How To Keep Your Black and White PDF Document From Separating Into Four Color

Get the Color Out Before It Goes to Press!

Troubleshooting 4 color separations can be tricky at times in a world full of RGB (3 color separations) images. But what about black and white? If the person sending you a PDF document doesn't understand that you are working with CMYK (four color separations) for printing reasons, they will send you an RGB image that "looked" black and white on their computer screen. Either this situation can cause headaches or, with the troubleshooting steps ahead, it can be a breeze.

  1. Open the PDF document in its native program. If you have the program and correct version of the program that the document was created in -- for example, Illustrator 9 -- that is great. Just open it and change the document to black and white. NOTE: opening items in lower versions of programs than the item was created in can cause headaches. Better to use the correct version or higher. If the originating program is unknown or not available, move on to step 2.
  2. Open the PDF document in Acrobat 4.0 or above. PLEASE NOTE: not Acrobat reader. A great plug-in for your Acrobat is "quite a box of tricks"; in this extension you can change your document from RGB to CMYK or Grayscale. If you don't have this, try printing to file and choosing black and white as the output colors. This will generate a black and white PDF. Or in Acrobat 6 you can also export to EPS and choose grayscale in the EPS dialogue box (under File >Export). This will create a black and white EPS that you can open in Illustrator or Photoshop and should print OK.
  3. Open the PDF document in Photoshop. This will probably be your most universal option. Often times it helps a lot to have your color settings set to 'MaxBlack' before you open the document. (Click on Color settings > Working space > CMYK > Custom CMYK > Separation options > GCR > Black generation > Maximum, and then hit OK). This will essentially tell Photoshop to use as much black as possible when converting the document. After changing the color settings, open the document and convert it to grayscale. This should produce a nice quality grayscale image. Print it out and see.
  4. Using channels in Photoshop. Another way to convert your RGB file to one plate black and white is to use the channels feature in Photoshop. With your image open, choose 'Show channels' under 'Window'. You will see the 4 (or 3 RGB) separate plate representations of your image. Click on each of these and if the grayscale looks good to you. Trash the other channels and covert your image to grayscale. This works best with photos. NOTE: be sure to flatten your layers if any before saving and closing.
  5. Recreate your document. Unfortunately if your item is mostly text, sometimes your only alternative is to go with a fuzzy print-out or recreate the entire document. Sometimes a fresh scan of the document will help, or completely retyping it.

It's not always an easy or fun part of Graphic Design to check the output of your project. If you are still having trouble trying to keep your black and white images from separating on all 4 plates, consider the source. Find out how the document was created and have the person who created it send it to you the RIGHT way (in actual black and white). Chances are you can get your color problem fixed before it becomes a problem!


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