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: Sat, 15 Jun 2019 04:50:59 +0300
- Thread-topic: Fogra 51 and 52
Hi Graeme,
>> right, but the CMYK "structure" is irrelevant - it's the color that counts.
In this case CMYK "structures" are relevant. The printing conditions for
FOGRA39 and FOGRA51 are very closely related. In real life they are printed
with the same inks on the same coated papers with almost identical primaries
and very slightly different TVI curves (CMY balance is unchanged). Hence, the
kind of structural change that is taking place is causing a "visible"
yellow-deficient appearance. Shaving off a hefty amount of yellow from the rich
blacks is causing a change in the apparent color. Printers had no problem with
the CMY+K gray balance of FOGRA39. On the way to a better proof-to-print media
white match, FOGRA51 lost the internal CMY balance.
>> Evaluating it in what conditions ?
Evaluation is always done under the same ISO 3664:2009-compliant light sources.
The comparison has physically been made in the same light booth.
>> Sounds like they are being misused.
All those who tried their hands at FOGRA51 and FOGRA52 are competent printers
who know what they are doing. All have the tools to create and maintain the
relevant printing conditions. The apparent coldness of the FOGRA51 and FOFRA52
separations starts with the initial conversion, before the files reach printers.
>> As it should be from the measured color. If that doesn't look right at the
>> end of the day, then the
>> measurement conditions aren't a match for the viewing conditions. So change
>> one to match the other.
The viewing conditions supplies the reference to the whole process. If a
FOGRA51 or a FOGRA52 does not look right being compared next to a FOGRA39 or a
FOGRA47 print under this reference light, what has to be changed is the color
separation, not the viewing condition or the measurement mode.
>> Right. And as you raise black you will lose yellow, because the K only black
>> is warm when measured
>> on the FOGRA51/2 paper under M1.
It is same black ink and the same printing stock that are being used for
FOGRA39 or FOGRA51. Measuring it in M1 mode does not make black ink any more
yellow than the same black ink measured in M0 mode. Its yellowness is only
mathematical relative to the lower b* value measured in M1 mode. While what you
say can be seen as "colorimetrically" correct, this cannot be used as an excuse
to shave off yellow in the rich blacks. Yellow ink is more than a colorant; it
carries waxes and varnishes that add rub-resistance and gloss respectively.
Hence, you cannot freely replace it black on the basis of "colorimetric
correctness". This decision is up to the printer and more importantly to do
print buyer. There is one more subtle problem here. Yellow ink is "last" ink in
the print sequence. Hence, when any reduction takes place, it is distinctly
"visible". But during the buildup of the rich black in a FOGRA51-certified
proof, all the inks are finely mixed up. Hence, the proof both measures and
appears "correct" but the print definitely shows the yellow is missing in
comparison to its FOGR39 counterpart. We all know that colorimetric sameness
does not guarantee common/consistent color apperance. As much as proof of the
pudding is in the eating, proof of the printing is in the "seeing". Print
buyers only come back to you when they like what they see.
>> The amount of yellow is irrelevant - it's the measurement and appearance
>> that counts.
>> CMYK is just a way of getting to a result.
I disagrre. The amount of yellow is very relevant. Comparative work done on
more than occasion has confirmed that the new set of profiles are producing
cooler/colder ink-films, that is highly visible. And print buyers do not like
that.
>> It's not the software that's doing this, it's the data. The measurements say
>> that the CMY black is in
>> line with the paper white point, while the K only black is warm. So as you
>> increase the K, yellow has
>> to be dropped. i.e. it's all working as intended. (Although dealing with a
>> CMYK device that has different
>> CMY and K blacks can make it difficult to get smooth transitions in the
>> shadow regions.)
In fact it is a combination of both. I have recently tested three different
profiling packages with M0-M1-M2 data grabbed from G7 and TVI-calibrated prints
made on coated and uncoated papers (a total of 12 datasets and 36 profiles).
X-Rite's i1Profiler is the most aggresive in knocking down yellow in the
presence of black. ColorLogic's CoPrA4 does not go that far. But the good old
ProfileMaker 5 keeps CMY balanced even in very high GCR settings. CMY goes down
together as black increases. I will be supplying you the link of the Dropbox
folder where I have stored the results of this study. From the standpoint of a
printer, yellow ink is quite important. We should not be modifiying it on
purely colorimetric grounds.
>> Right. So if you need more yellow for reasons other than the color, then you
>> need to reduce K in your
>> separation, or switch to M0 or M2 conditions, or use a paper with less
>> FWA/OBE, or use a black ink that
>> is cooler and/or blocks less UV.
The solution is simply to use M2 measurement mode to grab data from any paper
(with or without OBA) to build the profile for color conversions. And M1 data,
that you can grab simultaneously using dual-scan mode, can be used to create
the profile that you will using for all proofing (soft and hard). With moderate
to high OBA papers becoming reference papers, the M0 mode, with its unaccounted
amount of UV, should definitely be declared obsolete.
>> But they are producing neutral ink films as confirmed by the
>> measurement/profile data. It's just not
>> the sort of separation you are used to.
>> Dealing with FWA/OBE is hard and can never be perfect, because of
>> uncontrolled levels of UV in real
>> viewing environments. That's the trade-off for switching to cheap paper. If
>> you (really meaning your
>> customer or customers customer) don't want these problems, don't use FWA/OBE
>> laden paper.
This neutrality, I would say,is only mathematical, When you transpose a FOGRA51
separation of a CIELAB-neutral RGB image to FOGRA39 by assignment, you will see
that this separation is relatively colder what the FOGRA39 does from the same
image file. The coldness of the FOGRA51/52 separations relative to the
FOGRA39/47 separations is a real issue.
Sooner or later all artificial lighting will lose the UV component. Apart from
some special full spectrum LEDs, all other white LEDs use a blue chip (at
around 430 nm) and a yellow phosphor. The very few special ones use a 405 nm
chip and R+G+B phosphors. Hence, in the absence of UV, OBAs in the papers will
soon become irrelevant. But until that day (and even after that), M2
measurement mode appears to be the safest way to get round the problem.
Proofing should be done on substrates that match the OBA levels of the print
stock. And M1 mode can be used to "verify" the proof and the print.
>> [ Sorry - I know a lot of the pain here is that an industry/structural
problem has been created. FOGRA51/52 has been thrown in as if it
was an "upgrade" from what has come before, whereas it is really
a completely new paradigm. So there is dislocation. ]
I am just trying to figure out a simply solution that can be easily practised
by everybody. Let us not forget that these printing conditions, datasets and
profiles are also practical models for in-house custom profile making. Just use
any calibration method (G7, TVI or as-is). Grab M1-M2 data in dual-scan mode.
Use M2 for conversion profiles and M1 for proofing profiles. Use proofing
substrates with matching OBA.
Thanks and regards,
Refik
-----------------------
On 14.06.2019 02:17, "colorsync-users on behalf of Graeme Gill via
colorsync-users" <colorsync-users-bounces+rtelhan=email@hidden on
behalf of email@hidden> wrote:
Refik Telhan wrote:
Hi,
> 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.
right, but the CMYK "structure" is irrelevant - it's the color that counts.
> 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.
Evaluating it in what conditions ?
> 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.
Sounds like they are being misused.
> 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.
As it should be from the measured color. If that doesn't look right at
the end of the day, then the measurement conditions aren't a match
for the viewing conditions. So change one to match the other.
> 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.
Right. And as you raise black you will loose yellow, because the K only
black is warm when measured on the FOGRA51/2 paper under M1.
> 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.
The amount of yellow is irrelevant - it's the measurement and appearance
that counts. CMYK is just a way of getting to a result.
> 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.
It's not the software that's doing this, it's the data. The measurements say
that the CMY black is in line with the paper white point, while the K only
black is warm. So as you increase the K, yellow has to be dropped.
i.e. it's all working as intended.
(Although dealing with a CMYK device that has different CMY and K blacks
can make it difficult to get smooth transitions in the shadow regions.)
> 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.
Right. So if you need more yellow for reasons other than the color, then
you need to reduce K in your separation, or switch to M0 or M2
conditions, or use a paper with less FWA/OBE, or use a black ink
that is cooler and/or blocks less UV.
> But FOGRA51/52-based profiles are not producing
> neutral ink-films.
But they are producing neutral ink films as confirmed by the
measurement/profile
data. It's just not the sort of separation you are used to.
Dealing with FWA/OBE is hard and can never be perfect, because of
uncontrolled levels of UV in real viewing environments.
That's the trade-off for switching to cheap paper. If you
(really meaning your customer or customers customer)
don't want these problems, don't use FWA/OBE laden paper.
[ Sorry - I know a lot of the pain here is that an industry/structural
problem has been created. FOGRA51/52 has been thrown in as if it
was an "upgrade" from what has come before, whereas it is really
a completely new paradigm. So there is dislocation. ]
Cheers,
Graeme Gill.
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