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I've recently bought Pantone Uncoated Color Bridge fan guide (I've owned Formula Guide for some time now) — it's great. What surprises me though is the obvious color shift in Color Bridge (UP) colors. I don't think it's due to the limitations of gamut (brightness, saturation), for example certain blues have an obvious purple tint, even though they would be reproducible in CMYK without any problems.

To demonstrate, here is a diagram I quickly mocked up in Illustrator (I believe my color profiles are set up correctly):

Color conversion in Adobe Illustrator

As you can see, both variants (U and UP) are easily convertible to CMYK. I checked the swatch book and the CMYK percentages after conversion (the squares on the right) match up.

Why are those two so different (notice the big hue shift) to begin with though?

  • This is just one case where, in my opinion, Pantone has a mess on their products. I have not made an answer. the truth is I DONT KNOW! In some cases, yes, there is the "out of gamma" reason, in other... it has no sense. – Rafael May 18 '18 at 9:54
  • Pantone actually have very good reasons for this. Keep in mind that 2748 describes the ink, and the "U" describes the context. "Pantone 2748 U" does not exist as an ink, just "Pantone 2748". The same ink goes on the press whether you're running coated or uncoated stock, yet the resulting color often does look very different. Pantone are just trying to simulate this. Process inks do not contain the pure or fluorescent pigments that many solid inks do, so the closest CMYK breakdowns often look very different. It does make sense once you understand what those "U", "C", and "P" contexts are. – 13ruce Mar 12 at 13:07
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The color bridge UP is the CMYK specified by Pantone for this color. The Pantone Solid Uncoated is not meant to be used for CMYK. This swatch is meant only for spot color printing. Converting Pantone Solid to CMYK is the improper way to get a CMYK value for a spot color. To get technical, Pantone uses LAB to define spot colors and CMYK to define bridge colors and thus the visual difference on screen.

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    I understand that. Still what puzzles me is, why would they choose colours that differ tremendously between the UP and U systems when – apparently – the U colours would be easily reproducible using the CMYK gamut. Surely, it's not just a matter of selecting something in an Illustrator dropdown and there must be some sort of legacy or technical complexities that I am not aware of. – Christian Jánský Nov 11 '15 at 23:29
  • I think the differences are inherent due to how Pantone defines their colors. UP (Uncoated Bridge process color) is meant solely for CMYK printing and thus they define this color in CMYK which renders differently on screen from U (uncoated spot color) which are defined by LAB. I think they chose LAB to define U (uncoated spot colors) to give you a VISUAL match to how the spot color will print when the offset printer actually mixes his inks to produce that spot color. One rarely finds spot color that can be matched with a CMYK mix when printed. – Chung Jan 14 '16 at 16:58
  • It is one of thoose things that Pantone does. :0P – Rafael Feb 10 '16 at 18:39
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TBH, there's no simple way to answer this unless you really understand the printing process. I don't know how much or how little you know, but being that you asked the question I will break it down. Here goes.

The Pantone colors you see on your computer only emulate what will actually print once the ink hits the paper. Each PMS color you chose create what's called a color separation in the file, that the Print house later uses to create a screen for their press. Each screen in the print process, allows for one ink to flow through and land on the form, the sheet of paper, fed through the printing press. In 4 color process printing for example, there are 4 separations or 4 colors that make up all the images you see in your finished product: They are called CMYK. Cyan, Magenta, Yellow, Black. In printing with Pantone inks, the technique is the same, it's just the inks that change. If you chose a blue and a yellow, there will be two screens used. If you choose a blue, a yellow, and a red, three screens will be generated. If you mix CMYK and a PMS colors, five, six or seven screens will be generated.... And your print job will be very expensive :)

The important thing to keep in mind is that the printer (the person) can feed ANY inks in their press even after you've released your files. The files you release are only guides that tell them which inks you prefer in your separations.

To make this process easier for the designer, Pantone came together with Adobe among other developers, and created on-screen, RGB versions of each one of their inks to be viewed trough the design programs. The values you see on the screen are again only representations of the finished printed product. To have a more accurate view of what the finished print will look like you need to look at PMS books.

Now that you know that each color represent a screen, or a color separation, I can introduce Paper Quality as another variable to this process. There are a million different paper types out there, but the most common ones are either Coated (glossy-ish) or Uncoated (rougher, matte). Each type of paper reacts different to the inks.

Coated papers will not absorb as much ink and thus leave more color on the surface. They will also reflect more light, so the colors you see in the end look more saturated and deep on these papers.

Uncoated papers absorb more ink into them, and have a rougher surfaces. Thus more of the paper grain is visible and the colors look more muted, and always are bit lighter. Black for example, will look like a charcoal.

Most designers that have been working with paper for a while are aware of this and once they've chosen how they want their finished product to look, use the appropriate PMS library, to avoid misunderstandings when presenting ideas to clients or designing their materials.

Hope this helps, and if I over-explained it is only because I have no knowledge of your experience.

Good luck!

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Pantone matching books are only supposed to last a year, due to natural fading of inks, sun damage and slow degeneration of paper. You say you had the formula guide for some time, so that may just account for the difference right there.

I've dealt with a wide array of inks and papers over 15 years, and I can tell you, it is very hard for Pantone to do a perfect job every time, so there may be some small shifts between books. But they better not make the shifts too big. We depend on them not to.

  • This is not a printed sample. – Rafael Nov 10 '15 at 22:56
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PS. If you know you will be converting your colors to CMYK, you should do this in your color palette. I find it gives the most accurate conversion, however it will NEVER be the same. That's why Pantone is Pantone and people use their inks rather than cmyk.

And then do your conversion.

in your color palette

Check Use standard LAB values for spot colors

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The truth is that CMYK Pantone colour conversion is a mess... I just ran some of my own tests on spot colour Pantone 2748c (coated)

CMYK Breakdowns for 2748c

Pantone Colour Bridge in Adobe Illustrator = C100 M95 Y2 K10

Pantone Solid Coated (using the printed Pantone swatch book - Solid to Process Guide - Euro Coated) = C100 M94 Y0 K22

Pantone Solid Coated (colour translated into CMYK using Adobe Illustrator) = C100 M90 Y33 K22

Surely the first 2 breakdowns should be exactly the same as they are the CMYK breakdowns that have been specified by Pantone themselves.

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