Converting CMYK Black to Black...

[kdw75]

Some of the files we receive in PDF format consist of a solid black background with some artwork on it. The file is apparently set in photoshop and then saved as a PDF. Against all our recommendations their designer refuses to save anything as vector data. It is all rasterized then saved as the PDF.

The black though isn't pure black. It is around 88% K with random percentages of CMY. This comes out rather brown and muddy rather than pure black.

Does this sound like the designer is starting in RGB and then converting to CMYK? More importantly is there any method of converting the black into pure 100% black or does the fact that it is a raster image make that impossible?

 

[Greg_Firestone]

Hi kdw75,

The "out of the box" black in Photoshop is a rich black build of 75C, 68K, 67Y, 90K. If you're getting a different set of values, they might be using an RGB.

If content is a raster PDF, you're out of luck to do a quick fix unless you want to start masking everything off and manually fixing in photoshop.

I have seen some other strange behavior with Photoshop PDFs. Not exactly sure how it happens. As far as I can tell, the designer had CMYK black text. When the PDF was made, the text essentially became a mask and the fill was actually a raster image behind it. The text has no fill. The way to fix this is to manually grab the image and convert it to K only. Works for those files, but might not for you depending on the exact problem you're having.

Greg

 

[kdw75]

That is what I was afraid of. I have been able to go in and manually fix it up somewhat in photoshop but wanted to make sure there wasn't an easier way. The designer just seems to want to keep doing what she is doing. The client seems to just go along with the designer even though they agree that the quality is suffering. I have tried to talk her into providing files that aren't rasterized but so far it has fallen on deaf ears.

 

[DCurry]

Here's a way to quickly convert 4-color Photoshop blacks to K only. Beware - the downside is it will change the builds of all the colors, so use with caution. It works great.

You need to reseparate using Maximum Black Generation. Go to Color Settings and in the Working Spaces CMYK dropdown choose Custom CMYK, set Separation Type to GCR, Black Generation to Maximum and Black Ink Limit to 100%, UCA Amount 0%. Be sure to name it something that makes sense, like "Max GCR" do you can easily find it later (you'll see in a minute) Click OK.

Now you are back at the Color Settings dialog, but don't click OK here just yet. Go back to the same Working Space CMYK dropdown and choose Save CMYK and save then setting - it should default to the name you already gave it and it should also default to saving in the proper Profiles folder. Save it, then get out of the Color Settings window by hitting Cancel.

At this point, since you cancelled out of the Color Settings dialog, you haven't altered your normal CMYK settings at all. But you did create a Maximum Black Generation profile that you can use on the fly anytime you need to do this, without having to go back into the Color Settings at all:

To use it, open the image you want to fix and go to Edit>Convert to Profile and pick your MaxGCR profile. Upon completion, all your rich black will not be K only. There may be remnants of CMY, but only a couple percent here and there which is fairly easy to clean up with a curve, or just leave it alone. If the black isn't quite solid (like say 97% or something like that), a curve on the black channel can fix that as well (input 97, output 100).

Sometimes it is helpful to run a Trap filter (Image>Trap) of a pixel or two to help with registration on press, because your RIP's trapping probably won't trap inside images.

Hope I explained that clearly enough to follow!

 

[kdw75]

Thank you very much. I will give that a shot and see if that works for me.

 

[kdw75]

Here's a way to quickly convert 4-color Photoshop blacks to K only. Beware - the downside is it will change the builds of all the colors, so use with caution. It works great.

You need to reseparate using Maximum Black Generation. Go to Color Settings and in the Working Spaces CMYK dropdown choose Custom CMYK, set Separation Type to GCR, Black Generation to Maximum and Black Ink Limit to 100%, UCA Amount 0%. Be sure to name it something that makes sense, like "Max GCR" do you can easily find it later (you'll see in a minute) Click OK.

Now you are back at the Color Settings dialog, but don't click OK here just yet. Go back to the same Working Space CMYK dropdown and choose Save CMYK and save then setting - it should default to the name you already gave it and it should also default to saving in the proper Profiles folder. Save it, then get out of the Color Settings window by hitting Cancel.

At this point, since you cancelled out of the Color Settings dialog, you haven't altered your normal CMYK settings at all. But you did create a Maximum Black Generation profile that you can use on the fly anytime you need to do this, without having to go back into the Color Settings at all:

To use it, open the image you want to fix and go to Edit>Convert to Profile and pick your MaxGCR profile. Upon completion, all your rich black will not be K only. There may be remnants of CMY, but only a couple percent here and there which is fairly easy to clean up with a curve, or just leave it alone. If the black isn't quite solid (like say 97% or something like that), a curve on the black channel can fix that as well (input 97, output 100).

Sometimes it is helpful to run a Trap filter (Image>Trap) of a pixel or two to help with registration on press, because your RIP's trapping probably won't trap inside images.

Hope I explained that clearly enough to follow!

This worked perfectly. I can't tell you how much this will help me as this is a monthly account. I am shocked how well it worked.

 

[Stephen Marsh]

kdw75, as your image is mostly K with random small % of CMY, do you really need to do a profile conversion to Max GCR (which is basically giving you a similar result)? Why not just hit the image with a curve to blast our the CMY and darken the K?

I would also look into using a proper ICC profile that produces only K, so no need to use a curve to blast out CMY:

http://printplanet.com/forums/color-management/25021-converting-cmyk-iso-coated-grayscale-offset
http://printplanet.com/forums/attac...ted-grayscale-offset-converttok_isocoated.zip

http://printplanet.com/forums/color...yscale-profile-black-ink-gracol2006_coated1v2
http://printplanet.com/forums/attac...ink-gracol2006_coated1v2-gracol-black.icc.zip


Stephen Marsh

 

[DCurry]

Stephen, my guess is that she doesn't want to convert to Grayscale - there are color elements that need to remain so. My method retains colored areas while forcing areas that appear black to be on the black channel only.

 

[Stephen Marsh]

Cheers Dan, you may be right in that guess.

Perhaps I need another coffee, however it sounds that a profile transform is not need and curves could perhaps do it all.

I have used the legacy Custom CMYK tables many times when I don't have a proper profile that suits my needs, however my preference is to use a good profile.


Stephen Marsh

 

[kdw75]

The mailers tend to have a black background that floods the sheet. This is made up of the black that is 89% K with amounts of CMY. Then on top of that is complex artwork using process color images. On the press the only real issue is that the black doesn't look quite as rich as it should, though most would not even notice. On the pieces that need to be run digitally I don't want to waste the CMY toner on a black background when 100% K would work just great.

 

[Stephen Marsh]

Thanks kdw75 - now I understand your concerns and issues better, cheers!

Stephen Marsh

 

[mattbeals]

So one of the little known features of callas pdfToolbox is that you can select a specific cmyk build (+/- a few percent if you like ) and then define a new cmyk value. So if you know what the source build is and what the destination value is then pdfToolbox can make this change to vector object and/or raster images.

 

[kdw75]

So one of the little known features of callas pdfToolbox is that you can select a specific cmyk build (+/- a few percent if you like ) and then define a new cmyk value. So if you know what the source build is and what the destination value is then pdfToolbox can make this change to vector object and/or raster images.

That sounds very useful.

 

[claude72]

The "out of the box" black in Photoshop is a rich black build of 75C, 68K, 67Y, 90K.

The "out of the box" black in Photoshop depend of the profile used... by default, Photoshop is set with different profiles depending of the country where it's sold and depending of the versions: in USA it's a SWOP-something, but in europe for some versions of the CS it's a Fogra 27, giving a rich black C86 M85 Y79 B100.

If you're getting a different set of values, they might be using an RGB.

CMJN or RVB doesn't matter: if the picture is in CMJN mode, the rich black is created using the workspace profile...
... and if the picture is in RVB converted to CMJN in the same Photoshop, the conversion will also use the profile of the workspace, meaning that the same profile is use in both cases and will give the same rich black.

I have seen some other strange behavior with Photoshop PDFs. Not exactly sure how it happens. As far as I can tell, the designer had CMYK black text. When the PDF was made, the text essentially became a mask and the fill was actually a raster image behind it. The text has no fill.

It's the normal way that Photoshop uses to include the vector text of its "vector" text layers in a PDF...

The way to fix this is to manually grab the image and convert it to K only. Works for those files, but might not for you depending on the exact problem you're having.

When I had that kind of butcher job, I used to make two separate picture from the original PSD (or Photoshop-PDF) file:
- with Photoshop I made a TIFF picture of the background from the PSD after removing all the text,
- then I rfemoved all the background, leaving only the text and exported an EPS or PDF. Then with Illustrator (which is not a PDF editor, but it doesn't matter as I DO NOT edit a PDF, but I recreate another file from a PDF), I made an EPS picture containing all the text in outlined mode. Using Illustrator allowed me to clean the text, remove all the masks, remove all the colorising picture and other unuseful stuff added by Photoshop, and then, by using the Illustrator tools, colorised the text in the wanted color (with or without rich black) AND handle manually the knock-out and overprinting of the text as I need.
Then, I re-assemble this 2 pictures in InDesign, the text picture beeing on top of the background picture, exactly superimposed. It allows to keep the text in vector mode, get correct knock-out/overprint (and add vector logos), and makes a perfect printed job from a crappy Photoshop layout.

Of course, this method works only if you can get a Photoshop file in PSD or PDF with all the layer, mainly the text layers!!!