HowTo lower the black channel in a profile?

[DragonLeaves]

Greetings,

My turn to ask a question :-)

I have a request to lower the black channel in a profile created with CPS.
I know that this can be done.

Background: On a Color Press, on a felt 300 gsm, the dark areas of a jpeg are too glossy. We need to reduce gloss by reducing the darkness, in this we'll do the K channel I presume, in the profile. We saw that in less dark areas that there is less gloss.There is simply no tutorials on Fiery Profile Editor that I could find, so I am asking for some help here.

Any pointers are welcomed!

[oxident]

Are you sure, gloss is reduced by substituting K with CMY? On my machines, the opposite happens ;-)

[DragonLeaves]

Are you sure, gloss is reduced by substituting K with CMY? On my machines, the opposite happens ;-)

Hi Oxident,

My colleague reports that lighter areas have less gloss on that stock.

Any ideas?

[oxident]

Well, in that case, have you tried adjusting the GCR values while creating a new profile? I guess, this would change black generation a lot. But I'm still curious about that observation...

[Lou_P]

Hi, sorry for my slow reply.

All presses differ about what causes gloss. Sometimes the smoothest darkest shadows look better with more CMY and other times with less CMY and more K only. I'm going to guess this is the case here. Here is how I would set the K:

1. In the profile settings window, pick the factory profile at the top for the ColorPress, similar paper to what you are using (maybe "heavy coated")

2. Go in to edit the K settings. Set max K to 100 if the factory profile didn't set it there. Now enable the option called CMY K Ratio. Set it to 0%. This should result in a K only shadow point.

3. Build a profile and try it.

If you still see the problem go re-make the profile (Use load measurements option and load the other test profile you made so you don't have to print and measure again). This time set the ratio to 100%. Does this one look better? Comparing the 0% (if it didn't work) to the 100% will at least tell us if this is the source of the glossing. Let me know if this does not work and we can try some other adjustments.

~Lou