Best practice for RGB and grayscale images for digital and print?

I suggest first applying a Black & White adjustment in Photoshop. This will work for both the tinted version of the photo and hte grayscale version.

One problem from converting colour images to grayscale is that colours with high contrasts, like red and green, sometimes convert to simlar shades of gray. You end up losing detail and contrast. The Black & White adjustment will let you adjust how different colours convert to grayscale, allowing you to enhance contrast that would otherwise be lost.

In the same adjustment panel you can apply a tint, which works like the colour overlay you aplied in InDesign.

You can create as action to add the adjustment and set the colours or load a saved preset. Run it as a batch and you can convert severl photos at once. You can even apply multiple versions of the effect (one for the grayscale only photo, one for the tinted version). When you place the images in InDesign you can change the object layer options, switching which version of the adjustment is applied. You also get the benefit of keeping the original colour image in the file.

When you are ready to make the print version you will need to convert the images to grayscale, otherwise they will be RGB images. You can use a batch action for this, too. I suggest saving the grayscale versions in a separate folder and with different names (perhaps appending _GS).

All in all... as much as you might find the color-overlay effect easy to apply and pleasing for at least one use, it might be causing more actual output issues/problems than it's worth. Maybe backing up to a more conventional image placement and color management would solve a lot of issues for both destinations...

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Hi @23121922udmu , can you share an example of the Affinity grayscale? Which version of InDesign are you using?

When Overprint Preview is turned on, InDesign previews placed grayscale values as they are expected to print on the CMYK black plate, so the InDesign document’s assigned CMYK profile has some affect on the preview of the gray values, without changing the actual output values. Some of the contrast loss could be happening with the way Affinity handles the conversion.

Also, what is your document’s Transparency Blend Space set to? The blend space will have a significant affect on the appearance of an Overlay blend.

What if the overlay color was a spot color and when you go to export to PDF and hit the Print dialog box, and then go to Output and then click on Ink Manager, you could simply turn off the spot color ink. It would then ignore that color. Possibly this would give your grayscale images no color overlay, and maybe they will look acceptable to you? (You might try it, anyway.)

Since none of the usual suspects has jumped in, I'll add that the first solution I would look at is optimizing the images for print, then carefully adjusting the PDF export options as to resolution and color conversion. That might let you get optimal results for both purposes without getting too tricky with the document structure.

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If you can't completely resolve the image/graphic issue for both purposes — and I think you can, but there's better advice on that than mine — you can use conditional text to swap two sets of images. I do that for dual-format print/EPUB editions.

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