Offset Press Calibration CMYKOG

[indy jones]

What is the process for calibrating for Orange and Green on offset press? We have Curves 3 to calibrate. We have our press calibrate to Gracol 2006 and XCMYK. Any good pdf for quidance?

 

[indy jones]

I found in the internet a p2p27x chart for Curves 3 for Orange, Green And Violet in place of Cyan, Magenta and Yellow. Cannot find it anywhere. It is mentioned in Chromix website in ColorWiki.

 

[indy jones]

I am think of use Gracol 2006 aim points with Curves 3 with g7 curves with orange and green inks on press.

 

[indy jones]

I know this a big subject to talk about.

 

[gordo]

Could you post pics of the dot gain/tone curves for each of the process colors? Why O and G? What ink are you using - i.e. are you using PMS Orange and Green? Did you just ask your ink supplier for the ink hues that you're thinking of using? What screening are you using?

 

[indy jones]

We are new to this Hexachrome setup. Orange and Green because we have an Epson 9000 with Orange and Green ink setup. We are hoping to calibrate the press and create an icc profile to see if we can match our press. I am open for what Orange and Green ink to use. Screening Conventional and FM.

 

[gordo]

We are new to this Hexachrome setup. Orange and Green because we have an Epson 9000 with Orange and Green ink setup. We are hoping to calibrate the press and create an icc profile to see if we can match our press. I am open for what Orange and Green ink to use. Screening Conventional and FM.

You need to make sure that the inks used for the O and G are designed to run as "process" colors (i.e. be screened and wet trapped). This is a major point of failure in EG printing and can be exacerbated with FM screening. The below are some examples - your results may appear different. The key is that the integrity of the ink lay down should be similar to your process ink lay down (assuming the your process printing is as it should be).

On the left is a solid O ink formulated correctly and on the right a solid O ink incorrectly formulated:

A screened area of the O ink incorrectly formulated:

There are several methods that printers use to build a dot gain curve for extended process colors:
1) Use the Black curve
2) Use the curve of the closest process ink hue (in your case the Cyan curve)
3 Build a curve the conventional way (target curve plus press response = compensation curve)

A fairly common ink hue for O is PMS 151 and PMS 7481 for green.

You should also confirm how your RIP assigns screen angles. With AM screening some RIPs simply assign the Black angle to any channels more than 4, others cycle through the KCMY angles over again. With FM you should see if there are screen patterns specific for channels beyond CMYK or how it handles those extra channels.

 

[indy jones]

Thanks Gordo for your response.

 

[DeltaE]

You need to make sure that the inks used for the O and G are designed to run as "process" colors (i.e. be screened and wet trapped). This is a major point of failure in EG printing and can be exacerbated with FM screening. The below are some examples - your results may appear different. The key is that the integrity of the ink lay down should be similar to your process ink lay down (assuming the your process printing is as it should be).

On the left is a solid O ink formulated correctly and on the right a solid O ink incorrectly formulated:

A screened area of the O ink incorrectly formulated:

There are several methods that printers use to build a dot gain curve for extended process colors:
1) Use the Black curve
2) Use the curve of the closest process ink hue (in your case the Cyan curve)
3 Build a curve the conventional way (target curve plus press response = compensation curve)

A fairly common ink hue for O is PMS 151 and PMS 7481 for green.

You should also confirm how your RIP assigns screen angles. With AM screening some RIPs simply assign the Black angle to any channels more than 4, others cycle through the KCMY angles over again. With FM you should see if there are screen patterns specific for channels beyond CMYK or how it handles those extra channels.

WOW, it is good to read this response!

 

[indy jones]

Does it make since to get ink hue from our Epson 9000 which has orange and green ink and match for our press orange and green?

 

[gordo]

Does it make since to get ink hue from our Epson 9000 which has orange and green ink and match for our press orange and green?

Generally the choice of press EG process ink hues is based on the print buyer's use of color. I.e. it makes no sense to use O and G if the buyer primarily specifies Blues and Purples. Also Green is not used as much because it is not particularly much out of gamut compared to C+Y.

You might start with determining the gamut of your CMYKOG proofer vs your CMYK press and the hues of your proposed O and G inks. And yes, trying to find press O and G inks that are similar to your proffer's O and G hues can help align press and proof. But as long as the proofer gamut is greater than the press you should be able to align the two.

PS don't forget to check the OBA content of your proof paper (which tend not to have OBAs) vs the press paper (which tend to have OBAs).