[argyllcms] Re: Argyll 1.1.0 RC2 luminance readings high by ~4-6% with Eye-One Pro

  • From: Alexander <adfirestone@xxxxxxxxx>
  • To: argyllcms <argyllcms@xxxxxxxxxxxxx>
  • Date: Sun, 20 Dec 2009 19:26:40 -0800

> Hmm. I checked using my Rev D., and got a discrepancy of about 1%
> at a luminance level of about 42 cd/m^2, which (last time I looked
> into this) seemed close enough, given that I wasn't sure that the
> reference (my display) was more stable than that. Looking at it again
> however, I have found that this discrepancy is explained by a bug
> in my driver - I've accidentally swapped the high and low gain
> linearity factors :-( :-( :-(
> Fixing this up and testing again over an average of 5
> readings of white with both drivers gives an error of 0.05%,
> an improvement of 20! For my Rev A instrument the agreement
> between the two drivers has a discrepancy of 0.02%.
> So it will be interesting to see if your error goes away
> with this fix.
> [I note though that there is a 12% discrepancy between
>  the absolute values of the Rev A and Rev D instruments I have
>  access to - absolute calibration is notoriously difficult.]
I also have a Rev.D Eye-One Pro (UV-Cut if that makes any difference).

When do you expect a new build (RC3?) will be posted with this fix in it?
How close are you getting to the release of 1.1.0 final?

>  Since the values read jump around slightly on my CRT, especially for
>> dark readings (probably because of the Eye-One Pro which I've heard is
>> weak at low luminance),
> The combination of a CRT display and the i1pro is not as refined as some
> of the dedicated colorimeter such as the DTP92 or DTP94 which have
> hardware synchronization to the CRT refresh period. All you can
> do with the i1pro is to use a long enough integration time to make
> the refresh influence small. A longer integration time also improves
> low light accuracy. A more interesting option might be
> to have a mode for dispcal and dispread to use the i1pro adaptive
> reading mode rather than a fixed integration time. This should
> result in longer integration times for darker values.
> Graeme Gill.
Is there a setting for integration time in Argyll?
If you create a test build with that adaptive reading mode enabled, feel
free to email it to me an I'll test it out.

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