Convert to Grayscale preflight turns photos very dark

Forum|Forum|29 days ago
March 6, 2026
3 replies
101 views

We have certain items with grayscale photos that use CMYK ink that we need to convert to black ink only. However when I use Convert to Grayscale or Digital Printing (B/W) to achieve this, the photos become extremely dark, unless I turn on Output Preview, at which point they appear brighter. The dark appearance happens whether I’m viewing them in Acrobat or a web browser. Why is this happening, and how can I prevent it? It has caused confusion when proofing to clients.

Using Print Production → Convert Colors → Gray Gamma 1.8/2.2 gives slightly better results for the photos but turns all of the text a faded gray color.

Examples shown below:

Converted to grayscale using preflight, regular viewing in Acrobat/web browser

D

defaulta6qeln3tquadAuthor

Known Participant

Quick update: I tried using Convert Colors, setting the profile to Gray Gamma 2.2 with Perceptual rendering intent and checking Preserve Black and that seemed to give brighter images while keeping the text black. However, turning on Output Preview still makes the images appear even brighter. I’d like to find a way to make everything homogenized so that I’m not left guessing how the print is going to look.

Dave Creamer of IDEAS

Community Expert

Turn on Overprint Preview in Acrobat and see what happens.

David Creamer: Community Expert (ACI and ACE 1995-2023)

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defaulta6qeln3tquadAuthor

Known Participant

That works for InDesign, but it still exports to the darker preview. Is there a way to make that the default appearance?

Dave Creamer of IDEAS

Community Expert

What did it look like in Acrobat with the Acrobat Overprint Preview on?

David Creamer: Community Expert (ACI and ACE 1995-2023)

Dave Creamer of IDEAS

Community Expert

Try adjusting the color photo with the Black and White adjustment filter before converting to grayscale. Also check your grayscale conversion settings.

David Creamer: Community Expert (ACI and ACE 1995-2023)

D

defaulta6qeln3tquadAuthor

Known Participant

Do you mean to adjust it using Photoshop? Some of these can be long multi-page booklets where we don’t have the source files, is the best solution really to go in and edit them one by one?

Luke Jennings3

Community Expert

Sorry for the delayed response.
Dave was suggesting you set your Acrobat page display preference- Use Overprint Preview to “Always” (recommended), which I believe is the default.
The Output Preview tool will give you the best on screen proof of how your pdf will print, select the simulation profile for dot gain that is closest to your print method. I find converting to gray 1.8 to be an acceptable compromise when converting an RGB or CMYK pdf to black only. Use an Acrobat preflight fixup to change a specific color to a darker color (or black) before converting the entire pdf to black only, to avoid faded text.
You can adjust the brightness of your black only pdf somewhat by using a preflight fixup to adjust the midtones, First duplicate the existing midtone correction fixup, then you can edit it to remove or add as much as 25%.
Note, you can also convert to black only directly through the export from InDesign.

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