Spot Color Delta E

[Deleted member 16349]

If you want to formulate a Pantone color so that it appears the same on different colored substrates then you are in the realm of experimentation and you will need to be sure that is what your customer actually wants as well as whether it is technically possible (as it may not be).

best, gordon p

Where I work, we print with the Dry Offset process and all the inks are spot colours and they are mixed from blending inks to obtain Pantone matches or at least as close as one can get. We print on plastics and there is some small colour variation even in the the different white plastics used. But in general, mixing inks to match the Pantone guide is common practice for Dry Offset.

There is an attempt to print ink to match Pantone colours on coloured plastic but as you said, it is not possible to do for all the Pantone colours.

 

[michaelejahn]

Pantone does provide LAB to RIP partners

Pantone does provide LAB to RIP partners

AFAIK (working with Pantone techies), the CIEL*a*b* values (in RIPs and instruments) associated with Pantone colors are a courtesy to enable better CMYK simulations or to determine the closest PMS color to an unknown sample.

indeed, you are correct (as usual!) - just got a quick note from my buddy and co-worker from years back - Andy Hatkoff -- Vice President- OEM and Technology Licensing, who writes;

The RIP vendors that have license agreement with [Pantone] get L*a*b* data for PMS coated, uncoated and matte and Goe coated and uncoated in the form of an Excel file which is then incorporated into their respective solutions. Some vendors request our CMYK values (but this is rare and often supplements the L*a*b* data).

I guess my brain has become fried. I am working on a PDF Healthcare project and not getting much sleep !

Michael Jahn's blog

 

[Greg Imhoff]

Pantone spectral values in the pressroom

Pantone spectral values in the pressroom

If the question is "how many Pantone books match" each other? Pantone books are as I understand printed offset and in very controlled situations. These books have not historically matched each other well as we know offset is by its nature, relative to the target not identical. This may help explain why as I've been informed the original Pantone color reference samples were "wrapped in foil and stored in a refrigerator." Still offset has its issues yet is also with many clear printing advantages.

A DE (Delta E) depending upon any applied math model can vary on the same and on different colors too. For example specing a CIE Delta E of -1 for Grays may be more readily seen yet - specing a CIE DE of -5 for a Process Yellow would in most press rooms, be more difficult to see. Some CIE models are "weighted" better than others and controlled lighting, is another key.

Instrument accuracy and repeatability are the printers best tools and keys to color match. I do know more than just a few "in plant ink" shops using spectros to formulate and proof from - if required by management. Differences are related not solely to CIE math models but also to other variables as well ie: human ergonomics.

Consistency and accuracy are as always, most important to printing profitably.
Sincerely,
Greg Imhoff
(708) 557 - 2021

I don't believe there is a delta E tolerance for PMS colors. Even the latest Pantone GOE library does not mention tolerances or CIEL*a*b* values.
Typically swatches/draw downs are acompanied with a "Hi-Lo" density reference.

BTW a Delta E of 5 can be a good match as the visual perception of difference depends on the hue you're measuring and how the Delta is being calculated.

best, gordon p

my print blog here: Quality In Print

 

[gordo]

Pantone books are as I understand printed offset and in very controlled situations.

A KBA dry offset press - no water - I believe.

best, gordon p

my print blog here: Quality In Print current topic: The Wayback View - A visit to Sun Chemical Ink 1951 (video post)

 

[Greg Imhoff]

Right Gordo I think printing from "Split Fountains" as well.
The new press (ttbomk) updated a ~ 25 old machine no doubt vastly helping color match missions.

Greg Imhoff
(708) 557 - 2021

 

[BacekJon]

We are pharmaceutical packaging plant and we use now about 450 colors from Pantone guide (400 Coated and 50 Uncoated). We have an agreement with ink supplier, who make for us specifications with L*a*b* values and colored sample (it's special tool where this samples are made – I don't know the name of this tool) for each color. Then I send this L*a*b* values to our suppliers (printing houses – we have about ten of them) who are obligated to print each color within dE=8. We use delta E CIE L*a*b* (formulae CIE1976). I have made some test (about 50 different colors along whole spectrum) with formulae dE2000 but I didn't percieve some special benefits of this formulae. We all (our company, ink supplier and printing houses) use same instrument (X-Rite SpectroEye, D65, 45/0, 2°, POL filter).
But … I must admit that we have some problems. Colors are very alive. That means suitable color (within dE=2-3) right after printing process, but unsuitable color after day or two (or maybe a week) when ink penetrates into printing material (especialy Uncoated papers). Some colors (red, dark blue-Reflex Blue and violet colors especialy) have a predisposition to vary with time (sometimes more than dE=12).
So we are trying now to determinate those very problematic colors (less than 10% of all colors). I think that we will determine »higher« dE for those colors or maybe just measure new L*a*b* reference of dry color.
I partialy agree with Gordon (don't believe there is a delta E tolerance for PMS colors. Even the latest Pantone GOE library does not mention tolerances or CIEL*a*b* values.
Typically swatches/draw downs are acompanied with a "Hi-Lo" density reference. BTW a Delta E of 5 can be a good match as the visual perception of difference depends on the hue you're measuring and how the Delta is being calculated.) but we recieve more than 100 packaging materials a day (folding boxes, leaflets, leabels, foils, ….) so we have to have suitable (fast) system for estimating colors.