Hi Bob and Andy and others
I have been lurking all week re this subject, and find the discussion
interesting and valuable. Bob seems to have a valid point re the ISO
'PrintOpen' produced profiles in the 'extreme' blues on the edge of the
Adobe RGB gamut.
But as most people are going to use the readily available CMYK profiles from
Adobe and Fogra, I thought that as I had a little time today I would look at
their 'performance' on a range of RGB images.
I looked at 5 images, measuring their conversion from RGB to the 3 CMYK
profiles in this thread.
I looked at:
Average Delta e 76
Max Delta e 76
% pixels in Gamut, allowing 3 Delta e as a tolerance
The measurements use the Alwan ColorPursuit colour management workflow tool,
and are for the Relative Colormetic intent.
The Perceptual intent give slightly better figures, (but the CMYK profiles
give the same relative performance,) but the colour appearance was not as
good.
Image 1
A very saturated modern art piece, shot on a Phase One camera back, Adobe
RGB. Some of 'Bobs blues'.
ISO coated /Europe ISO coated FORGA27 /Euroscale Coated v2
Average De 7.7 11.3 11.8
Max De 40.6 55.3 65.8
%Pixels in
Gamut 39% 37% 36%
Image 2
A food shot from a Fuji S2 in s-RGB
ISO coated /Europe ISO coated FORGA27/ Euroscale Coated v2
Average De 2.1 2.7 2.9
Max De 19.6 29.0 27.0
%Pixels in
Gamut 81% 79% 80%
Image 3
A landscape shot with a large deep blue sky, scanned on a Nikon scanner into
Apple RGB.
ISO coated /Europe ISO coated FORGA27 / Euroscale Coated v2
Average De 14.0 15.9 15.9
Max De 23.0 25.9 35.1
%Pixels in
Gamut 5% 5% 4%
Image 4
Gold oriental statue, with a pastel background from a Leaf DCB, in Adobe RGB
ISO coated/ Europe ISO coated FORGA27/ Euroscale Coated v2
Average De 4.5 6.0 5.9
Max De 23.0 31.2 29.7
%Pixels in
Gamut 67% 66% 66%
Image 5
A technical image in Lab with very saturated reds and 'Bob's blues'
ISO coated/ Europe ISO coated FORGA27/ Euroscale Coated v2
Average De 11.2 13.0 12.4
Max De 72.7 81.0 80.0
%Pixels in
Gamut 41% 39% 39%
So it would seem that the ISO coated profile is, on this small sample,
technically the most accurate of the 3 CMYK profiles. It would be
interesting to compare Bobs ProfileMaker FOGRA 27 profiles to the above?
The above findings were reflected in the appearance of the images, the ISO
coated profile seemed the best visual match to the RGB images compared.
No time to do more!
Regards
Paul Sherfield
The Missing Horse Consultancy Ltd
Telephone: 01442 871752
Mobile: 07899 906385
http://www.missinghorsecons.co.uk
Apple Solutions Expert-Print & Publishing
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