[argyllcms] Re: The k and y option with a eye-one pro and dispcal

Lars Tore Gustavsen wrote:
> I'm a little confused about the -k parameter versus the -y parameter
> used with an eye-one pro and dispcal. I think I understand what the k
> option do, I'm not so sure about the -y with a spectrometer.
> If I create a cal file with no option like "dispcal -m -v normal", I
> end up with this line in the cal file for my LCD display.
> BLACK_POINT_CORRECTION "1.000000"

The option -y selects the desired operating mode for the instrument (LCD
or CRT) and also affects the default value for -k (in case you don't
specify -k). If you do specify -k as well, you can override the default
established by -y.

> If I specify -yl on th command line I end up with
> BLACK_POINT_CORRECTION "0.000000"
>
> In the documentation I read about the -k option "Normally dispcal will
> attempt to make all colors down the neutral axis (R=G=B) have the same
> hue as the chosen white point."  This means 1, I guess. But then there
> is sentence about 1 for CRT displays and 0 for LCD display, as default
> values.  So this means this is the default behavior, only if I use
> the -y option?

Yes, that's the default, if you don't explicitly specify -k.

> I mean there is no way for dispcal to understand by
> it's own if I use a lcd or crt monotor, and if that not specified it
> use default "1"?
>
> Will  the command  "dispcal -m -yl monitor" and  "dispcal -m -k0
> monitor" give the same result? I can see in both cases I end up with
> BLACK_POINT_CORRECTION "0.000000". I just wonder if there are other
> "black magic" involved when I use the -y option.

This is not only an issue of the BP handling. Colorimeters use for
instance a different color correction matrix for CRT and LCD displays to
account for the different spectra. And CRT displays require
synchronization of the instrument with the vertical refresh rate, while
LCDs don't (for instruments, which support such a synchronization).

Regards,
Gerhard


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