Hi, I'm taking the freedom to forward the response to lcms mailing list. Forgive me if any inconvenience, but I think this could be of interest to other users too.
>ISSUE: >---------- > I create 2 profile for my monitor using Adode Gamma > software. Both the profile are created in exactly similar > method, except that is chose different "Color Temperature" > for each of them. Now i use LittleCMS to convert a RGB value > to another RGB valued using the profiles a "Source" and > "Destination" profiles, and using Absolute colorimetric as the > indent.. i.e i am just trying to scale the image from one Color > Temperature to another. > If i give same R, G, B values (i.e a grayscale image) the output > is an R, G, B values which now are not same (neither close by). >So in this case an image which is a Grayscale will become a Colored >image. > > Ex: 255 , 255, 255 as input will give me 255, 252,189 as output. > Is this correct ?? > > If i used any other intent, the output is similar to the input. > > I have observed this in ICM also. Welcome to the wonderful world of color! ;-) This is not a bug, nor a problem. Is the correct behavior. I will try to do a quick explanation by an example. For this experiment you would need two monitors, which you should be able to set hardware white point (temperature). Place both monitors side by side. Set first to D50 (5000K), and second to D93 (9300K). Do it adjusting monitor controls. NOT by using any software. Then, using your favorite paint program, draw a white rectangle with value (255, 255, 255) on both screens. Take a look. The D93 monitor will show the white patch as "bluish" whilst the D50 will be quite yellow. This effect is not noticeable unless you place both monitors together. It happens that eyes got used to monitor and somehow "discounts" these blue/yellow cast. This is know as "chromatic adaptation", and is a important part of human vision. So, if you were using a color management system, you could transform this white to look same in both monitors, no matter which hardware white point they are using. And certainly a CMM can do that, this is the goal of absolute colorimetric intent. So, in the D50 monitor, the CMM would add some blue to compensate the yellow, and in the D93 monitor some yellow to compensate the blue. In the other hand, most times you don't need this "match to screen" feature. Your eyes are used to the hardware white point, and want gray to be neutral with respect to monitor. This is how works rest of intents: perceptual, relative colorimetric and saturation. Absolute colorimetric is rarely used, only to do match to screen or proofing. Hope this helps, Marti Maria The little cms project http://www.littlecms.com [EMAIL PROTECTED] ------------------------------------------------------- The SF.Net email is sponsored by EclipseCon 2004 Premiere Conference on Open Tools Development and Integration See the breadth of Eclipse activity. February 3-5 in Anaheim, CA. http://www.eclipsecon.org/osdn _______________________________________________ Lcms-user mailing list [EMAIL PROTECTED] https://lists.sourceforge.net/lists/listinfo/lcms-user
