How can I prepare a bitmap image to print in black & white plus one spot color?

April 29, 2008 8:43 PM

How can I prepare a bitmap image to print in black & white plus one spot color?

I'm doing an illustration for a magazine, and I've been given the instructions that it will print in black plus one spot color. I've scanned a drawing into photoshop (b & w) and created another masked layer with the specified spot color. My contact at the magazine does not know how to set up a photoshop file to print black & white with the one spot color. I tried creating a duotone (black plus the spot color) but that seemed to require tinting the whole image with the spot color, when I want some areas to be tinted, and some not. I tried creating a cmyk file and adding a spot channel, which allows me to tint the image selectively, but I'm not sure if that's the way to go. I'm waiting to get more info from the magazine people, but in the meantime, if you were asked to prep a bitmap (not vector) file to print in black & 1 spot color, how would you go about it? Thanks! (mac, photoshop cs3)

posted by pantufla to media & arts (6 comments total)

Could you flatten the image and simply save as a .tiff (or any format they want to work with)? I don't see why you'd want to keep the color on a separate layer once you're done. As soon as you have a color, it's not black and white anymore.
posted by ddaavviidd at 9:45 PM on April 29

The thing with the CMYK+1 sounds about right. You can delete the C, M, and Y channels, too, so you'd just have K and [color].
posted by Plug Dub In at 10:03 PM on April 29

Plug Dub In has it. To add to that, you cut the entire image, convert to CMYK, paste the images on the K channel only. Then you can paste the image again on one of the other channels and edit as you see fit. That would create a two-color CMYK image that, when separated, would only produce two plates with data on it.
posted by tcv at 10:37 PM on April 29

Open your image and convert it to grayscale. Then, go to the Channels palette. There's the little arrow in the upper right of the palette; click that, and then select "New Spot Channel." In the dialog that comes up, you can select your spot color by clicking on the color. If you have a specified Pantone color, you can choose that by clicking "Custom" when the color picker comes up when selecting the spot color for the channel. Once the new channel is created, you can paint the spot color on and off just like you would a layer mask.
posted by azpenguin at 11:21 PM on April 29 [1 favorite]

azpenguin has it -- save the file for output as a Photoshop EPS when you are done. Don't use TIFF or a layered TIFF.

(Plug Dub In, with your method, there's no way within the file to spec the spot color.)
posted by omnidrew at 7:05 AM on April 30

Thank you all!
posted by pantufla at 3:58 PM on May 3