Best way to convert PDFs to grayscale?

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magnussandstrom
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Best way to convert PDFs to grayscale?

Post by magnussandstrom »

Hi, I'm building a flow that converts any PDF (containing more 1 separation) to gray. The input PDF's will vary and contains everything from CMYK images, RGB images to Spot line art and so on. I would like the output file to be as aesthetically pleasing as possible with contrasty b/w images. If the there is any grayscale images in the input PDF I would like to keep those images 'as is'. The output PDF will be printed accordingly to PSO Coated v3 black curve (F51).

Tools at hand is: Switch, Pitstop Server 2022 and Callas pdfToolbox server 11

When I try to do this with pitstop actions all the converted images gets very low contrast (no matter my choice of color settings or gray profile in the Pitstop Configurator color settings). I've tried to add a contrast curve in Pitstop, but that will also apply on images that was already provided as grayscale and I doesn't want that.

When I use Callas pdfToolbox ConvertColors (Source Prepress.cfg Destination BlackAndWhite.cfg images looks really nice but sometimes vector objects (Like 100% Cyan) gets converted to 100% White(!). It's too unreliable.

I guessing many of you also converts PDF's to grayscale, what is your approach? Any suggestion how I can get better results?
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JimmyHartington
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Re: Best way to convert PDFs to grayscale?

Post by JimmyHartington »

Hi Magnus

I do not know if it helps, but I use this action list: https://d.pr/f/VbqtIE

And these settings in the Pitstop Configurator:
Image

But I have not that big a need for converting to greyscale, so it is not that used.
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magnussandstrom
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Re: Best way to convert PDFs to grayscale?

Post by magnussandstrom »

Thanks Jimmy,

I got a suggestion from Jan Suhr to use the Fixup Convert to Grayscale instead of the ConvertColors function in callasPDFToolbox and it seems to do the trick (so far).
jslater
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Re: Best way to convert PDFs to grayscale?

Post by jslater »

I don't know if you've tried this, but we have pretty good results from overriding color management and remapping to gray in PitStop. It would look something like this:

Save current color management settings
Override color management settings (set to No)
Select All
Remap color (we define each color space to remap to gray)
Restore previous color management settings
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