Black and white vs. color

Question

This is more a general printing question than an ID question, but here goes. I'm a newbie to printing. I'm just fooling around with ID, getting my feet wet for some eventual projects, and my question has to do with color. If I create an ID document that contains color and then send the document to a printing press (either as a native ID file or a PDF), but with instructions to print in black and white, what happens to my color images if we're not printing in color? I know that the correct thing to do is make sure that every photo is converted to grayscale before going to press, but I'm just wondering what happens in reality if a black-and-white printing project encounters color information? Thanks for considering this newbie question.

Answer 1

A lot has to do with how the printer's prepress department handles the file,
and what the capabilities of the RIP are. Somewhere some how the color data
needs to be interpreted and converted to best possible representation using
only the K channel. In our shop, if a customer sent an RGB or CMYK file that
would print on press as black only, we would convert the file to grayscale
in prepress. If it was a PDF, we would use Pittstop or Acrobat's built in
color conversion function. If we got an ID file, we would either export as
PDF and do the afore mentioned procedure, or send as a cmyk file and allow
our RIP to change to grays. The latter is a bit risky as you really don't
know what you get until it's on press or a rip proof file is run, both of
which involve costs. And depending on the complexity of our prepress doing
this work, it would probably involve some charges.
Best to do the conversion to gray yourself.