From 22f703cab05b7cd368f4de9e03991b7664dc5022 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?J=C3=B6rg=20Frings-F=C3=BCrst?= Date: Mon, 1 Sep 2014 13:56:46 +0200 Subject: Initial import of argyll version 1.5.1-8 --- doc/CrushedDisplyBlacks.html | 85 ++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 85 insertions(+) create mode 100644 doc/CrushedDisplyBlacks.html (limited to 'doc/CrushedDisplyBlacks.html') diff --git a/doc/CrushedDisplyBlacks.html b/doc/CrushedDisplyBlacks.html new file mode 100644 index 0000000..3038384 --- /dev/null +++ b/doc/CrushedDisplyBlacks.html @@ -0,0 +1,85 @@ + + + + Crushed Display Blacks + + + + +

Crushed +Display Blacks
+

+Often people create a display profile, and then notice that when they +try and display some images using the profile, that the darkest blacks +in the image all get crushed into the black of the display. Why does +this happen ?
+
+There are many reasons this may happen, but here is a common one:
+
+The image has blacks that are darker than the black of the display, and +the color management intent being used clips out of gamut colors. So +all the blacks that are darker than the display black get mapped to the +display black. To avoid this, some sort of Gamut Mapping that maps that black +of the source image to the black of the display, while preserving the +distinction between all the rest of the colors needs to be used.
+
+Some popular synthetic colorspaces have a perfect (and unrealistic) +zero black, for instance sRGB +and AdobeRGB. Real world +display profiles have non-zero blacks, so transforming between these +two using a colorimetric intent will clip the blacks, and loose the +shadow details.
+
+

What performs gamut mapping ?

+Typically there are only two mechanisms available to perform gamut +mapping. The main one is a pre-cooked (static) gamut mapping built into +cLUT type ICC profiles. The second is an on-the-fly (dynamic) gamut +mapping performed by the CMM (Color Management Module). A limited form +of the latter is Adobe BPC (Black point compensation), which is also +available sometimes with applications or systems that use lcms. (Little +cms).
+
+

How do I fix it ?

+There are two ways of avoiding the black crush. One is to turn on BPC +if it is available in the system you are using. Sometimes it may only +be available for certain intents.
+
+The second way of fixing it is to create your display profile with +appropriate gamut mapping, and make sure that it gets used.
+
+Shaper/Matrix type ICC profiles do not support gamut mapping, since +there is only one transformation in them and it does not have the +necessary flexibility to incorporate gamut mapping. Shaper/Matrix +profiles are always colorimetric intent. So it is necessary to create a +cLUT based Display profile if gamut mapping is to be incorporated into +the profile. (Note that not all systems accept cLUT based Display +profiles). Creating cLUT profiles that incorporate appropriate gamut +mapping depends on the profile creation tools, and not all tools give +adequate control over gamut mapping to reliably fix this problem.
+
+

OK, so how do I fix it using +Argyll ?

+You can usually fix this problem using Argyll by simply creating a cLUT +based profile (the default), and telling colprof what the source +colorspace is going to be.
+
+i.e. say your source images are in sRGB space, then:
+
+    colprof -v -S sRGB.icm -D "My +Display" MyDisplayProfile +
+
+[It's usually safer to use the sRGB profile provided by Argyll than use +an sRGB profile of unknown origin. Find it in the ref directory.]
+
+This will create 3 separate B2A cLUT tables, one for colorimetric +intent, one for Perceptual intent, and one for Saturation intent. Both +Perceptual and Saturation tables will have appropriate gamut mapping +for a source colorspace of sRGB. So it is just a matter of making sure +that either Perceptual or Saturation intent is used when making use of +the display profile.
+
+ + -- cgit v1.2.3