[argyllcms] Re: Perceptual intent in Display profiles?

  • From: Michel Joly de Lotbinière <michel@xxxxxxxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Tue, 24 Nov 2009 01:35:40 -0500

Well, just like you, sRGB really covers practically all of what I
need, but I get a little carried away by all the possibilities in the
argyllCMS tools.

And to Gerhard: I'll have to look into those options, I missed them.

On Mon, Nov 23, 2009 at 7:29 PM, Roger <graxx@xxxxxxxxxxxx> wrote:
> 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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