Colour managing/process controlling process colour tints

[meddington]

Re: Colour managing/process controlling process colour tints

>Just to re-iterate, if you print a number underneath the printed 50% path, it should say 50 (just like in the file), but with a densitometer it would measure when printed about 64. Had the same questions myself years ago. Designers don't understand dot gain and therefore a 50 is a 50. But in reality a 50 (in file) is a 64 (approx. on press sheet).

In Paul's defence, I think he understands this perfectly well, and isn't expecting files prepped using current ISO/Gracol profiles to print linear and still look acceptable without additional adjustment at the separation stage, but merely for the purpose of outputting straight CMYK, cut back to linear at the rip for the purposes of the tint book in question. In theory/practice, one could linearize press output, create an ICC profile of these conditions and convert all incoming RGB /CMYK towards this condition to maintain an expected appearance from proof to press, but the question is, is this desired, optimal, or beneficial in anyway. As someone earlier stated, its a bit like reinventing the wheel.

 

[disbellj]

Re: Colour managing/process controlling process colour tints

Sorry about that. I thought he was talking of printing a tint book to ISO 12647-2 international standard, not a tint book of a custom linear printing condition that conforms to no standard. Also, I agree with you Michael about the lesser need these days for tint books. People should be calibrating and profiling all devices in their workflow, and the soft-proofing and hardcopy proofing should show what one will get on the printed piece.

Don

 

[Paul Sherfield]

Re: Colour managing/process controlling process colour tints

Hi Mike and Don,

and all the other who have answered the issues.

1) If we go ahead, we will produce a number on tint books reflecting the ISO printing conditions, curves and paper types.
2) There is a demand in the UK for this, from the creators. Most do not have a colour managed desktop, screen or CM enabled correctly in software at present.
3) I thought I had was to 'double label' the tint panels with the profiled % and the real printed % for each printing condition and curves.

Thanks again

Paul Sherfield

 

[disbellj]

Re: Colour managing/process controlling process colour tints

"3) I thought I had was to 'double label' the tint panels with the profiled % and the real printed % for each printing condition and curves."

This would just add confusion. Just label the tint block as it is in software (designers are the ones using it after all, and they wouldn't know what the printed number was all about, don't know what dot gain/TVI is all about, and it would therefore cause confusion for them), while you in prepress and at the printer will know the TVI.

With the new G7 method of setting up press/paper/ink combos to neutral print density curve (tone curve), although TVI is inherent, its not set-in-stone. Put another way, TVI/dot gain is a metric that can change to meet the NPDC target for each paper type, so I may run a paper using one set of TVI's for each ink, and you may run to a similar paper but to different TVI's for each ink than I do, for you to get to the target NPDC. Both may be close, but we want our color to look the same on both presses and papers, even if the TVI to get that same appearance is different on both presses. So NPDC is defined for K and CMY, and is a better target than TVI is. See www.gracol.org for free downloads of How-To, characterization data (if you're making your own profiles), and official profiles for paper types 1/2, 3, and 5. This is for the U.S. prepress and printers. If in Europe, you want to check out FOGRA.org and ECI.org.

The main problem for me (or any other prepress or printer) is getting the customer to actually use the ICC profiles you want and need them to and them not to use the default SWOP profile in Photoshop (if in the U.S.) (Note: Even if they do use SWOP, although not good enough for real accurate color matching, the images will look "natural") (Since customers aren't being taught color management and using it correctly, then I see why you want a tint book).

Don

Don

 

[Ritchie]

Re: Colour managing/process controlling process colour tints

Paul

ISO 12647-2 is the standard our pressroom are finally beginning to implement. This is something us Prepress guys have been trying to push towards for many years.

What does the ISO 12647-2 standard actually dictate, I presume measurements are taken with Spectrophotometre on specified patches including probably 50% CMY, (to calculate a CIELAB value), does the standard specify that the dot on the *plate* should be a 50% or that the dot on the *paper* should be 50% (going back to your initial question Paul).

In your experience do most printers adhering to 12647-2 run with dot gain curves or implement techniques where dot gain can be maintained to its minimum, i.e 10-14% and therefore replicating (approximately) the CMYK swatches supplied by PANTONE. Surely if we were to produce a 40% dot on plate which on press will be 50-54%, the mix of colours will not match any colour swatches approved by PANTONE.

 

[meddington]

Re: Colour managing/process controlling process colour tints

>What does the ISO 12647-2 standard actually dictate, I presume measurements are taken with Spectrophotometre on specified patches including probably 50% CMY, (to calculate a CIELAB value),

ISO 162647-2 defines CIELab for solid primary and secondary overprints (with tolerances for primaries only) and a TVI curve based on paper type. CIELab is undefined under 100%. Gracol's G7 methodology does define a neutral print density curve via CIElab values (paper dependent and based on 50C, 40MY).

> does the standard specify that the dot on the plate should be a 50% or that the dot on the paper should be 50% (going back to your initial question Paul

The ISO standard doesn't define a target dot for plates, just the paper dependent TVI curves (none of which are linear).

 

[disbellj]

Re: Colour managing/process controlling process colour tints

If you print to the international standard in the U.S., via G7 method and GRACoL2006_Coated1v2 ICC profile for proof, your colors and PANTONE's (both using the same CMYK values) will not match each other. Why? Because obviously PANTONE didn't print to the international standard?! Their solids don't match ISO 12647-2!

Don

 

[papa v2.0]

Re: Colour managing/process controlling process colour tints

for those who say

50% in file should = 50% dot on paper

Q. what size dot will there be on the plate to replicate a 50% dot on paper?