InDesign 18.3 transparency tool is affecting my grayscale photos contrast

Report · Jun 22, 2023

I have just upgraded to version 18.3 and noticed that when I apply a transparency affect to a background color the photos that are grayscale are also is affected and the contrast changes. I cannot use the tool. I have to change my color manually without the tool (select a different color). What is happening?

Report · Jun 22, 2023

When you apply transparency on a page or spread, it can change the Transparency Blending Space:

Read this somewhat technical note for what's going on:

https://www.printingforless.com/Choosing-a-Transparency-Blend-Space.html

Report · Jun 22, 2023

Here's the key paragraph is the note I just posted:

"But as soon as you introduce ANY transparency into the document (for example, using an effect like a drop shadow, or placing an image with a transparent background), InDesign needs to convert everything in the document to EITHER RGB or CMYK. (This is why you may often see a number of colors or grayscale images suddenly change their appearance on the page when you switch the transparency blend space setting)."

Report · Jun 22, 2023

I have just upgraded to version 18.3

Hi @Margaret306622898tpj , Transparency affecting the preview of grayscales is not new to version 18.

InDesign has no Gray color space, so the preview of grayscales depends on the document’s blend space, CMYK profile and Overprint settings. If you turn on Overprint Preview, or incude any transparency on the spread when the blend sapce is set to CMYK, a grayscale previews as it would print on the CMYK black plate—the document’s CMYK profile is used for the Black plate preview. With Overprint turned off, and no transparency on the spread, grayscale object preview as sGray, which is usful for projects headed for a screen destination. If the blend space is set to RGB, grayscale objects will convert to 4-color CMYK on export or output.

More here on how ID handles grayscale objects

https://community.adobe.com/t5/indesign-discussions/greyscale-jpegs-or-psd-images-are-going-much-dar...