[argyllcms] Re: Dell U2711 - is it any good?

  • From: Knut Inge <knutinh@xxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Mon, 20 Jun 2011 23:15:44 +0200

"Needed" in the world of commerce can be substituted with "what are we
able to sell and make money off of". My guess is that there are a lot
of colorimeter sales to people (like me) who dont really know what to
expect, who use it one or two times then put it in a box in the attic
because that cant find a way to use it that contribute to image/video
editing/vieweing in the way that the had been hoping.

But then those correction curves would only be strictly valid for a
given pair of measurement device and display. Wide-gamut LCD displays
have narrower (?) primaries (either color filters or peaky
backlighting) to allow for more saturated colors. Introducing more
irregularity to the frequency domain would make it generally harder to
sample "color" in a XYX/perceptually meaningful way. Further, any
assumptions made in colorimeters about typical display behaviour could
be thrown off by these displays.

I thought that the (7channel?) approach of the Spyder was supposed to
make it more robust against such display variation, although the
Hansen test seems to indicate that they have got some assembly-line
control issues.

On Mon, Jun 20, 2011 at 10:36 PM, Rishi Sanyal <rishi.j.sanyal@xxxxxxxxx> wrote:
> I was under the impression that correction matrices are always needed
> for any colorimeter due to the fact that the transmission profiles of
> the filters can never accurately approximate the XYZ functions of the
> human eye-brain system. This is certainly not hard at all to believe,
> as the X, Y, Z spectra are complicated, not simple gaussian curves or
> spikes at certain wavelengths.
> Therefore a correction matrix is needed to essentially approximate the
> total signal (# of photons, e.g.) a device with an excitation profile
> of, say, X (in other words having a transmission profile that looks
> like the excitation curve for the X function) would 'see' when given a
> certain color.
> Correct me if I'm mistaken.
> -Rishi
> On Mon, Jun 20, 2011 at 1:30 PM, Alan Goldhammer
> <agoldhammer@xxxxxxxxxxx> wrote:
>> NEC do source a colorimeter from X-Rite that has been modified with a filter
>> to work on wide-gamut displays.  I've been using it with dispcal to profile
>> mine and it works fine without a correction matrix file.  I have followed
>> the Ethan Hansen evaluations with great interest but even he pointed out
>> that these corrected colorimeters do a good job for the monitors they were
>> designed for.
>> Of course if you have the appropriate instrumentation you can prepare your
>> own correction matrix using the tools that Graeme has developed.
>> Alan
>> -----Original Message-----
>> From: argyllcms-bounce@xxxxxxxxxxxxx [mailto:argyllcms-bounce@xxxxxxxxxxxxx]
>> On Behalf Of Rishi Sanyal
>> Sent: Monday, June 20, 2011 3:59 PM
>> To: argyllcms@xxxxxxxxxxxxx
>> Subject: [argyllcms] Re: Dell U2711 - is it any good?
>> The correction matrix is something they download into the firmware on
>> the colorimeter. Try:
>> http://lumita.com/site_media/work/whitepapers/files/xrite-wp-3a.pdf
>> On Mon, Jun 20, 2011 at 12:15 PM, Knut Inge <knutinh@xxxxxxxxx> wrote:
>>>> Knut, the Spyder 3 is a colorimeter, yes? As a colorimeter, it's not
>>>> going to work well on wide-gamut displays unless the correction matrix
>>>> supplied by the manufacturer is for wider-gamut displays. Even then,
>>>> there's bound to be some inaccuracy. Your best bet is to use a
>>>> spectrophotometer to either make the profile, or to at least make the
>>>> correction matrix for YOUR monitor + colorimeter combo, then use the
>>>> colorimeter with that correction matrix.

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