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jstotz
01-10-2011, 02:48 PM
I was making a color setup for an uncoated paper and had a few questions.

First I made a color setup with the GRACoL uncoated beta characterization data in a CMYK PCO. Then I made another color setup with a press as the PCO and the simulation set to the GRACoL uncoated beta color setup and linear as the curve. I made a set of linear plates and ran them on the press. While doing the press run, and using SpotOn to monitor the color, I realized that the optimal ink densities were going to produce more saturated colors and a larger gammut than the GRACoL uncoated beta data set. I finished the press run with those densities and read in a bunch of sheets. I was using an IT8 so I averaged them in Profile Maker and loaded the averaged data into CF in the measurement icon for the PCO.

CF then built a curve that would get me from the linear device response to the GRACoL uncoated beta response. I then made a set of plates with this curve and put them on press. I was hoping that even though the densities and the saturation of the solids and traps was higher that what was specified in the GRACoL uncoated beta data set, the curves would work out correctly. This appeared to be the case. I got reasonable looking press sheets, however, I needed more weight in the black midtones. So I went to the simulation adjustment and added 3% to the black at the midtones and made a new plate. This gave me some good press sheets and I have decided that this will be my uncoated standard for this press.

So now my questions.

1. I have added a KPS proofer SCO to this color setup to produce proofs that should match this press sheet. How do I tell CF what these final press sheets actually look like? In the simulation section of the PCO, CF has built a profile, but I think it was built from some combination of the GRACoL uncoated beta data set and my adjusted black curve. Since the gamut of my press sheets is different, how do I get that info into CF?

2. Since I'm effectively making my own standard, did I use the right procedure in CF or is there something I should have done differently?

david.herder
01-10-2011, 04:38 PM
Everything that you did was 100% on the money.

When you measured the response of your uncoated press condition, ColorFlow creates a color model, or some geeks call it a "forward model", of that measured condition. This model is represented by the inner stroke of the PCO element.

There is a stroke that surrounds that press condition as well. This represents the PCO color response. So, when ColorFlow computes curves, it takes the "inner" press condition's color response and transforms it to the "outer" PCO color response. This is what happens when you select a Target in the Simulation dialog. The by-product of this color response is represented by the PCO ICC profile, located directly to the right of the Simulation (target icon).

When you make an adjustment to the PCO color response as you have done, you are updating this color response and as such, a new PCO ICC profile is created automatically for you.

Furthermore, when you create a DVL for your KPS proofer, the source space will be the PCO color response (your press aimed to beta uncoated GRACoL with adjustments) and the destination will be your proofer response.

This is the beauty of ColorFlow: any time you modify the simulation, the DVL will get recomputed automatically.

regards,
dave

jstotz
01-10-2011, 04:55 PM
If I look in the GRACoL uncoated beta dataset it says that the Lab values of the magenta are 55.66, 61.23, -1.08. Lets say that I read my press sheet and I see that the LAB values of magenta are 56.3 70.1 and +.5. This is because I'm printing "better" than the GRACoL uncoated beta standard. The same would be true of the other colors, the solids, traps, and all the interior colors. When CF builds the PCO icc profile I would assume that it's only using the original GRACoL uncoated beta info and I would assume that's what the proof would like. What I want to do is read the final press sheet and load that data into CF so it will make the proof look like my "better" press sheet.

david.herder
01-10-2011, 05:23 PM
When CF builds the PCO icc profile I would assume that it's only using the original GRACoL uncoated beta info and I would assume that's what the proof would like. What I want to do is read the final press sheet and load that data into CF so it will make the proof look like my "better" press sheet.

No. When CF builds the PCO ICC profile, it is not just the GRACoL uncoated data that is being used. It is the color response of your press aimed at the GRACoL uncoated data. This is the critical difference. So, the profile that is generated for the PCO is that of your press tuned to the GRACoL uncoated dataset, not just the target of GRACoL uncoated.

Just to prove this out, create two color setups:
Color Setup A
PCO = CMYK Reference with GRACoL beta uncoated as response
SCO = your KPS proofing condition

Color Setup B
PCO = CMYK Reference with your exported PCO profile from your current GRACoL uncoated color setup
SCO = your KPS proofing condition

The proof output from Color Setup A will look like your press "tuned" GRACoL response. The proof output from Color Setup B will look like GRACoL uncoated (which doesn't mean much visually, but you can compare numbers against the dataset).

Now, if you don't WANT the press to look like GRACoL uncoated, and truly want the native response of the press (not aimed at GRACoL uncoated), then select Simulation = "None" in the Simulation dialog and you will get the uncalibrated response of your print condition. I don't think this is what you want, because I think you still want to control gain, its just that your primaries and secondaries are cleaner than the target dataset.

My recommendation is to run with your current color setup with press aimed at beta uncoated GRACoL as PCO. The fact that you are getting a bit better gamut volume is a bonus. The main thing is to control gray balance.

dave