthwhile to follow up on the "Poor Man's
> Reference Light Source" idea?
>
>
> Regards, Juergen
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