GRACoL2006 M2 Numbers

[Vernon Roberts]

We have a Heidelberg Image Control, and as far as I can tell, it scans in just one mode. I talked with Heidelberg and they say it scans in M2. I would like to put the GRACoL 2006 numbers in there for M2 as a reference for the pressman to use on coated stocks, but don't know what they are or how to get them. Isn't GRACoL2006 M0 numbers? Also, I was told that the Image Control recalculates the reference based on the paper white it gets from the sheet. Does anyone have access to an Image Control and understand how it goes about this. I've created my own reference print conditions in Color Toolbox by using it's convert paper white calculator and recalculating the reference. Does it work in the same way?

 

[gordo]

Why are you set up to measure in M2? M2 is used when the paper fluoresces (which is typical with today's papers), but there's a desire to eliminate this effect from affecting the data.

 

[Vernon Roberts]

Why are you set up to measure in M2? M2 is used when the paper fluoresces (which is typical with today's papers), but there's a desire to eliminate this effect from affecting the data.

I didn't purchase the device, and like I was saying, it's the only way the device scans. I trying to make the best of what we have.

 

[gordo]

I didn't purchase the device, and like I was saying, it's the only way the device scans. I trying to make the best of what we have.

Find out from Heidelberg if your scanner can be modified to scan in M0 or M1.
If you're using solid patches for measurement data then it probably doesn't matter that the device is reading M2 (ink blocks the effect of OBAs).

 

[Deleted member 16349]

If you're using solid patches for measurement data then it probably doesn't matter that the device is reading M2 (ink blocks the effect of OBAs).

Hi Gordon,

I don't see how normal CMY inks can block all of the effects of OBAs. Since all these ink do not block all the transmitted and reflected light in the visible spectrum, I suspect that they also can not block all the UV light. Certainly they could not block all the generated blue light from the OBAs back out to the eye. So UV light would only have to pass only once through the ink film in order to generate the blue light. Passing once through the ink film results in quite a bit more light getting to the print surface than what is normally measured when reflected back to the eye because the light is filtered on both passes.

If I remember right, in some of your past samples of print in only visible UV light, one could still see the image where the ink was placed on the print. If ink would block all the UV light, then those areas would be black.

Maybe it is more correct to say that the ink would block some of the effects. Can you comment.

 

[arossetti]

I mean M2 measurements on a normal offset sheet with -6 or so B* value probably isn't going to make that big of a difference in the color results for this guys plant. If they are going from nothing to something I would just use the M0 GRACoL values as my target.

 

[Vernon Roberts]

Find out from Heidelberg if your scanner can be modified to scan in M0 or M1.
If you're using solid patches for measurement data then it probably doesn't matter that the device is reading M2 (ink blocks the effect of OBAs).

I've heard the optics can be upgraded for something like $70K. I don't know the details of the upgrade, but it's something we aren't going to do. I was just hoping someone had these numbers, or could help me with a way to use GRACoL LAB references at the press with this device. It does seem like Yellow would be affected by OBAs.

 

[gordo]

I've heard the optics can be upgraded for something like $70K. I don't know the details of the upgrade, but it's something we aren't going to do. I was just hoping someone had these numbers, or could help me with a way to use GRACoL LAB references at the press with this device. It does seem like Yellow would be affected by OBAs.

All your screened colours are affected by OBAs- more so in tones from 1%-50% I.e. the pastels - less so the darker tones.

 

[gordo]

Hi Gordon,

I don't see how normal CMY inks can block all of the effects of OBAs. Since all these ink do not block all the transmitted and reflected light in the visible spectrum, I suspect that they also can not block all the UV light. Certainly they could not block all the generated blue light from the OBAs back out to the eye. So UV light would only have to pass only once through the ink film in order to generate the blue light. Passing once through the ink film results in quite a bit more light getting to the print surface than what is normally measured when reflected back to the eye because the light is filtered on both passes.

If I remember right, in some of your past samples of print in only visible UV light, one could still see the image where the ink was placed on the print. If ink would block all the UV light, then those areas would be black.

Maybe it is more correct to say that the ink would block some of the effects. Can you comment.

For all practical purposes the effect of OBAs is blocked by the inks in the solids.

 

[JohnTheMathGuy]

For all practical purposes the effect of OBAs is blocked by the inks in the solids.

I have looked at actual data, comparing M2 and M1 measurements. From this, I can say that a solid black or yellow effectively blocks all OBAs. I suspect that black just blocks everything and that yellow largely blocks the emitted fluorescence.

Solid cyan and solid magenta inks block about half of the OBAs. This is obviously dependent on the pigments that are used, since the inks are not usually characterized in the UV.

 

[Deleted member 16349]

I have looked at actual data, comparing M2 and M1 measurements. From this, I can say that a solid black or yellow effectively blocks all OBAs. I suspect that black just blocks everything and that yellow largely blocks the emitted fluorescence.

Solid cyan and solid magenta inks block about half of the OBAs. This is obviously dependent on the pigments that are used, since the inks are not usually characterized in the UV.

Thanks John. Based on the shapes of the cmyk reflective curves, I would expect exactly what you have stated, assuming that the curves did not change that much as they go into the UV range. Glad you had some measured values to confirm that.

 

[Vernon Roberts]

I have looked at actual data, comparing M2 and M1 measurements. From this, I can say that a solid black or yellow effectively blocks all OBAs. I suspect that black just blocks everything and that yellow largely blocks the emitted fluorescence.

Solid cyan and solid magenta inks block about half of the OBAs. This is obviously dependent on the pigments that are used, since the inks are not usually characterized in the UV.

Nice, so I should be able to just import the standard as is into the Image Control. I don't have a modern handheld to check differences between wet, dry, M0, M2. I have an i1iSis scanner, the first version. I'm able to switch between M0 and M2 on it and scan targets. I can compare some readings for the solids by eye dropping manually in Color Toolbox. It's all very inconvenient without a handheld.