Re: Fogra 51 and 52
Re: Fogra 51 and 52
- Subject: Re: Fogra 51 and 52
- From: Refik Telhan via colorsync-users <email@hidden>
- Date: Thu, 13 Jun 2019 14:42:49 +0300
- Thread-topic: Fogra 51 and 52
Hi Graeme,
The neutrals have always been neutral in relation to the paper, be it M0 or M1.
It totally depends on the way we are doing the color conversion, which is
typically relative colorimetric with black point compensation (on perceptual).
The "coldness" I am referring to is the coldness of the FOGRA51/52 separations
in comparison to ones made by FOGRA39/47. When we do the color conversion to
both colorspaces in Photoshop in RelCol+BPC mode, we end up with two distinct
CMYK structures. Both are paper relative. What we are seeing in Photoshop (with
Proof View OFF) is the color of the ink-film made by the CMYK layers.
Just prepare as a set of RGB images that also contains CIELAB-neutral black and
white photography. Send these images two different printers. Printer A is still
on the FOGRA39 track and Printer B has made the switch to FOGRA51. Tell them to
use the same inks and the same paper type, say Sappi Magno Satin or Lecta
Condat Matt Perigord (both are very close to what FOGRA51 has picked as
reference).
We are assuming that both printers are able to hit the targets of their
respective printing conditions. In the end, you will see that the prints made
by Printer A are "visually" more neutral then what Printer B did. This is the
problem plaguing the industry since the very first day FOGRA51/52-based
profiles have been released. And this is why these profiles have faced lukewarm
acceptance.
While the proof-to-print match has immensely improved with the switch to M1
measurement mode in FOGRA51, the neutrality of the ink-film is broken. Using
the same inks and the same papers that we have been using for the last 10-12
years, we are now having colder (yellow-deficient) separation/prints.
The situation is catastrophic along the FOGRA47-FOGRA52 line. I typically
generate higher GCR versions of datasets to use in situations where gray
balance is critical. Long years ago, I have generated many variants of FOGRA39
and FOGRA47 using a quite old version of PrintOpen (v4.0.5.2). These are still
being used in daily production.
I have tried to the same with both FOGRA51 and FOGRA52 using i1Profiler v1.8.2
starting from the built-in .mxf files. Below is the list of CMYK values for a
neutral gray step wedge.
L* C M Y K
(a*=b*=0)
95 4 3 3 0
90 7 5 5 1
85 10 7 7 2
80 13 9 9 3
75 16 11 10 4
70 19 13 12 7
65 23 16 15 10
60 26 19 17 13
55 30 22 19 16
50 34 26 22 21
45 37 26 22 21
40 41 32 25 36
35 44 35 25 44
30 48 37 25 53
25 52 39 25 60
20 56 42 24 67
15 62 44 22 67
10 70 48 19 79
05 80 51 15 84
00 99 56 9 90
The loss of yellow is also evident in the FOGRA51-based
"PSOuncoated_v3_FOGRA52.icc". Just view the neutral rendering curves of
"PSOuncoated_v3_FOGRA52.icc" and the FOGRA-47
based"PSO_Uncoated_ISO12647_eci.icc" profiles next to each other.
i1Profiler 'freely' replaces yellow with black (in the dark end of the tonal
range) and represents the worst case. Other profiling packages are more
"merciful" against yellow, but they all reduce it is to some extent when they
are using the FOGRA52 dataset.
While the yellow ink is not to most significant ink in terms of building the L*
value of the rich black, it is very important in creating other physical
properties of the printed image. It carries the waxes that provide
rub-resistance and the varnishes that provide gloss. And this gloss adds to the
visual depth of the rich black. Yellow ink also "masks" the pinkish reflection
made by the solid magenta ink.
As the black ink itself is a very strong neutralizing agent for the rich black,
you may "colorimetrically" think of reducing yellow down to the edge of
extinction, which i1Profiler does, but both visually and physically the printed
image starts suffering.
In short, FOGRA39/47 dataset based profiles create "neutral ink-films" that
work on "all" papers, with or without OBA. Their printed image is always
neutral relative to paper and is visually acceptable. But FOGRA51/52-based
profiles are not producing neutral ink-films. High OBA, M1 measurement mode,
choice of profiling package, lower TAC (in the case of FOGRA51) are all
contributing factors to some degree.
As a new revision of ISO 12747-2 is approaching, this issue needs to be
discussed openly and extensively.
Best regards,
--------------------------------------------------------
Refik Telhan, EE B.Sc.
Light and Color Management Consultancy
Aydogdu Sokak 12A, Tarabya Mahallesi
Sariyer, 34457, Istanbul, Turkey
Mobile: + (90) (532) 426 21 87
--------------------------------------------------------
On 13.06.2019 07:22, "colorsync-users on behalf of Graeme Gill via
colorsync-users" <colorsync-users-bounces+rtelhan=email@hidden on
behalf of email@hidden> wrote:
Refik Telhan via colorsync-users wrote:
Hi,
> The problem actually appears in the color conversion phase. Given that
you use a
proofing substrate that matches the print substrate in terms of color and
OBA class, the
proof and the print matches. But rich blacks are coldish/bluish/purplish by
seperation.
And the loss of yellow is not limited to the gray axis, all colors that
should contain
high amounts of yellow lose some of it.
All this is correct as far as the measurements are concerned. The paper has
FWA/OBE,
so has a blue leaning white point under M1. Neutrals composed of CMY tend to
have a similar white. Neutrals composed of K tend to be warmer (perhaps
because
the K blocks the UV more effectively). So neutrals composed of CMYK tend
to have little or no Y because the K is making them warm enough.
> In short, the separation itself is now colder than
what it used to be under FOGRA39/47.
The neutrals are neutral in relation to the white of the paper under M1.
Whether they appear neutral depends on how well your viewing environment
matches the measurement conditions assumptions. A standard viewing booth
with M1
illumination does not match the measurement assumptions, because the
neutral paint it uses does not have FWA/OBE to match the paper, and
so appears warm by comparison, throwing off the observers white point
adaptation state, making the print appear cool.
Cheers,
Graeme Gill.
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