[argyllcms] Re: question about monitor calibration
- From: Alberto Ferrante <alberto.ferrante@xxxxxxxxxx>
- To: "argyllcms@xxxxxxxxxxxxx" <argyllcms@xxxxxxxxxxxxx>
- Date: Sat, 26 Jan 2013 12:12:31 +0100
Dear Graeme,
I apologize for the delay in replying to your post. Your reply was very
clear and useful. Still, it raises some further questions from me
(below, inline with your text) :-)
> An ambient of 11 Lux is quite dark. That's why the gamma is increased.
> The ambient light correction is based on assumptions about the
> source viewing conditions ambient light level and brightness,
> and the correction will increase gamma if the source is brighter
> than the display, and decrease the gamma for the reverse.
> The source assumptions are base on the gamma selection. A power
> curve, Lab curve or sRGB assume sRGB viewing conditions as source (250 Lux).
> Rec709 and SMPTE240M assume TV studio conditions (1000 Lux).
My understanding was that for sRGB a "dimly lit" room was assumed. I
normally use a room with a single diffused light source on my left. I
have just tried to perform a read of the ambient light (device on the
monitor with the sensor turned to face me and the white "cap" on) with
all the lights on and the curtains open and I got a read of 27.7 Lux. My
Sekonic light meter measures 4.9EV that is approximately 80Lux in the
same conditions.
I am a bit puzzled about this...
> Because profiling records the response of the calibrated device,
> then (of course!) when you link this with a source colorspace, the
> CMM strives to reproduce the source color space accurately,
> removing as much of the destination devices "personality" as
> it can, which includes any effects of calibration. So any change
> to the device calibration _should_ have no effect if color management
> is working correctly. To change the appearance of an image you need to
> alter the colorspace it is defined to be in (ie. the source profile
> that it is tagged with), or introduce a deliberate color adjustment
> in the CMM process (say, by using an abstract profile in between the
> two device profiles, or introducing viewing condition appearance adjustments).
OK, clear.
> Calibration doesn't directly affect profiles/color managed response (see
> above).
> To make viewing condition adjustments in color managed workflows
> you need to account for it in the CMM linking/gamut mapping.
> See ArgyllCMS collink -c and -d parameters:
> <http://www.argyllcms.com/doc/collink.html#c>
I will try that, but... So far the color profile without correction for
viewing condition adjustment has proved to give extremely good results.
Printing by using professional services has given consistent results
with what I see on the monitor also from the luminosity stand point.
Thanks again for your help!
Best,
Alberto
--
Home page: http://www.alari.ch/people/alberto
Photo galleries : http://albertoferrante.name
Public key: http://www.alari.ch/people/alberto/keys/yahoo.asc
Other related posts:
