Total Area Coverage for Uncoated Papers

[dwanehollands]

Hi All,

Just wondering what TAC (TIL) people are using for uncoated (bond) papers for CMYK production. I created a quick 'photoshop iCC" using 260%, Heavy GCR and 28% gain.

The results were ok-ish. Lighter than using a 320% of course! But not too light or washed out. But I think my GCR must be too high, since blues/purples were dominated a lot by black and prevented as good a match.

Any tips or tricks?

 

[Damo77]

Hi Dwayne,

Well, you're asking about the length of a piece of string, in a way. But I would say you could go to 290-300.

What did you use to base your profile on? 28% gain seems very specific, for example.

And yes, your dark colours will get very muddy with heavy GCR - I like to keep it low if possible.

 

[dwanehollands]

Hey Damo77,

Thanks for your response. Ok, thanks for the tips about low GCR. I used SWOP uncoated ink set for building the profile.

 

[meddington]

You might also try building a profile from an uncoated characterization data...your own of Fogra29 for example, and use a software a bit more competent than photoshops antiquated engine. This, a TAC of 260-300, and a watching your black on press might help.and of course, perhaps fingerprinting uncoated on press toward say G7...

 

[Alois Senefelder]

Ucoated Paper Specs

Ucoated Paper Specs

Hi Dwane, Why are you using SWOP (Specifications for Web Offset Publications) profile ???? you are Sheetfed Printers ??? if so use "Sheetfed Specs !!! Try using
GRACol Guidelines for Uncoated Paper.
Line screen 100/110 TAC 240-260% PaperDB - 0.17 SIDs K1.25 C 1.00 M 1.12 Y 0.95
Total Dot Gain% K28 C 26 M 26 Y 24 Print Contrast K 20 C 17 M 16 Y 17

OR Google ---- Bundesverband Druck for the European Print Specs instead of American !


Regards,

Alois

 

[Lukas Engqvist]

300% ink on uncoated??? How long drying times are you anticipating. To high total ink the press will need to compensate by cutting density. Better lower percentage and higher density for more vibrant colours. This is a real weakness in "standard" or default prfiles supplied with software IMO.
240-260% is normal. I do not trust Photoshop as a good ICC making program, there are better. I would say at these lower ink limits mean you want to be able to distinguish differences in dark colours and that would mean using UCA instrad of GCR (some reasearch actually defined UCA as a special case of GCR so I do admit to proposing a paradox).

Now there is one thing more that speaks for UCA. Remember inks are a fairly low %-age pigment. Printing black first preps the paper so that the other pigments are not so quickly drawn into the paper fibres letting the pigment be more superficial and thus giving brighter colour with less risk of drying too quick (forget the technical term for the dusting of colours)

The FOGRA 29 is an ok profile provided you print on a paper as yellow as ISO standard, which is not what our customers order. The papers we use are much bluer than the ISO standard and so we must have our own profile.
Looking at the gamut in 3D you should not be surprised that you loose dark saturated colour, but that has to do with lighht being dispersed differenty on an uncoated paper.
Note that in digital printing it is possible to have higher ink coverage and brighter colours, this because the ink is above the paper.

 

[meddington]

A Tac of 300% for uncoated might indeed be optimistic, but it could depend on the porosity of the specific paper and the printing process. One could always run a TAC target (Images) to determine the ideal for the specific paper.

Of course one of the caveats for heavy GCR is that running higher black density, for text for example, can "muddy up" the images. If you have the luxury of running a test form to optmize the density and tonality, as well as determine the ideal TAC for separations, that would be your best bet.

 

[Alois Senefelder]

Wisdom !!

Wisdom !!

Hi Dwane, A word to the wise ! ---- are you trying to print a " Commercial Acceptable Job" -- or trying to print for other printers "Bombarding" you with "TAC" "GCR" "TVI"
and all the other print Spec.????????? etc etc


Regards,

Alois

 

[Mike Strickler]

Uncoated, TAC, and GCR

Uncoated, TAC, and GCR

Hi Dwayne,

I agree with Mike: stick with a TAC of 260 or below for uncoated. I also endorse the idea of going with a well-tested data set such as Fogra29, if you are making your own profile, which should be done in a bonafide profiling program rather than in Photoshop. Be prepared to edit the white point to match your actual substrate.

As for GCR "muddying" your dark colors, this is a common complaint but is based on some misunderstandings. First, GCR doesn't remove "color," as some believe, but replaces CMY gray with K-only gray, even in relatively satuarted colors. The idea is to maintain the SAME color but do so with less CMY (which increases gray balance stability) and of course less ink overall. But because black becomes a major player it must be controlled carefully, treated like any other color. Pressmen used to UCR or a "skeleton" black may be tempted to crank up the black, treat it rather loosely--and get away with it. This will cause trouble with GCR, which is not to say that GCR shouldn't be used--it should. But once the correct black density is established it must be adhered to, not used as a point of departure for further "creative" adjustments. If the black is kept under tight rein, you may also be able to start it a bit earlier, bringing some of the GCR benefit into lighter colors where in fact it's even more important. But you'll need some buy-in and cooperation from the pressroom.

 

[Louis Dery]

Hi Dwayne,

I agree with Mike: stick with a TAC of 260 or below for uncoated. I also endorse the idea of going with a well-tested data set such as Fogra29, if you are making your own profile, which should be done in a bonafide profiling program rather than in Photoshop. Be prepared to edit the white point to match your actual substrate.

As for GCR "muddying" your dark colors, this is a common complaint but is based on some misunderstandings. First, GCR doesn't remove "color," as some believe, but replaces CMY gray with K-only gray, even in relatively satuarted colors. The idea is to maintain the SAME color but do so with less CMY (which increases gray balance stability) and of course less ink overall. But because black becomes a major player it must be controlled carefully, treated like any other color. Pressmen used to UCR or a "skeleton" black may be tempted to crank up the black, treat it rather loosely--and get away with it. This will cause trouble with GCR, which is not to say that GCR shouldn't be used--it should. But once the correct black density is established it must be adhered to, not used as a point of departure for further "creative" adjustments. If the black is kept under tight rein, you may also be able to start it a bit earlier, bringing some of the GCR benefit into lighter colors where in fact it's even more important. But you'll need some buy-in and cooperation from the pressroom.

Hi Mike,
I agree with your description of GCR usage.
I only want to say that all GCR (from different profiling or other applications) are not "equal" or the same. Each vendor develop its own GCR calculation algogithm and not allways render color at its best. That is why many report that GCR is destructive or creates muddy dark saturated colors.
Before thinking to use strong GCR, user should compare different solutions in order to get the best color reproduction they want to achieve. I know some well known profiling tools which have a very bad GCR algorithm, specially bellow 240 TAC.

Be carefull!

Louis Dery
TGLC inc.
TGLC Solutions de Gestion de Couleur et Contr�le Couleur: Logiciels PerfX, Formation, Int�gration, Certification

 

[Alois Senefelder]

re TAC

re TAC

Hi Dwane, Speaking from the Pressroom Perspective, I agree with the last two input comments - - just use the already well tried "Specs" from Fogra, Gracol or BVMD.org.
and use your time in a more productive overview of "Pressroom Operations"

Regards, Alois

 

[Lukas Engqvist]

Alois,
we are not dissagreeing, merely pointing out that though the Datasets of say FOGRA is well tried the readily available "standard profile" ISOuncoated has an ink limit of 320%.
It is a productive use of time to set up a system that does ensure less problems in production and post production. Yes it does take time, and knowledge, but the payoffs are longterm improvements in production flow.

It must be allowed to discuss and if necessary point out limitations of and/or question even well tried standards. It was in taking a different route than the well tried that America was discovered

Would you please expand on "Pressroom Operations" that would render this discussion unnecessary.