How to convert grayscale bitmap to one CMYK color in Photoshop?


How do you convert a grayscale bitmap a to one CMYK color in Photoshop for printing, eg. C61, M41, Y58, K16 green?

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11/21/2012 10:48:00 AM

Accepted Answer

The easiest way to do this is to open your image in grayscale mode in Photoshop (or convert to grayscale mode if it opens it in RGB/CMYK format).

From there, choose Image->Mode->Duotone.

Make sure the type is set to Monotone. Ink 1 will be set to black. Click on the black box, to access a color picker. Choose the color you want (use the color libraries button to get to the list of Pantone colors.) Click okay, and you are done!

Here's how it would look using the RGB values you specified.

Using the RGB values specified to make a monotone image

11/20/2012 6:52:00 PM

For completeness, I'll add here that is not always necessary to alter the greyscale bitmap file. If it is in TIFF format and greyscale, and you are using a layout program (indesign, Quark, foo etc) you can use your layout program to tint the image to an exact swatch.

For indesign, you place the image, set the background color of the box to whatever (paper, black, red, purple etc), and then switch the context to the content of the box (aka the image is highlighted brown) and set the foreground color.

The greyscale image essentially acts as an alpha channel for the foreground color. (does not involve clipping paths etc.)

I like this method because it does not alter it (same as the accepted answer,which I upvoted), and it also ensures that the layout program uses the same CMYK or spot color values as all other items in the document (eliminates any chance of a profile or {magic} color adjustment).

In addition, if you change the swatch, it cascades the change throughout the document without the need to edit individually placed files.

Additionally in addition, you can use the same image without alteration with muliple color values. (Think Andy Warhol)