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Eliminating greens in black gradient prints

Offline Pauly Posted 09-16-2015 - 03:49 PM
Post: #1
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Onyx Version:
12.0
Printer(s):
Oce Arizona 480XT

Hey members, I am new here, but i've been a lurker for a while.

I've came across an issue when i print black gradients, in the sunlight/daylight it looks a little green. Ive read that it's a common? thing as black generation using 3 colours to make black ect. I know solutions is to pull magenta but i want to avoid that.

Anyway my main media is Glass so at the moment that's what i've noticed it more on.

I do my own profiling and i do understand the colour generation on large format printers isn't 100% perfect specially blacks and red at times.

So if anyone can shed a little light onto how to remove the green look from the black would be brilliant.

I would assume it would be somewhere in the Advance ICC Build settings?

Only issue i have is that i cannot just try a setting and print it, check and adjust as the process takes a day to view results.


Printer: Oce Arizona 480
Rip: Thrive Rip-Queue 10.2.5.45
Spectrophotometer: Barbieri Spectro Pad

Thanks.
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Offline virtu Posted 09-18-2015 - 02:13 AM
Post: #2
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Onyx Version:
10.2.5
Printer(s):
Spuhl virtu RS-35, Canon ipf9100, HP5000, RS-640

Is turning off icc and printing only with black an option ?
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Offline Pauly Posted 09-18-2015 - 11:52 PM
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Onyx Version:
12.0
Printer(s):
Oce Arizona 480XT

Unfortunately it's not an option. i need the ICC on. printing only black will give gradations and not enough depth.

I'll be upgrading to x12 and see what i can do from there.
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Offline Mikulas Posted 09-21-2015 - 11:04 AM
Post: #4
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Onyx Version:
10.2
Printer(s):
L26500, W8400+Onyx / Mimaki JV4, JV5 +TexPrint

Hello from Vienna Pauly!
This is a bit more complicated question. A bit of spectro-science needed!!!

1/ Off-topic, but necessary - I can understand "graining" in light grey tones, but why do you have gradation steps when printing black only? This is definitely not a good starting point! Sad I have seen many PDF´s and EPS files with poorly made gradation-objects (not full 255 steps). Cannot this be the problem?
1a/ Not enough density? K should usually give the best density... Is it some special technology what you are talking about?

2/ Color casts in grey vs. light source - this one is a VERY COMPLEX one !!! It´s all about light and spectrometry. We all fight years with these problem. In our company every printer has some different color casts depending on light source - Just Normlicht show something grey, under Philips Graphica neons - green cast, daylight purple cast... Eek!Grin
The best "easy answer" you can get is from virtu here- use black channel only. Black is spectrometrically made to be stable = it is most probably neutral under any light source!!! As soon as you involve CMY, you will get problems with metamerism. Many modern "ultra-gamut" inks have huge problems here.
The second best answer is - use stronger GCR level. Replacing CMY with more K could help you get more stabile neutral grey in different conditions.
The third best answer is - go, and get a beer or two... Cool
The fourth best answer is - testing and alchemy !!! Generating different versions of the same ICC profile for every light source... ConfusedGrin
(This post was last modified: 09-21-2015 11:21 AM by Mikulas.)
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Offline virtu Posted 09-22-2015 - 05:24 AM
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Onyx Version:
10.2.5
Printer(s):
Spuhl virtu RS-35, Canon ipf9100, HP5000, RS-640

Then "maxK" is the setting you are looking for. When you create an icc profile you can choose the seperation of the profile. Pick maxK with a start of 0 K, that will use a lot of black in your profile.

Maybe you should have also a look in here:
http://onyxtalk.com/thread-trouble-print...59#pid4859


Good luck.
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Offline Pauly Posted 09-23-2015 - 06:35 PM
Post: #6
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Onyx Version:
12.0
Printer(s):
Oce Arizona 480XT

Thanks for the replies!

Good news is the job is complete with samples sent back and forth eliminating black by adding magenta.

I'll wait till X12 upgrade until i play with the profile (more options)
Are you suggesting to change the light source on the profile from D50 to something else and see?

An issue i've been having is when profiling, the only light option i can use is M0 (tungsten). Each time i tell it to use M1(D50) it'll use it for the first set of patches, then change to M0.

I did try changing the start of black. I use moderate with 45. went to 35 but still had green.


The actual image was all consistent in the RGB colours. R30 G30 B30 for example but in CMYK that was just K.
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Offline Mikulas Posted 09-28-2015 - 02:38 PM
Post: #7
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Onyx Version:
10.2
Printer(s):
L26500, W8400+Onyx / Mimaki JV4, JV5 +TexPrint

Are you suggesting to change the light source on the profile from D50 to something else and see?
- Absolutely NO. That is the most advanced way! Until you have lot lot lot of experience and very good quality ICC profiles (or at least very very accurate measurements) there no reason to try it. It modifies the profile in "strange ways" (of course not strange, but very complex ), and the differences is relatively small.
D50 in many cases is the "most logical average".

An issue i've been having is when profiling, the only light option i can use is M0 (tungsten).
- This is a bit pity. M0 is fine in many cases. M1 is better and more advanced. The reason - optical brighteners (OBA) are everywhere. OK, not everywhere, but in many materials. Sad I have tried M1 with some of our profiles and the results were MUCH better. Especially on textiles where OBA´s are heavily used.

I did try changing the start of black. I use moderate with 45. went to 35 but still had green.

- As told earlier - green cast can have different reasons! I´m now talking only about "how to quickly save problems". If you have some systematic error in the profile or calibration this will only help a bit, but not solve it. The best case you will get is significantly more stable mid-tone greys, but gradations to very light greys will still suffer from color casts. (=you will never get a really nice monochromatic print in this way Sad)

From my head only - European ISO Coated v2 has the black start at 10 or so... Fogra39 (the same spectral data, but profile made by Adobe) has the black start about 15. US standards have the black start a bit higher.
As you can see - your 35 or 45 is very high. Such higher values are used on printers with bright LC+LM (to not spoil pastels), or with poor raster (to enhance smoothness of light greys)

So, my recomendation (and virtu´s too Smiley ):
- use Heavy or Max Black Generation
- start the Black Generation much lower - at 10-20 or even less (if you have the raster small enough)

And the last question (in facts should be the first):
- How strong is your green cast?
Is it clearly a "green-grey" under more that one light source or...
is your grey usually nice and only sometimes very slightly greenish?
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Offline Pauly Posted 09-28-2015 - 03:16 PM
Post: #8
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Onyx Version:
12.0
Printer(s):
Oce Arizona 480XT

We usually try keep the start black between 40-50 as that's how the arizona likes it. Or it's just to dark.

I might wait until i upgrade to onyx x12 or figure out how to use the Barbieri software to create an ICC out of onyx to use more options of the device. Ie D50 light.

The cast isn't strong. Say in the workshop, a little darker. It'll be fine. But as soon as you take it outside you can see the green. On the final print, when added 12p of magenta it was pretty good except the lighter parts of the image you see a bit of a cast.
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Offline virtu Posted 09-29-2015 - 05:23 AM
Post: #9
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Onyx Version:
10.2.5
Printer(s):
Spuhl virtu RS-35, Canon ipf9100, HP5000, RS-640

Hello Pauly,

Mikulas gave you quite the answers you were looking for. Your problem is wrong GCR settings, Onyx12 cant help you in that case.

In addition that that:

K start 40 is good for bright colorful prints.
K start 0 is good for B&W prints.

good luck with your next jobs.
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Offline Pauly Posted 09-29-2015 - 04:10 PM
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Onyx Version:
12.0
Printer(s):
Oce Arizona 480XT

Hey Virtu,

Thanks for that. I'll do some toying around with those settings or similar.

I'm hoping with x12 will be better with using external software (barbieri gateway) a little better than x10 does.

Thanks your everyones help
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Offline Mikulas Posted 09-29-2015 - 05:35 PM
Post: #11
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Onyx Version:
10.2
Printer(s):
L26500, W8400+Onyx / Mimaki JV4, JV5 +TexPrint

We usually try keep the start black between 40-50 as that's how the arizona likes it. Or it's just to dark.
- Dark? Normally should not be. GCR is replacing the grey component with only appropriate amount of K! Let´s say 15/10/10 replacing with 7%K. Stronger GCR should only introduce visible graining into light tones, but no significant darkening. If stronger GCR makes your prints darker it could mean that ICC assumes colors are lighter than they actually are. GCR then starts to push more K into color than necessary.

Reason 1/ could be - your media has significantly higher dot gain than used media profile. (It is hard to distinguish such "bad" linearisation (dot gain problems) with eyes only. Single colors usually look like "a bit darker".)
Quick check - can you compare your 25,50,75% black with some good reference?
Real solution - are you able to do re-linearistation for this media profile? This is a very important step when using generic profiles! As I wrote you earlier - it is possible to use generic ICC profiles with some success, but not with the appropriate linearisation!

Reason 2/ could be - you are using non-standard media with too dark white point (like boards and foams, or printing over some white ink)
This could cause the "dark prints", and is also hard to solve. Needs some biger compromises in contrast/lightness. I have ho real experience with such reduced-gamut media, sorry.
Nevertheless, this would be no reason for stronger color casts.

On the final print, when added 12p of magenta it was pretty good
- If 12p means 12% then ... it´s quite ... Confused ... not correct.
To set scale for further discussion - Now I´m talking about color cast that can be solved by adding 2-3% of C/M/Y in the mid tones.
Is this your case? If not, you definitely need to start with ink limiting and linearisation...

I'm hoping with x12 will be better with using external software (barbieri gateway)
- Do you really need that external software? I´m not familiar with Onyx Thrive. Are there no calibration tools in Thrive?
(This post was last modified: 09-29-2015 05:39 PM by Mikulas.)
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Offline Pauly Posted 09-29-2015 - 06:06 PM
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Onyx Version:
12.0
Printer(s):
Oce Arizona 480XT

When i had the start blacks on 0, all the dark colours where too dark. when put on 45 with moderate generation the print was very accurate to what was on the screen.

My media is Glass. so i do a double strike/density print, then backed off in white (painted)
My major issue is just printing a sample. It takes 2 days to view finished piece. I'm in the middle of changing adhesion promotors so process will be much quicker, but i'll need to profile again. So i'm holding off on testing at the moment. Right now i'm trying to work the software (onyx & barbieri gateway) to read the patches in D50 and not change to Tungsten light.

I don't think it was 12% he did say 12p though. I'm not sure what exactly that means. I'll speak to him when he comes this afternoon.

When using a Barbieri spectro, Onyx opens the correct program (with in onyx) to read the patches. Barbieri uses it's own called Gateway.
So when you go 'read patched' gateway opens, connects to the device and you read the patches though gateway then it loads the date back into onyx.
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