Black and white vs. color

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.
Black and white vs. color
Depends on the printer. Any printer should call you when given a colour file for black and white printing. You should expect that colours will be converted to grayscale equivalents, which is usually not ideal. To get an idea of how that would look, export a PDF and open the PDF in Photoshop as a grayscale image.



If you care a damn about how the printed job looks, take the time to get it right. convert any vector elements (Illustrator files, or text and objects in InDesign) to either gray values or black and white. Open images in Photoshop and use a Channel Mixer adjustment layer to modify the way colours in the image are converted to grey values.



Colours that have high contrast against each other often become very similar when converted to greyscale. A yellow sunflower against a blue sky looks great in colour, but the grey value of the yellow might be too close to the grey value of the blue.



Moral of the story: assume nothing.
Black and white vs. color
What happens when you put a color document on a B%26amp;W copy machine? You

get grays. Same thing in printing. Either way, though, it's impossible

to envision what you're going to get until you see it. If the colors are

important, you're going to want to convert to grays first, so you can

adjust it if necessary. For instance, I'm working now on some graphs.

The author made them in Excel and used color to differentiate the bars.

When I convert these to grays, some of the grays are almost

indistinguishable, so I have to spread them out or use patterns.



--

Kenneth Benson

Pegasus Type, Inc.

www.pegtype.com

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.

clarins