Trying to build a 2-color ad
Kim Schmidt from Virginia, USA, using Photoshop CS with PC - Windows XP, writes in with:
[Quote:] The Task - Take any color photo and make it one color (magenta) for a 2 color ad (black and magenta). What I did - I changed the photo's mode to grayscale. Then turned it into a monotone file using the picker to select magenta only. Question - Why then, when I use the eyedropper tool, does it break the picture down into CMYK? The publication said it was still a 4 color file and therefore couldn't be used. I ultimately ended up using channels to remove the CY&K, but I've never had to do this in the past. Isn't the point of monotone to eliminate all other colors except for the one? HELP?? Thanks, Kim
As David Blatner says in his "Real World Photoshop" book,
"We've always felt that it was a particularly cruel joke by the programmers to offer people the chance to pick spot colors without also offering the opportunity to print those colors out on spot-color plates."
He was referring to what we all know as the rule "Don't Pick Spot Colors" -- painting with a "spot-color" does not give you a separate color plate, but rather breaks the color into CMYK.
Use Spot-Color channels for ALL of the image information.
Save the file as DCS 2.0
Choose New Spot Channel from the pop-out menu on the Channels Palette. Leave the naming to Photoshop in the resulting dialog after selecting your color. (If you don't it won't match once they put it in their Quark or InDesign file! To be safe, tell the service bureau what you've named the channels, or actually send along the native Photoshop file so they can make sure.)
Put no information what so ever on the RGB or CMYK channels.
This is best left to a professional. If you are called upon to do this frequently, and wish to learn the correct (and lengthy) way to accomplish this, you should get the Real World Photoshop book. It's probably the best book for those who actually use their Photoshop files for commercial printing.