InDesign overprint black by default

Question

We recently printed something and noticed, that some black box over an image were print as overprint, which lead to a not so perfect looking result.

I checked the files and noticed in Acrobat that the box is indeed set to overprint.

I then checked the InDesign file and saw that overprint was not set for any box in the whole design.

After a quick research I found the default option in InDesign that sets every 100% K field to overprint.

I never knew that this option even existed, because it also never made any bigger problems I noticed.

TL:DR
My question now is: What is the best advise for this setting? Should I set every 100% K to overprint or not?

I know the answer might be "it depends", but what is generally speaking the better option and why?

Because this is a InDesign default setting and not a "per document" I assume this shouldn't be switched around all the time. Is there a way to override this setting for a specific object with 100% K, so I don't have to change the default InDesign setting everytime I open a specific file?

Thanks!

Answer 1

I would recommend to keep overprinting of black turned on. You mostly want small black text and thin black lines to overprint. Making black objects knock out is only something you want to do once in a while.

Actually the setting in InDesign is called Overprint [Black] Swatch at 100%. So it does not automatically overprint any occurrence of 100% K, only the swatch called [Black].

So if you want a 100% K that doesn't overprint, simply make a custom CMYK swatch and set it to CMYK(0,0,0,100). Then it won't overprint.

If you place vector graphics from for example Illustrator that contains 100% black, that black won't overprint. That can be annoying sometimes and might require some manual tweaking of the overprint settings or blend modes in the placed document.

Be aware that some printers have their RIP set up to automatically turn on overprint on every occurrence of 100% black! That annoys me a lot because it's out of my hands. A hack to trick such a RIP could be to add 0.5% of one of the other inks. It will probably not be visible on print. A better hack would be to make a white duplicate of the black object and place it just below the black. Then the black will overprint, but you have manually made a white hole for it. Might mess up trapping though. Ask your printer about this if you're in doubt.

As others have mentioned, you might sometimes want a rich black for larger areas. I won't go into that since that wasn't what you asked about.

Answer 2

To set the overprinting of a specific object, use the Attributes Window (Window --> Output --> Attributes) which will allow you to set the overprinting of the fill and/or the stroke of an object. You may need to do the same for any graphics placed in the layout (in Illustrator for example)