Converting CMYK ISO Coated to Grayscale - Offset

[SilvaJr]

Dear forum readers:

We are printing in a print shop under ISO 12647. We had been using ISO Coated, PSO Uncoated and MFC icc profiles in our envinronment (FOGRA 39,47 and 41).

We need extra information about how to handle the following scenario: we need to convert PDFs from CMYK to a grayscale icc Profile.

Which Gray ICC profile do you recommend us to apply in such conversion? Is there any well recognized gray icc profile in the market? We are afraid to apply a standard generic gray and pictures starts to become washed.

Thanks in advance for any help in this matter.

Best Regards,

[mazengh]

I have attached the ICC profile that came with our rip, it's a CMYK profile that has a black channel only, and it's suitable from convert from ISO CMYK to just K. I hope this helps.

[Thierry]

I don't know if this will help you (as far as I know, it only works with Photoshop): You may use whatever profile you want just by choosing Load Grey level in the Grey level of the Edition>Colors of Photoshop and then choosing a suitable profile. This way, Photoshop will use the black curve of this profile (ISOCoated v2, PSO uncoated, etc.) and your image will be translated to gray level using the dot gain specified in this profile. Sorry, the screen captures are from a french version of Photoshop.

Another solution: Basiccolor released a grey profile based on ISO Coated v2 (named ISOcoated_v2_grey1c_bas.ICC). You can download it at the following address:
http://www.colormanagement.org/downl...ffset_2009.zip

[michaelejahn]

There are several approaches to convert PDF files containing CMYK, CMYK plus Spot or RGB type, images or objects. PDF files support many other color spaces that need to be managed - it is not that uncommon for a CMYK image that has less that 256 unique colors to be converted to index color - an example might be a color TIFF file of a logo.

I will assume that the solution suggested by Thierry might not work for you, as this seems to assume that you would convert entire PDF documents into TIFF files - unless converting to - lets say - 600 ppi greyscale is acceptable to you - it might just be that is fine - but using Photoshop as a RIP may create other issues.

Compose has many customers who choose to do this conversion in the RIP we sell - and while it is common and somewhat typically to do this sort of thing in our RIP, but I will be the first to admit this might not be the best place to do it.

I know that Enfocus, Callas and others convert to greyscale PDFs - I also know some simply use Adobe Acrobat "fix-up" profiles to do this sort of thing - we sell ALWAN CMYK Optimizer which can do this as well.

I have not tested the profile that mazengh posted - that might just do the trick, I do not know.

Besides the issue of what gets converted to what - CMYK images can convert into greyscale, but most photographers NEVER use a simple mode change in Photoshop, using the the conversion tool in Photoshop found under the Image menu > Adjustments > Black & White

example - what Black tint does 100% yellow type convert to ? What happens when you have 85m85y over 100c100y ? (hint, they convert to the same grey)

[rich apollo]

As Michael alluded, there's really no "one-size-fits-all" method. Much will depend on the incoming colorspace, and much will depend on the final print conditionsl. Now, Thierry's method will also allow you to export a grayscale profile from Photoshop that can be used as your destination colorspace. So, for your purposes you could convert from whichever FOGRA flavor to a grayscale profile built from the black channel of the same FOGRA dataset. That might give you a workflow that is defensible against clients that are unhappy with the results

[pkleinheider]

Another thing you may want to consider: doing an ICC conversion of text from DeviceCMYK 0/0/0/100 to Grayscale does not result in 0% Gray (aka black). An ICC based conversion is more likely to result in 5% Gray (depending on the combination source/destination ICC profile).
If you have the need to keep black line art objects (as well as tints of black), such elements have to be mapped to DeviceGray rather than converted via ICC profiles.
Most of the named apps (performing conversion in PDF file format) are capable of doing so.

Cheers,
Peter Kleinheider