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

  • From: Rishi Sanyal <rishi.j.sanyal@xxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Mon, 20 Jun 2011 14:18:57 -0700

"But then those correction curves would only be strictly valid for a
given pair of measurement device and display. "

Exactly. Which is why I think they worked better in the days of CRTs
with less variability between phosphors. These CRTs also typically had
a sRGB-like response.

More channels would make a colorimeter more robust, yes. More channels
would essentially allow for more 'sampling' across the spectrum,
possibly reducing the inaccuracies introduced by narrower primaries &
unmatched filters.

-Rishi

On Mon, Jun 20, 2011 at 2:15 PM, Knut Inge <knutinh@xxxxxxxxx> wrote:
> "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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