[argyllcms] Re: Perceptual intent in Display profiles?

  • From: Roger <graxx@xxxxxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Mon, 23 Nov 2009 19:29:41 -0500


Color management in general and monitor calibration in particular is very
frustrating. When you think you have all issues covered, new ones creep in,

In reading your post, I thought your wishes might be better served by using
a true wide gamut monitor, like an HP LP2475w (700$ cdn) or something
similar. That way, you get exactly what you expect, no fuss with perceptual
mapping, the pixel you see is the pixel you expect to see. Not clipped. 

Personally, since I don't have a wide gamut display (what's my excuse?), I
stick to sRGB. When I shoot pictures with my poor Nikon D100 and only want
JPEGs, I chose sRGB in the camera. Otherwise, when I shoot RAW and want to
retain a little more control over the faith of color, I render to sRGB. That
way, I am never disappointed. But I confess my work does not involve
shooting extremely saturated colors. So sRGB is plenty for me.

Wide gamut LCDs are coming down in prices every day.

Best / Roger

> -----Message d'origine-----
> De : argyllcms-bounce@xxxxxxxxxxxxx [mailto:argyllcms-
> bounce@xxxxxxxxxxxxx] De la part de Michel Joly de Lotbinière
> Envoyé : 23 novembre 2009 02:07
> À : argyllcms@xxxxxxxxxxxxx
> Objet : [argyllcms] Re: Perceptual intent in Display profiles?
> Graeme, Roger,
> Thanks for the advice and hints. Sorry for the delay in replying, I
> really appreciate the response.
> My earlier mistake was to even bother with the smaller targets and
> medium quality option in the various programs. The medium quality
> matrix/shaper profiles were just not very good, so I switched to LUT,
> but with too small a target chart. This wasn't a good basis for
> comparisons. The improved grayscale linearity, absence of
> colour-casts, and separation in shadows/hightlights of these larger
> ArgyllCMS lut profiles is really good now in colour managed
> applications.
> Yesterday I went through another calibration/profiling exercise and
> used dispcalGUI (and Argyll 1.0.4 )to calibrate to the sRGB curve and
> profile the LCD panel using the 512 patch "large" chart provided with
> dispcalGUI, and finally specifying a plain LUT profile, another using
> gamut-mapping options, with the sRGB profile included in the Argyll
> 1.1 RC1 archive as the source space (most of the photos I look are
> already in the sRGB space), and finally with AdobeRGB as the gamut
> source space: so colprof -S whatever.icc -cmt -dmt were the options
> used.
> My simple idea was that a real perceptual conversion from working
> space to monitor space would be an advantage in editing pictures,
> since distinct colours outside the LCD gamut would be mapped
> perceptually to distinct in-gamut LCD colors as far as possible,
> instead of simply all mapped to the nearest colourimetric in-gamut
> colour, thus losing gradations.
> Using these various monitor profiles with a photo that had some pretty
> intense out-of-sRGB-gamut colours, I've realized the whole idea is not
> adapted to editing tasks: in effect, the gamut mapping means a visual
> desaturation of the intense colours to show their gradations in the
> working space data--the dull appearance of the AdobeRGB-->monitor
> gamut mapping is really an artifact of the over-all dynamic range
> compression that Graeme mentioned. The sRGB-->monitor profile had less
> of an effect, but then what's the point? So this perceptual mapping in
> a monitor profile is not very useful for accurate editing of what the
> photos actually contain.
> It's probably better to deal with any visible issues of out-of-gamut
> colours in the conventional way, adjusting their luminosity &
> saturation to suit the destination (using proofing, etc.).
> Anyway, the upshot of all the weekend pixel-peeping and reading about
> colour management is that is that I understand a little more of what's
> going on, know what to expect--cf. Roger's remarks, and I'm going to
> keep things simple from now on!
> Thanks.
> 2009/11/19 Roger <graxx@xxxxxxxxxxxx>:
> > Michel,
> >
> > Je pense que tu attends trop du profil, une fois la calibration
> appliquée,
> > dans les ombres. Considères ton choix de gamma et le gamma "natif" de
> > l'écran. Considère aussi que, pour obtenir le noir que tu demandes,
> il est
> > possible que la calibration doive assombrir les ombres au-delà de ce
> que tu
> > crois acceptable. Peut-être qu'en réalité ton écran montre trop de
> > différentiation dans les ombres alors qu'il n'y en a pas vraiment.
> >
> > Bitte excuse my french / Roger
> >
> >
> >

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