On 22 Feb 2007, Matthew Robinson wrote:
I found something rather unexpected when converting a colour from sRGB to CMYK using this new ISOCoated_v2_eci.icc in Photoshop CS2.
The below conversions were all done in Photoshop CS2 using Engine=Adobe(ACE) & Black point compensation on.
R=0 G=0 B=255
converted to:-
Intent = Relative Colorimetric, ISOCoated_v2_eci.icc C=95 M=100!! Y=0 K=0
Fogra27 C=88 M=77 Y=0 K=0
The ISO version is turning the blue, purple! Where as the Fogra27 is strikingly more blue.
Hi Matthew The 27 & 39 Characterization Data Sets from which the profiles were made are rather different. 27 was made a few years ago. 39 was made from Press runs to the amended ISO 12647-2 standards last year, very carefully, and then the data was tweaked to exactly match that in the standard with regards to the primary and secondary overprints. The lab values for step 81 (C100 M100) are as follows: Fogra 27L 24.43 16.18 -47.10 Fogra 39L 24.00 22.00 -46.00
The a* value for 39L is quite a lot higher.
As Louis remarked, R0, G0, B255 is well outside of the gamut of Offset. The ECI profiles are made with Print Open software. Results are somewhat different across various vendors profiles, especially near or outside the edge of the gamut. The ECI profile seems too magenta (in blues) to you and also to me. The Perfx profile seemed a little better. Another I made appeared a little lacking in magenta. All of this was in Photoshop only, and not printed. All subjective of course, and who's to say which profile is best? You should also find that the Grey Balance is nicer from the 39 data set. Fogra's publication of the data enables the industry to create their own profiles, especially useful with regard to Black Generation and TAC. Regrads |