LAB targets for screens

[Nishanth]

Hello everyone.

I have the Lab targets for the solid colors. By this, can I determine the Lab targets for different percentages?
That is, how can I get the LAB targets for different colors printed as screens. Is there any procedure or formula for this?

 

[disbellj]

1. Open Photoshop.
2. Open color settings:
a. Use your output profile (e.g. GRACoL2006_Coated1v2) as CMYK profile.
b. Choose Absolute Colorimetric Intent instead of Relative Colorimetric Intent.
3. Open Info palette, go to options and set Second Color Readout to Lab Color. (I leave the first color readout to actual color).
4. Open a CMYK file, and take a reading of an area of interest. It should give you the PRINTED Lab values of those CMYK values.

Remember to set your color settings back to what you usually have once done. You do not want to use Absolute Colorimetric Intent to convert Lab or RGB to CMYK, since when using Absolute Colorimetric Intent, paper in the source actually becomes dots on paper in the destination CMYK. Absolute Colorimetric Intent is good for proofing sometimes to simulate paper of the source on the destination when the proofing paper is not close to the press paper, for instance.

Regards,

Don

 

[TerryWyse]

Spot or Process?

Spot or Process?

Hello everyone.

I have the Lab targets for the solid colors. By this, can I determine the Lab targets for different percentages?
That is, how can I get the LAB targets for different colors printed as screens. Is there any procedure or formula for this?

Getting L*a*b* values for CMYK screens is easy as Don pointed out.....but I suspect you're looking for L*a*b* values for spot color tints. The answer is "no". While the L*a*b* for solid Pantone colors are more-or-less well defined, there's no specifications that I'm aware of for what the tint values should be. Having said that, it makes sense to me that Pantone tints should have equidistant dE spacing ("linear dE") relative to the solid L*a*b* value. Whether a press is actually going to behave that way without a compensation curve is another matter.

Terry

 

[martin.weberg]

If you mean spot colours there's no easy way. It would require spectral data and advanced algorithms. See: "http://cias.rit.edu/~gravure/tt/pdf/pc/TT8_Predicting Spot-Color Overprints.pdf" for a related study.

Martin Weberg

 

[disbellj]

Martin,

That paper was intriguing to me. Man you gotta love math, am I right? This shows it is possible to improve what is seen in PhotoShop and other applications when it comes to predicting spot color overprints in tinted areas. Now that we have standards for each paper type 1-5 (with the exception of paper type number 4, but that also is in beta at least, and it looks good to me), this should be something that could be done done to give at least a close preview (like the author said, for practical purposes) of what to expect. Nice. Thank you for sharing.

Regards,

Don

If you mean spot colours there's no easy way. It would require spectral data and advanced algorithms. See: "http://cias.rit.edu/~gravure/tt/pdf/pc/TT8_Predicting Spot-Color Overprints.pdf" for a related study.

Martin Weberg