Question about CMYK plates

[Greg12]

We had a debate in yearbook about color and black and white.

Me, knowing that black is a component of color, i think that a printing press set with cmyk plates to print color pages can also print greyscale, but a printing press set to greyscale cannot print color.

Am i wrong?

The debate came about because we left out some baby pictures and i wanted to put them on a color page, but covert the images to greyscale because the other ones were. Now the teacher said no because it was a color page, but it seems to be that cmyk printing plates should be able to do greyscale.

[thayne]

You're right. You pay more for color though...

Black is:
C=0%
M=0%
Y=0%
K=100%

[The village idiot]

If it is a color page, and you are using a digital method to send the page to the printer, then a black and white image should be RGB/CMYK just like the rest of the page. If the entire page is grayscale, then all the images should be grayscale, unless the printer wants them to be RGB/CMYK. Almost any layout software will have to convert the grayscale image to RGB/CMYK before you can composite it onto the otherwise color page. So this really should be a non-issue. Depending on how the printing press does it's grayscale images on color pages, you may end up with a better grayscale image. It all depends on whether they use CMY for gray tones, or if it would default to just black ink, you may have to specify light GCR. GCR - Gray Component Replacement substitues black ink for gray portions of a color, allowing the use of less CMY (see this http://www.prepress.pps.com/ColorTips/ColorTips4.htm ).

So in short, just make/convert that black and white image a full RGB/CMYK image and place it on the page.

If your printer still makes a photo of the page that is then used to make the plates, this is of course another non-issue. You give the printer finished pages on paper, he makes the photo, then burns the plates. Most modern printers have gone to a direct computer to plate method, so they are most likely looking for postscript files to use to make the plates.

The only official way to get the correct answer is to call your printer and ask how you should present that page. If I was printing a color proof from a page that had color images, and then a black and white image was added, I would expect the B/W image to be a full RGB/CMYK image. I also doubt that the scanner you are using is grayscale only, considering that you already have color images.

[The village idiot]

I just re-read your post.... So you have a color page, but it only has grayscale images on it? If it only has grayscale images, why is it a color page?