Identify CMYK Colors

Lawrence

The eps file would have been converted into a .pdf file in Pages possibly using ColorSync filters and whatever they may have been set to.

It is also possible that the color picker in Pages is simply giving you the screen values.

Why are you opening the .eps in Photoshop? I would assume that it is probably a vector graphic and should have been opened and resaved from Illustrator with the correct values and color management set.

Are you intending to take this brochure to commercial print? If so how were you intending to deliver it to the printer?

Peter

On the answer:

Per the ICC Specification, Encapsulated PostScript can contain either tagged ICC file format CIE references or tagged PostScript level 2 CIE references (CSA Color Space Arrays).

Adobe Photoshop is able to tagged both colour management formats to the same objects at the same time in Encapsulated PostScript which was not a good idea to begin with.

A PostScript level 2 or 3 processor will read the PostScript format CIE references. For the ICC CIE format references to be read, an ICC frontend is required.

On the question:

RGB, CMY and CMYK are no more than data models for colourants. A CMYK combination does not define a colour except in one and only one printing condition.

To form the same colour in any other printing condition, even on the same printer or press, it is necessary to know the CIE value of the colour and calculate the colourant combinations from that.

This is what an ICC PRTR Printer profile does, that is, for any given CIEL a*b colour it calculates the corresponding colourants to create that specified colour on the colour device.

In Apple iWork applications, for instance, one creates an object with the application drawing tools and one then chooses its colourant format and its ICC colour space in the Apple ColourPicker.

The rule is to unify the area separation, that is, avoid specifying one colour in one ICC PRTR Printer profile in one part of the page and specifying another colour in another ICC PRTR Printer profile in another part of the page.

Better still, avoid specifying colours in ICC PRTR Printer profiles. Specify colours in a normalised/idealised ICC MNTR Monitor profile such as AdobeRGB 1998, ECI-RGB or other such working space of satisfactory size and shape.

The ICC colour management system will convert the RGB colourants to CIE colours and then convert the CIE colours to CMYK colourants for the intended printing condition, unifying the area separations automatically in the process.

/hh

I have a logo in an EPS file, and I used a color picker in Photoshop CS5 to check the colors' CMYK values, but when I use a color picker to match them in Pages, it gives me different CMYK values

What would be the best way (workflow) to get a brochure designed in Pages over to a print company and ensure that the colors of my graphics (created in Pages) matches the true color of the logo? The printer I'm using requested CMYK colors for my logo when I went to print business cards (which I did in Photoshop).

Right, well ...

Adobe Photoshop 6 and higher will always colour manage, including when colour management is set to off. If colour management is set to off, the default working space will be used to specify the colours to be formed by the colourants, but the default working space will not be embedded when the data is saved disk.

The colours are device independent if and only if the data is saved to disk with the ICC profile for the data (whether it be the application default working space for the data or the working space set up for the window session). In other words, the data will be colour managed inside and not colour managed outside Adobe Photoshop 6 and higher.

If the Adobe Photoshop image window says 'Untagged CMYK' in the lower left, there is no embedded ICC profile. Instead, the default ICC profile for the data format, in this case CMYK, is assigned as source to get to the CIE colour connection space, and the ICC monitor profile (from the ColorSync registry) is assigned as destination.

However, because there is no embedded ICC profile, every installation of Adobe Photoshop will show the same data in different colours, even if the systems have correctly measured and correctly installed ICC monitor profiles, because the systems may make different assumptions about what source ICC profile should be assigned to the data.

Four component data for an offset lithographic drawing condition cannot be directly imaged in a display drawing condition for three component data. The data has to be converted one way or another, and if colour management is set to off there is no other way than to make assumptions and assign ICC profiles accordingly.

So far, so good.

If you want to specify colours in CMYK values in Apple Pages, and if you want the CMYK values to specify device independent colours, then you have to extract the ICC profile embedded in your EPS, install that profile into the Apple ColorSync data base, and select that profile when specifying colours in Apple Pages (: Apple Colour Picker).

If so, you will be using a CMYK interface to specifying device independent CIE colours, since every ICC profile defines the conversion of a colourant data space into a standard CIE colour space (CIEL a*b or CIEXYZ). This is unwise, because an ICC PRTR profile with data space CMYK is not particularly linear, that is, equal amounts of colourant will not necessarily define gray.

What you should be doing from the start.

If a printer supplies EPS, which is obsolete; and if a printer specifies in CMYK components whithout specifying the ICC PRTR Printer profile that forms the colours and computes the colourants for the printing condition that is sold as a service, then the printer is probably not competent in the use either of Adobe, or Apple, or Quark or any other ICC-enabled processing.

The printer should be supplying an ICC PRTR Printer profile for the OutputIntent of ISO 15930 PDF/X and you should be installing that in your system software as the CIE colour definition of the lightness and tint of the printing paper and the colour positions in the colour space from shadows to midtones to highlights. Then you should embed that as your OutputIntent.

What Peter will be posting.

Peter will be posting that ISO 15930 PDF/X-3 does not use the transparency imaging model of PDF 1.4 but the opacity imaging model of PDF 1.3 and lower and PostScript 3 and lower. Therefore, mapping of the transparency to opacity must be manually managed. Either in the Apple ColorSync Utility, or by saving out PDF 1.4 and managing the mapping in a third party post-processing application like Enfocus Pitstop or Acrobat Professional.

Hope this helps,
Henrik

Could you explain how I should extract the embedded ICC profile from an EPS?

Provided the EPS contains one and only one object (in this case, one colour bitmap), there may either be one ICC characterisation, one PostScript CSA characterisation, or both (embedded as %%PS comments).

As explained, provided the EPS contains one and only one object that references one CIE characterisation, Adobe Photoshop 6 and higher will show what characterisation it is by name in the lower left of the document window.

If you want to do what the printer wants you to do, then you either have to extract an ICC profile from the EPS or tell the printer to e-mail you the ICC profile embedded by the print shop into the EPS. If I were you, I would do the latter.

Apple ColorSync comes with AppleScripts that extract profiles from from file formats that support one and only object, TIFF and JPEG, but if memory serves at this time of night, the AppleScripts don't support extraction from EPS and PDF.

ICC PRTR Printer profiles for ISO 12647 reference printing conditions are available at www.eci.org. The characterisation data for same is available at www.color.org which is the web site of the International Colour Consortium.

/hh