[argyllcms] Re: Perceptual intent in Display profiles?
- From: Roger <graxx@xxxxxxxxxxxx>
- To: argyllcms@xxxxxxxxxxxxx
- Date: Mon, 23 Nov 2009 19:29:41 -0500
Michel,
Color management in general and monitor calibration in particular is very
frustrating. When you think you have all issues covered, new ones creep in,
invariably.
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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