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chromatic vs achromatic GCR settings

Offline MaxGamut Posted 09-01-2016 - 07:37 AM
Post: #1
Member
21 Posts
Member

Onyx Version:
10
Printer(s):
HP L26500, Canon iPF9000

Hello gentlemen.

I once again would like to ask my "favorite question". Onyx Help is quite short, not very clear and explanatory.

I´m perfectly familiar with standard GCR settings - afaik this corresponds to achromatic black GCR settings in Onyx, and is common and clear everywhere. But ... the more I think about it the less I understand the chromatic black GCR settings in Onyx, which is different from other profiling software I know. (PM5 has the "Black width")

Please, can anybody explain what do the settings for chromatic black stand for?
What is the "gray component" there? Can somebody give some numerical example?
I also do not understand what does the Black start and Max black mean here? Like - Black start 40, what does mean 40% for CMY and for K in that chromatic settings?

Thank a lot for your time !!! Smiley
(This post was last modified: 09-05-2016 02:33 PM by MaxGamut.)
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Offline Pauly Posted 09-02-2016 - 08:41 AM
Post: #2
Frequent Flyer
109 Posts
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Onyx Version:
12.0
Printer(s):
Oce Arizona 480XT

Achromatic - How much K (Black ink) is used instead of CMY in grey scale images or black and white. So if you start black at 40%. any greys under 40% will be CMY with no K. anything above 40% will start to use K

Chromatic - Would be Black width. IICR start k 50% would be the same as setting the black width at 50%. With the option of choosing a curve and limiting how much K you would like to use as maximum.
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Offline MaxGamut Posted 09-05-2016 - 03:57 PM
Post: #3
Member
21 Posts
Member

Onyx Version:
10
Printer(s):
HP L26500, Canon iPF9000

Thanks for answer, Pauly. But "would be..." is of no use for me. I need to solve "waving media" problem on a Latex HP - I need to tweak everything to the last %.

Let´s see first, if we understand the terms in the same way.
- Black Width in PM5 does not correspond to Black Start in any GCR, as it has completely different logic. (looking at lightness, Black Start is working vertically, while Black Width horizontally)
- GCR is not for gray-scale images or B/W images, but for any images and any colors with a gray component.

Example to discuss:
GCR Start=30 means - replacement of any weighted combination of CMY starts at say 40/30/30/0 ... 60/50/50/0 will be replaced with approx. 50/40/40/10 or 30/20/20/30 - depending on how steep the GCR curve is.
Then there are chromatic colors - what happens to 100/40/40/0, whether it will be transformed to 60/0/0/40, or to 80/20/20/20, and how far to go from the gray axis is set by Black Width (in PM5).

But how does it work in Onyx? Is the chromatic GCR the opposite side of the standard GCR - GCR for the chromatic colors?
If so, why do they call it Chromatic Black settings and Achromatic Black settings instead of "GCR setting for chromatic/neutral colors"? I simply see not much black or gray on a darker red like 40/100/100/0. Wink What can I expect here to be introduced - chromatic or achromatic black GCR? Will the red be transformed to 30/90/90/10 or so? Probably yes.

Then - dark violet-blue 100/100/30/0 will not be transformed? This color is quite dark - I would like to have an option to replace much earlier and much more... like replacing everything from 50/50/0/0 and up with black channel (because in facts 50/50/0/0 has the density similar to 50/50/50/0)
How can I set GCR in such case? GCR Start =0? What about other colors in such case, what about dark yellow 20/20/100/0? GCR start=0 is totally unsuitable as it would introduce 20%K into yellow !

So how can these separate settings for chromatic black (chromatic colors) help me? In what cases can I use them with some success, and how? Is the Black Start setting really the grey component value where K-channel should start?
(This post was last modified: 09-07-2016 03:26 PM by MaxGamut.)
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Offline Pauly Posted 09-05-2016 - 07:21 PM
Post: #4
Frequent Flyer
109 Posts
Frequent Flyer

Onyx Version:
12.0
Printer(s):
Oce Arizona 480XT

I have not had the best experience with onyx ICC engine to have been playing around with their GCR settings.
I've been using basiccolor print and have been getting amazing results.

What i'd do, is make many iterations of the profile.
For example I would put:
Achromatic: start black on 0, maximum on 100, Black generation: Max
Chromatic: black generation on No K (it turns it all to 0 or off)

Then the next profile, i would start black at 25. leave the rest the same. 3rd profile on 50, then 100

so you'll have 4 profiles with different start blacks on achromatic black.

Then i'd Turn K off for Achromatic so in the black generation go to No K.
Chromatic settings start black at 0, max at 100 on max black generation. Then go up by 25 again.

So now you'll have 8 profiles.

Go into job editor, open your vivid chart. go to your colour correction and turn all colours off except black. go back to printer and media and go through the 8 profiles and you'll see what onyx does with the black inks.
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