Linear calibration

[saint]

I just completed a 4 color linear calibration and have noticed that our Magenta is running hot and blues look purple.

Should I be adjusting the curve after I input the linear calibration numbers or should I just run with what the halftone reading says?

I did the calibration twice and got the same results on both 300lpi and FM screening.

Does anyone have a suggestion?

 

[gordo]

I just completed a 4 color linear calibration and have noticed that our Magenta is running hot and blues look purple.
Should I be adjusting the curve after I input the linear calibration numbers or should I just run with what the halftone reading says?
I did the calibration twice and got the same results on both 300lpi and FM screening.
Does anyone have a suggestion?

"Hot" isn't a very meaningful term.

What ink sequence are you running?
What ink densities are you running to?
What dot gains are you achieving?

What size FM dot are you using?

What is your current standard screening?
What dot gains are you achieving with your current standard screening?

best, gordon p

 

[saint]

"Hot" isn't a very meaningful term.

What ink sequence are you running?
What ink densities are you running to?
What dot gains are you achieving?

What size FM dot are you using?

What is your current standard screening?
What dot gains are you achieving with your current standard screening?

"Hot" isn't a very meaningful term. The magenta in the print is heavy even when I am at density. Flesh tones are heavy. Reds are over saturated when I am at densities of CMYK.

What ink sequence are you running? K-C-M-Y
What ink densities are you running to? I use a greytag densitometer so believe we use C-145 M-154 Y-100 K-180 ( I will confirm in the morning as I am recalling densities from memory)

What dot gains are you achieving? I don't know

What size FM dot are you using? 16 micron

What is your current standard screening? 300 and FM

What dot gains are you achieving with your current standard screening? I don't know

 

[gordo]

What ink sequence are you running? K-C-M-Y
What ink densities are you running to? I use a greytag densitometer so believe we use C-145 M-154 Y-100 K-180 ( I will confirm in the morning as I am recalling densities from memory)
What dot gains are you achieving? I don't know
What size FM dot are you using? 16 micron
What is your current standard screening? 300 and FM
What dot gains are you achieving with your current standard screening? I don't know

I'm trying to understand what the problem is that you are trying to fix.
If 300 and 16 micron FM are your current standard screening - then, is the problem that the Magenta has suddenly started printing darker/more dot gain?
Were you using plate curves before with those screens - and presswork was OK? If so why did you do a linear calibration?

Using 300 and 16 micron FM will result in more dot gain than running, for example, 175 lpi with linear plates. That increased gain can be compensated for with a curve applied to the plates. The process is very deterministic but you need the numbers (SIDS, dot gains, etc.)

best, gordon p

 

[Lukas Engqvist]

Is the magenta darker on just one paper type? When deciding on your target values you must look at full density of primaries AND secondaries. If 100C 100M is too purple linearising can do nothing about it!! You will either have to adjust your densities or change inks!

We find some paper types are very sensitive to dot gain in magenta. To me tha magenta looks high. To be able to use the same ICC profiles for different paper stock we find that just varying the magenta on the less coated we may have to decrease magenta to from 150 to 140. In some instances we have even seen the need to do this from sida A to side B beacause of the papers unevenness. I would susspect that at higher screen this would be even more of an issue. (we will sometimes just throw in different stock, and advantage of sheet fed, to confirm that it is a substrate issue)

One more thing that we tried with a particular job we were having trouble with (beacuse of the particular paper) we solved by switching to low-tac ink on magenta.

These are just some experiences (to do with real world solving the problem) and may not be relavant to your process. Don't missunderstand me I am all for going by the book as far as possible, especially when creating the curves.