On Tue, 10 Jan 2006, Hal V. Engel wrote:
The way I see it, the icc profile should be all that is necessary to take the RAW data from the camera and map it into an absolute working colorspace. Keep all manipulation/quantization of the original data as close to the end as possible.It is true that the profile characterizes the color space of the image. Therefore when a linear image with a profile that correctly characterizes that images color space is opened in an app that understands ICC profiles it will correct it before it is displayed but the actual data is still linear. The same applies to when the image is printed.
A true RAW image from a camera uses a Bayer pattern (spacially distributed red, green, and blue samples) specific to the camera. RAW camera images are not usable with ICC profiles. After using some algorithm to tranform to RGB (or some other formal space like LAB), then the ICC profiles can be used as described. The actual translation from camera RAW format to RGB can not be directly controlled by a profile. The profile describes the mapping produced by the specific Bayer->RGB algorithm.
The concern I and other have is that the process of creating the image from the RAW data using a gamma of 1 will tend to block up the shadow detail. I have only done a few experiments with this but using a gamma around 2.2 did yield better shadow detail. The difference was not huge but it was clearly there.
Using a gamma of around 2.2 (or 2.6 for X'Y'Z') tends to linearize the luminance significance of each bit (particularly for dark regions) so fewer storage bits are necessary, and computational errors are reduced.
Bob ====================================== Bob Friesenhahn [EMAIL PROTECTED], http://www.simplesystems.org/users/bfriesen/ GraphicsMagick Maintainer, http://www.GraphicsMagick.org/ ------------------------------------------------------- This SF.net email is sponsored by: Splunk Inc. Do you grep through log files for problems? Stop! Download the new AJAX search engine that makes searching your log files as easy as surfing the web. DOWNLOAD SPLUNK! http://ads.osdn.com/?ad_id=7637&alloc_id=16865&op=click _______________________________________________ Lcms-user mailing list Lcms-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/lcms-user
