InDesign: Black Prints as Gray

InDesign Help had an article about this problem, where you think you're printing black, but it's coming out of the printer as gray.

Even worse, the blacks in the images come out black, making your gray look ugly!

Solution is to go to Edit->Preferences->Appearance of Black

Set On Screen to "Display all Blacks Accurately"

Set Printing to: "Output all Blacks as Rich Black".

Rich Black is a black produced by combining CMY and K into black. I think the normal thing to that happens is, black gets replaced with 100% K ink (black ink), which is actually a little bit gray when viewed next to Rich Black.

(Just to confirm, I looked at some offset-printed pages on glossy paper. Indeed, black ink looks lighter than black ink combined with another ink! You can see this by comparing a black graphic with a color graphic overlaid with some black text. The black text doesn't knock out the color ink -- the software is probably trying to avoid registration problems that would show up as white edges on the letters.)

Once you do that, InDesign seems to convert all blacks to have 100% K. But if you manipulate the color, you'll have to adjust the color. That's what worked for me.