GRACoL 7 - spectro with UV at end of name

[meddington]

Originally Posted by disbellj

Only one will give me the correct reproduction of the light color. Which one is it?

That's the thing about optical brighteners...both uv included and uv excluded measurements could be skewed. For sure Fogra39 and GracolCoated1 data sets represent "full spectrum", unfiltered measurement (and I support the idea of verfification with unfiltered devices), but these data sets also represent a paper with moderate OB content. If your paper has robust OB content, either UV included or excluded may yeild misleading results. Also consider that there is no consideration given to the ambient lighting conditions in which the proofs/press sheets are viewed, which may excite the OBs in a manner different from the spectro. In short, OBs throw a wildcard into the mix for which there is as yet no firm answer to the UV filtration question. Therefore, the best solutions to the OB problem usually involve some subjective analysis...Xrite's Optical Brightener Compensation module for instance.

[disbellj]

Michael,

I don't know what to say except thank you for your post and it would be great if there was less confusion. I've already went back and forth enough with my boss on this, and I'm about to throw my hands up and say screw it.

Thanks.

Don

Originally Posted by meddington

That's the thing about optical brighteners...both uv included and uv excluded measurements could be skewed. For sure Fogra39 and GracolCoated1 data sets represent "full spectrum", unfiltered measurement (and I support the idea of verfification with unfiltered devices), but these data sets also represent a paper with moderate OB content. If your paper has robust OB content, either UV included or excluded may yeild misleading results. Also consider that there is no consideration given to the ambient lighting conditions in which the proofs/press sheets are viewed, which may excite the OBs in a manner different from the spectro. In short, OBs throw a wildcard into the mix for which there is as yet no firm answer to the UV filtration question. Therefore, the best solutions to the OB problem usually involve some subjective analysis...Xrite's Optical Brightener Compensation module for instance.

[disbellj]

Michael,

Put it like this:

GRACoL 7 is being sold to printers as easy to set up to. I have talked for around 5 years on and off - to try and get my boss to move to GRACoL (heck, even while it was still in beta).

They finally decide to make the move, and I'm seeing problems before we even start. Why? Has there not been enough time to figure these things out, or is it apathy?

On one side, I have a boss who would rather get the free stuff from the vendor. On another side, I have GRACoL tauting (and others now too, such as X-Rite and other vendors) easy setup/verification. I would love to get a G7 Expert in here, but they won't do that I'm sure. It's getting easier for me to just say forget it and stay with what we're doing. Visually it's close enough my boss hasn't decide to move to GRACoL no matter how much I asked before now. Now that he's willing, there are still things that sound like it's not as easy as what it is advertised to be (and to think I 'm actually surprised, although I know I shouldn't be).

Regards,

Don

Originally Posted by meddington

That's the thing about optical brighteners...both uv included and uv excluded measurements could be skewed. For sure Fogra39 and GracolCoated1 data sets represent "full spectrum", unfiltered measurement (and I support the idea of verfification with unfiltered devices), but these data sets also represent a paper with moderate OB content. If your paper has robust OB content, either UV included or excluded may yeild misleading results. Also consider that there is no consideration given to the ambient lighting conditions in which the proofs/press sheets are viewed, which may excite the OBs in a manner different from the spectro. In short, OBs throw a wildcard into the mix for which there is as yet no firm answer to the UV filtration question. Therefore, the best solutions to the OB problem usually involve some subjective analysis...Xrite's Optical Brightener Compensation module for instance.

[meddington]

From the standpoint of G7 itself, I have are it occur that plate compensation curves derived from uv included and uv excluded i1 pro spectros yielded nearly identical curve results, despite dignificantly different CIELab values. Essentially the measurements with uv filtration were all skewed in the same direction, and since heat balance is based on the white point measurment, the curve recommendations were the same between the two. I wouldn't say this would always be the case, but it was indicative to me that the process would work despit differrences in instrumentation. This would be applicable to colormanagement as there is a mapping from one tristimulus value to another, but for curve creation, there's a bit more forgiveness for the optical brightener issue.

[disbellj]

Michael,

You obviously know more about this than I do. If it works fine when using G7 and either, I guess that's good.

I have just seen where the paper simulation on proof using UV in its proofing rip might give a better paper simulation if non-UV-filtered instrument is used to verify vs. using non-UV-filtered for both, but ultimately my proof failed in the IPA RoundUp I believe for this particular reason.

And for matching light colors, it hasn't for me (because all I've had access to for years is UV filter spectro). Darker colors matching? Not much of a problem. But supposedly the light colors matching is what this was all about - to give same NPDC for all different printing conditions and papers. But obviously NPDC matching doesn't mean colors matching, right? You said same NPDCs, way different Lab values! WTF?! So which Lab values do I put in PhotoShop to convert to CMYK values most likely using Absolute Colorimetric Intent so I can get a color match? One or the other, or do I have to still do tweaking to make some CMYK color recipe in-between that might be right? So I still need a custom press profile and can't use the official profile?

Using one of my existing "GRACoL2006_Coated1v2" CromaPro proofs (where UV-filtration WAS NOT used to make the source characterization data and ICC profile, but WAS used for proofer calibration, profiling, and building of device-link aka "Match" using official GRACoL ICC profile and custom proofer ICC profile), the yellows are to yellow and the grays are too yellow. And the report I got back from that RoundUp 2-3 years ago showed this numerically.

Maybe Dan Remaley was right years ago. I would have been fine staying with densitometry if an ICC profile could have been made for the different paper types, so that everyone can be on the same page concerning expectations, with the added benefit that an ICC profile provides the designer with knowledge of what the finished product will look like while soft-proofing during the design stage. Because frankly, if we all need custom ICC profiles for designers to use, or have to convert incoming SWOP CMYK to custom ICC profile for this to work, then this is not what I thought this was intended to be at all. My expectation, as others, is that the same appearance will be achieved between printers that both use G7. We could all use existing SWOP images, and colors would match between printers.

If we are getting "significantly different Lab values" with the same ISO paper type, and ISO inks hitting ISO solid Lab values, and the NPDC is almost the same, then what does this say about the process and/or the devices used? Were any spectros used during the beta period that had UV filtration? If not, why has it become acceptable to use these instruments? What's the benefit? I can already start to see the problems when you state "significantly different Lab values", which helps none whatsoever in prepress and color matching.

BOTTOM LINE TO ME:
It should be as easy as scanning a printed piece or proof with a color spectro, and doing a conversion to CMYK (the same as everyone would do, so this could actually be done in the spectro software), printing the CMYK values given, and reproducing the color (with the knowledge of the exception that a vibrant color can't be achieved on uncoated paper with just CMYK). If I can't get a color match in my workflow using the official profile at all stages, then this I consider to be a problem. I should be able to use the official profiles for everything, and not have to make a custom profile to get accurate color reproduction. If I still must do that, then IMHO it misses the whole point of doing this in the first place.

Regards,

Don

Originally Posted by meddington

From the standpoint of G7 itself, I have are it occur that plate compensation curves derived from uv included and uv excluded i1 pro spectros yielded nearly identical curve results, despite dignificantly different CIELab values. Essentially the measurements with uv filtration were all skewed in the same direction, and since heat balance is based on the white point measurment, the curve recommendations were the same between the two. I wouldn't say this would always be the case, but it was indicative to me that the process would work despit differrences in instrumentation. This would be applicable to colormanagement as there is a mapping from one tristimulus value to another, but for curve creation, there's a bit more forgiveness for the optical brightener issue.

[rich apollo]

I see the UV cut devices being used more in the proofing arena. So many papers with HUGE amounts of optical brighteners.

UV or non-UV, you'll be able to set up the NPDC. The tricky part that I've seen is trying to set gray balance with a UV-cut spectro. However, if you're running paper without optical brighteners it shouldn't be a problem.

[disbellj]

Rich,

The thing is, we do have optical brighteners in the paper (but we don't run UV inks on press). And as has been pointed out, maybe NPDC can be achieved with spectro with UV filter or no UV filter. But my problem I've seen (because all I've had access to was UV filtered spectro) is that the grays are too yellow, the yellows are too yellow, I can't match light colors whether using Relative Colorimetric Intent or Absolute Colorimetric Intent, I can't validate to the specification, and my proof failed the IPA Proofing RoundUp. So I see the problem as UV filtration, because what else is there? Official GARCoL2006_Coated1v2 ICC profile used, so problem is not there. I believe the problem is that the official profile I'm using has Lab values that were obtained without UV filtration, yet the proofer calibration has Lab values obtained through spectro that has UV filtration, and then those two profiles get "married" into a devicelink where one profile basically uses UV filtration and the other doesn't.

I can easily see that the Lab values obtained from a printed piece (using a spectro with UV filter) is the problem: Obtaining the Lab values using UV filtration, for printing on a printing condition that does not use it. This means the color obtained is wrong in the first place (since UV filter is used, the spectro is not really seeing the color correctly, the Lab values are "filtered"), and I can't expect it would look like the original printed color since the printed color was never really "seen" by the spectro correctly in the first place. So reproduction is not going to look right, especially on a device that doesn't use UV filtration (captured using UV-filtered, printed to non-UV-filtered). I've used Absolute Colorimetric Intent as well as Relative Colorimetric Intent, and light colors don't seem to want to reproduce for me.

Regards,

Don

Originally Posted by rich apollo

I see the UV cut devices being used more in the proofing arena. So many papers with HUGE amounts of optical brighteners.

UV or non-UV, you'll be able to set up the NPDC. The tricky part that I've seen is trying to set gray balance with a UV-cut spectro. However, if you're running paper without optical brighteners it shouldn't be a problem.

[meddington]

Originally Posted by disbellj

Rich,

The thing is, we do have optical brighteners in the paper (but we don't run UV inks on press). And as has been pointed out, maybe NPDC can be achieved with spectro with UV filter or no UV filter. But my problem I've seen (because all I've had access to was UV filtered spectro) is that the grays are too yellow

A partial solution to the issue with regards to press calibration is to augment the white point when determining gray balance adjustment. In Idealink Curve, this can be done by adjusting the gray aim point, using "Custom White" and and manually setting the a*, b* values to a value that will push gray balance in the direction desired. For a UV filtered device, this might mean a lower b* value than you measured. This is largely subjective, and perhaps hard to hit on the head the first time, but it could allow fine tuning the NPDC and gray balance with a UV filtered device. Same could be applied for a non-filtered device on a paper with significant OB content, only you might raise the b* value in this case.

From a proofing/color management perspective, its more complicated, though white point editing can also improve the issue.

[rich apollo]

You can also use a densitometer to set the gray balance. Include one of Don Hutcheson's old Gray Finder targets on the test form. Measure the patches with with all filters on. Neutral is the patch at which the filters all read equal. The target tells you the adjustment to make.

[disbellj]

Thanks Mike.

I guess Kodak will come in and do what they do.

Whether I can be sure that their verification is going to be correct is in doubt.

Guess there's no way for me to double-check except for soft-proofing to make sure soft-proof using official GRACoL2006_Coated1v2 ICC profile (where my screen is less than 1 dE during calibration and profiling) matches the GRACoL proof and press sheet. If not, that would be a red flag to me.

Regards,

Don

Originally Posted by meddington

A partial solution to the issue with regards to press calibration is to augment the white point when determining gray balance adjustment. In Idealink Curve, this can be done by adjusting the gray aim point, using "Custom White" and and manually setting the a*, b* values to a value that will push gray balance in the direction desired. For a UV filtered device, this might mean a lower b* value than you measured. This is largely subjective, and perhaps hard to hit on the head the first time, but it could allow fine tuning the NPDC and gray balance with a UV filtered device. Same could be applied for a non-filtered device on a paper with significant OB content, only you might raise the b* value in this case.

From a proofing/color management perspective, its more complicated, though white point editing can also improve the issue.