By suggesting that clients use sRGB as their working space, they are insuring that what they see will be what they get as much as possible." Before images are printed here they must be converted to sRGB. We suggest sRGB as the working space because that is the color space that the printers require. A larger color space, in theory, allows a greater range of colors and dynamic range to be captured and manipulated. It's a similar question to the one above about bit depth. Consequently, working in a larger color space does not offer any advantage from a printing standpoint. " Why sRGB? sRGB is the working space for all our photographic printers. If it's a Lab like Mpix or White House Custom Color, find out which one they prefer.įor Mpix, they suggest sRGB. Use the color space that is specified by the print lab. The question is how are you going to display your photos?
Pro Photo RGB is the largest with the widest Gamut of color They are Pro Photo RGB, Adobe RGB (1998) and sRGB. I'm not sure if this is exclusive to libraw or if this was also present in the original dcraw since I don't have the original dcraw currently.We've talked about three different color spaces created by mixing Red, Green and Blue (RGB). Looks like it's almost the correct set of values, but somewhere along the way there was probably a typo. In any case, the sums of the XYZ values found in the ACES profile I extracted are 0.97056 1.00145 0.76492 respectively. This is because these values take it from the connection space, which is CIE D50 2 degree observer XYZ space, to RGB, and chromatic adaptation to the media white point is done from there. The XYZ values in the ICC profile which form the RGB to XYZ matrix ('forward matrix') though should sum to the connection space illuminant however, which is D50 regardless of the media white point. There's no issue with that, I'm aware of that aspect of Coffin's color profiles and they have correct values in the MediaWhitePoint tag. The D65 part comes in the MediaWhitePoint tag in the ICC profiles. The ACES one was the only one that was abberant. I checked the ProPhoto and sRGB XYZ values, and when arranged in a matrix the rows sum to the expected D50 values. Or is there a reason the ACES profile has an apparently incorrect white point? Anyone have any insight on that? Forums:
Note that even if the white point is D65 or D60, the rows of the forward matrix should sum to the D50 values. though it's common to see icc profiles use the ASTM values for D50, that being xyz=0.96422,1,0.82521). I would propose changing the forward matrix for ACES toįor consistency with the ICC PCS illuminant (xyz=0.964203, 1, 0.82491). That explains why images developed with dcraw_emu's ACES profile are significantly warmer than they ought to be. The value I get is 100.05, 0.853, 5.06, which corresponds to an RGB value of 255, 254, 245 which is a pale yellow color. While it is common for the L*a*b* values for white to be slightly off due to hexadecimal arounding error, the issue here is much more serious.
When using the command xicclu -ir -pl -s255 aces.icc and entering 255 255 255, I should have L*a*b* values of 100,0,0 returned.
This is approximately a 4700K white point, which is significantly out of line with the ICC specifications.įurther inspecting the profile using argyllCMS's xicclu function revealed further issues. The rows should sum to a D50 white point. So, I extracted the ICC profile from the photo and took a look at the primaries, shown in the forward matrix below. I was comparing the output of photos developed with ACES to output with ProPhoto in a color managed photo viewer, and I noticed the colors just seemed a bit off, they looked warmer than I would expect. This is in reference to using dcraw_emu, though I imagine this could be an issue for libraw in general.