Single color black text (CMYK K100) for printing

Bloom
1

Our printer has given us the feedback that our black text is being printed as a four-color overlay (CMYK black). They insist that that it should be single color black CMYK 0,0,0,100 (K100). The color of our black text according to the color palette is #000000 or rgb(0,0,0) which, according to color converter, is K100.

We tried giving them PDFs both after conversion to CMYK (Bloom Enterprise) and without CMYK conversion … same complaint by the printer. Anyone know how to get text in “single color black K100” for printing ?

I don’t think that the font is related to the color, but in case there is some connection, we are using Andika.

2

If you have Acrobat Pro, you can do this with the Preflight tool:

  1. select the Preflight tool
  2. from the “Essentials” list, look in the “Profiles” tab
  3. Under “Digital printing and online publishing”, select “Digital printing (B/W)”
  4. Click “Analyze and fix”

(If you don’t have Acrobat Pro, it’s possible to use Ghostscript instead: see here for some possible approaches.)

3

Hi Fraser … Thanks kindly for your reply.

We don’t have Acrobat Pro … Ghostscript is an option for us but before going further down one or the other path, perhaps you might be able to answer a question or two to help me better understand the problem and solution.

First, simply, our books have many color images … we only want the text in 0,0,0,100 black, we don’t want the images converted to greyscale. Will Adobe Preflight change just the font ?

I wonder about my question … why, if the font is RGB 0,0,0 it is not converted to CMYK 0,0,0,100. I have read more than I ever wanted to know about “Rich Black”, apparently 60,40,40,100, which some say is better for printing than 0,0,0,100 and other say the two are completely indistinguable to the human eye. What does Bloom do when it converts to CMYK ? Is it possible that it is 60,40,40,100 instead of 0,0,0,100 and that it actually won’t make any difference when printed and I should just tell my printer to go ahead and print what is there ?

Preflight tools are really expensive - you don’t know of any free or cheap ones by any chance ? (Aside from Ghostscript, which is a minor inconvenience to get it running on my computer and the fact that I haven’t used it for … I think some 20 years and will need to get up the learning curve again for little long term return (I hope that doesn’t sound lazy ! … just so many hours in a day)) Is there anyway I can tell myself what color coding is used in the PDF for the font ? I thought that the Bloom development team should be able to tell me since you can look at your CMYK conversion code.

4

Just an additional note … so I think a good question is what does Bloom do when converting RGB (0,0,0) to CMYK ? After more reading, I see that Adobe Photoshop will convert it to C75 M68 Y67 K90, which some say doesn’t print well, some recommend C60 M40 Y40 K100 and my printer wants C0 M0 Y0 K100. In any case, I’m sure the Bloom development team can tell me what you currently do. Is this modifiable during the conversion rather than trying to correct it after creation of the PDF ?

5

Michael IIRC Bloom uses ghostscript internaly so if gs can do what you need, we can build this in.

–John

6

Hi Michael,

John is correct, Bloom uses Ghostscript internally to convert RGB to CMYK (you can see the current code here.) It looks as if Ghostscript >= 9.54 can be used to change the color space of only the text of a PDF document (see here), but I’ve never tried it. @JohnHatton Thanks for offering to put this into the roadmap (assuming it’s really possible, of course).

we only want the text in 0,0,0,100 black, we don’t want the images converted to greyscale. Will Adobe Preflight change just the font ?

Yes, Acrobat Pro can do this – but you’re right, Adobe’s tools are awfully expensive. I don’t know of free or cheap ones (apart from Ghostscript) that will do the same.

Is there anyway I can tell myself what color coding is used in the PDF for the font?

Well, Acrobat Pro will (sigh) – aside from that I’m afraid I don’t know.

– Fraser

7

I took a look and identified the offending code … it is here

            case OutputType.Printshop:
                // This reduces images to 300dpi, converting the color to CMYK.
                bldr.Append(" -dPDFSETTINGS=/prepress");
                bldr.Append(" -sColorConversionStrategy=CMYK");
                bldr.Append(" -sColorConversionStrategyForImages=CMYK");
                bldr.Append(" -sProcessColorModel=DeviceCMYK");
                bldr.Append(" -dOverrideICC=true");
                var rgbProfile = FileLocationUtilities.GetFileDistributedWithApplication(
                    "ColorProfiles/RGB/AdobeRGB1998.icc"
                );
                var cmykProfile = FileLocationUtilities.GetFileDistributedWithApplication(
                    "ColorProfiles/CMYK/USWebCoatedSWOP.icc"
                );
                bldr.AppendFormat(" -sDefaultRGBProfile=\"{0}\"", rgbProfile);
                bldr.AppendFormat(" -sDefaultCMYKProfile=\"{0}\"", cmykProfile);
                bldr.AppendFormat(" -sOutputICCProfile=\"{0}\"", cmykProfile);
                break;
        }

I think it is “ColorProfiles/CMYK/USWebCoatedSWOP.icc” which determines the conversion from RGB to CMYK … it’s a CODEC and not exactly easy to figure out without some study. But USWebCoatedSWOP is the profile used by Adobe Photoshop (actually, USWebCoatedSWOPv2.icc) which does convert RBG 0,0,0 to C75 M68 Y67 K90 - at least according to many sources.

Apparently, there are a number of standard profiles used in different places in the world and it may be that by specifying a different profile file we can get the conversion we want. I asked the printer (they are in China) if they can tell me what profile they use. The ability to specify what profile to use could be a feature in Bloom for CMYK conversions … I think it could be useful in different parts of the world. However, in the short term, I think we probably are going to have to run our own conversion, whether with whatever profile our printer uses and Ghostscript, or by plunking down for Adobe Pro.

8

ghostscript: convert PDF into CMYK preserving pure Black for text - Stack Overflow talks about this very issue. I haven’t been able to get the suggestion to work, so you may need a newer version of ghostscript than we ship with Bloom, as indicated earlier. (We still provide ghostscript version 9.21 from 2017.)

9

Sorry to possibly overload this discussion (and also to reply to my own reply) but this comment I ran across gives an idea about color profiles and the different needs for “web” and offset printing. I think my conclusion is that CMYK conversion in Bloom is a nice feature, but it may not always be useful unless one can specify the color profile. I know that there are a million things on the list for Bloom to add so I’m not sure this is going to be high priority - if you go to the printshop it may be that it is necessary to invest in some tools. We have printed books straight from Bloom, in RGB and with low-resolution images … and they looked great, a child enjoying the book would not notice any difference between these books and high fidelity digital printing.

Anyway, here is the expert on color profiles:

“I post this because I’m a prepress operator and a G7 Color Expert. Most file submissions to printing companies do not use the correct Destination Profile, they use the default settings in whatever application used. US WebCoated SWOPV2 is for web printing and the maximum ink limit due to web paper is 300% in contrast to an actual offset printing ICC profile like GRACoLCoated2013.icc or CRPC-6 for Coated papers (max ink limit 320%) and GRACoLUncoated2013.icc or CRPC-3 for Uncoated papers (max ink limit 280%).”

Other print and color experts grouse about the unwashed masses thinking that anything CMYK should do the job, when it doesn’t. I was warned … a friend with access to “Preflight” tools checked our books over a year ago and said they would never pass muster with any printer and that we would have to rework them. After getting acceptable results with our print run with not very demanding printers locally (but very expensive), we thought we could slip by …

10

Bloom doesn’t allow adding color profiles, but it probably wouldn’t be hard to do so by adding files to the folder we store the current one in, and fixing Bloom to build the list of profiles from the files found there instead of assuming only one file. That won’t happen immediately.

11

Hi @Michael_Leventhal.
We’re looking at enhancing this now for Bloom 6.1 Beta.