Help! Greys look green!

[BrentNaquin]

I’m running into an issue with my printer where every gray I try to print comes out with a greenish tint. I’ve already done a paper feed adjustment, tried different printer profiles, and even manually adjusted the colors in my files. No matter what changes I make, the grays refuse to print as true neutral grays — they always have a green cast.





Has anyone else run into this problem, and if so, what solutions worked for you? I’m trying to get consistent, accurate gray output without the unwanted color shift.

 

[Solventinkjet]

It’s a very common issue in digital printing, and the simple answer is linearization. Printheads aren’t perfectly uniform, neither between different units nor within the same one over time. Their output drifts due to factors like ink formulation, environmental conditions, and general wear.

Ideally, a printhead would deliver exactly the color percentage you specify. If your design calls for 50% magenta, it should print 50% magenta precisely. In reality, that rarely happens, especially in the mid-tones, where printed values often deviate, typically on the low side. That’s why poor linearization tends to reveal itself most obviously in grays: you might send 50% CMYK, but the printer actually lays down something like 44%C, 52%M, 57%Y, and 49%K, resulting in a color shift or tint.

Linearization brings those values in line, pun intended. It involves using a spectrophotometer to measure the actual printed values so the RIP can compensate and bring output back into balance.

Short of that, you’re left manually tweaking CMYK values or experimenting with density curves in the RIP.

 

[BrentNaquin]

I don’t design in CMYK. I design in RGB due to fellers support telling me that’s fine because these printers (mutoh Xpertjet) are just big desktop printers now. All the other colors seem to be closer when I design in RGB. Like black, I can only achieve good black with 0,0,0 RGB. I’ve tried with CMYK and nothing looks as good as 0,0,0 RGB.

With that being said, could this be causing some of the issues I am having?

Also, I can’t get one of those machines and my company is too cheap to get a professional out. I’ve explained 100’s of times that this problem is too complex for me. So am I right to think that this may not go away? If I play with these curves in RIP, will that change everything?

We have clients that may come back and want something printed due to damage, if I make these changes, won’t that change everything?

 

[BrentNaquin]

By the way I have tried tweaking CMYK and RGB values to fix grey. Nothing works.

 

[Solventinkjet]

Even though you're designing in RGB, the RIP still converts it to CMYK and then the same issue happens where the actual output isn't matching what the RIP tells it to print. It's fairly common to design in RGB and that shouldn't be the cause of the issue.

I'd say about 80% of sign shops don't linearize for the same reason. The equipment is expensive. If you go to any large sign shop or wholesale printer, they're all using spectros as a regular part of their process.

Yes, changing the curves will change everything and it will be harder to reprint the same color from a previous job. That is also something linearization fixes, color consistency over time. Linearization is more of a maintenance function rather than a one time fix.

Hopefully other people can chime in with their fixes. I'm more on the technical side and don't have to deal with issues like these on a daily basis. And like I said, this is a very common issue. Many people have little work arounds that get them at least closer to better grays.

 

[Gino]

Not sure if I have this worded properly, but just about all rips will print cmyk and when receiving rgb will convert them over anyway. The conversion processes all tend to do their own prefixed job. I rarely work in rgb, only because it doesn't rip 100%.

 

[Jharris81]

Did this just randomly start happening or did you get a new printer or how did this come about?

 

[Nanci]

I have manually made a few dozen grays and label them accordingly: cool gray , medium warm gray,etc. I printed them out so I can reference them since what they look like on the screen is so completely different. This thread caught my eye because I had this problem a few years ago when my magenta was dropping out and this is what made me realize it.
I think you can manually design a few grays you like. Start with Pantone color palette. That has worked well for me.

 

[cornholio]

While Solventinkjet has written about what it's all about, I'd like to add some thoughts from the field.
Thermal heads like HP are much less stable over their lifetime, than piezo heads. That's why HPs have a integrated linearization (CLC).
Next is the age and/or the agitation of the inks. If the ink sits in the cartridge for a prolonged time, it starts to demix. Depending on the ink, or even the color, this takes from a week(white) to a year or so.
So when a customer complains about color shifts in piezo printers, my first question is: how often do you replace ink carts? If he replaces 3-4 times a year, he should be ok from that aspect. If not, do you shake them regularly?
If inks have been demixed to a certain level, only replacing the carts makes sense.