CMYK to spot?
January 31, 2008 8:25 PM   Subscribe

How do I convert a CMYK image to spot color in Photoshop? Once this is done, is there any easy way to swap out spot colors?
posted by Brocktoon to Computers & Internet (14 answers total) 6 users marked this as a favorite
as stated your question doesn't make sense yet. you could conceivably tell your printer to swap out the cmyk inks for the spot channels you want to use. what exactly are you trying to do?
posted by patricking at 8:47 PM on January 31, 2008

The second half of your question is "yes", you can just change what ink the channel separates as. The first part is a bit more tricky --- what kind of image are you trying to convert to spot and for what reason?
posted by nathan_teske at 8:48 PM on January 31, 2008

If you answer Nathan's question, you'll likely get a better result...but here's a quick-ish and dirty way to do it:

> turn image to grey scale
> Turn image to Duo Tone
> Change it from Duo Tone to mono Tone (ie get rid of the other color)
> Choose your spot color
posted by Wink Ricketts at 9:22 PM on January 31, 2008

Thanks guys, here's the scenario: client says, "Submit your final design package using spot colors only". Me: using at least one CMYK TIFF image.
posted by Brocktoon at 9:59 PM on January 31, 2008

Without more info the request doesn't make much sense. Generally, "spot color" refers to any non-standard ink added to a standard CMYK or 1-color (usually black) process. Technically, though, you could call CMYK 4-color spot: they are functionally identical. It wouldn't make sense, though, for anyone to refer to it as such as it would just creates confusion.

The only sorta-plausible explanation I can imagine is if the thing is going to get screen printed. In this case they could be using "spot color" to mean that they can't register 4-color inks well enough to allow for full-color reproduction of images. If that's the case then probably any tints of an ink are counted as extra colors, too (though my understanding of screen printing is somewhat limited, so I could be wrong).

Can you give us more information about what kind of piece you're working on, who or how it will be printed, or what other requirements they gave for packaging yr art?
posted by wemayfreeze at 11:48 PM on January 31, 2008

I've had this requirement from print providers, and as wemayfreeze suggests, it's been with screenprinting (eg. tshirts or on-body cd artwork).

Brocktoon, there are a few ways to do it. It depends on what sort of image you're starting with (say, a simple graphic v photograph), how many spots you want (often "how many we can afford") and how you want it to look when printed.

Wink Ricketts' method will work. I'm assuming you need your spots to be pantones, so when you get to the colour picker stage click the "custom" button). You may want to find someone who has a set pantone swatches to help you pick colours, by the way.

Also, there is a 'create spot channel' option in your channels pallette. You could create spot channels (again use 'custom' to get to the pantones) from selections and then delete your cymk channels.
posted by spandex at 3:43 AM on February 1, 2008


If you could post a sample of the final piece so people could have a visual, that might help a lot.

I'm guessing you need your image in a say, just cyan, while the type or other stuff in black or some other color.
posted by Brandon Blatcher at 5:26 AM on February 1, 2008

From what you described, I would not use CMYK. If the image mode is CMYK, you can add spot colors, but you gotta watch all of your channels. We get Photoshop PDFs in all the time, and the black is almost always separating on all four plates; Photoshop's default black is a four-color black. In a spot color situation, if the person processing your image encounters this, they are going to be rather ticked off.

What is probably your most effective option is to add spot color channels to a grayscale image. Change to image to grayscale, and then go to the Channels palette. Click the small flyout arrow on the top of the palette and choose New Spot Channel. (Try to be sure to use the color library the printer will, or at least use the same library for all colors if you don't know what the printer will use. For example, don't use Pantone solid coated for one spot color, and Pantone solid uncoated for another. This can help avoid a lot of confusion when the printer sets the plates.) When the new spot color channel is added, you can paint the color on there the same way you would paint a layer mask, which is to say that black gives you full coverage, white gives you none, and grays give you a percentage. You can actually do some pretty neat stuff this way, and it's worth experimenting with.

You can use the duotone option listed above, but the color is hard to control and can end up looking pretty lousy on some images. (We use this at work for our rare spot color jobs, because Quark doesn't play well with Photoshop spot color channels. One of the many things that makes me wish we'd switch to InDesign...)

If you have the chance, by all means call the printer. Getting their requirements clarified ahead of time will save time, money, and hassle. They do this stuff all the time, so they know what works.
posted by azpenguin at 8:17 AM on February 1, 2008

Thanks again guys.

This is for mail marketing packages to a specific dealer list, and I am generally limited to 4-5 spot colors, so any color intense raster image I want to use must be converted to the spot colors I have chosen to use throughout the package (black of course, and usually red, blue, green, maybe yellow).

Unfortunately I do not interface with the printer at all; only the writer/client.

Azpengiun, I will try your method when I get a chance.

Here's what generally happens; I will finish the package and then go back and try to manage the colors, so I will look at the InDesign swatch palette, delete unused swatches, and try to figure out how to get rid of the CMYK. If I used a color intense raster image, I will always see it's CMYK values in my InDesign palette, and I'm sure this is what the printer will see as well.
posted by Brocktoon at 10:43 AM on February 1, 2008

what shows up in InDesign's swatch pallet is not necessarily a good representation of how your file will separate. A better soft proof is to export an X1A PDF and then view the seps in Acrobat.

It sounds like you're doing a lot of colorbreaking in your CTs. It might be better just to design around the non-CMYK pallet or let prepress do it
posted by nathan_teske at 11:37 AM on February 1, 2008

In that case, I'd try adding spot color channels to your CMYK image using the spot colors you're using in your layout (using azpenguin's method above) and copying and pasting from each CMYK channel to the most-similar spot channel (cyan to blue, for instance). Delete the CMYK channels and you'll end up with an image that uses your spot colors and looks more-or-less okay. You can then play around with the levels/curves of each individual spot channel to get the image looking like you want, though you'll have to play around a lot and will probably have to go for an artistic—rather than natural—look; recreating a CMYK image with non-CMYK inks will be pretty difficult.

I have no idea if this is an approved way of doing this. I've never used it except for playing around in the last hour trying to answer this question!
posted by wemayfreeze at 11:41 AM on February 1, 2008

On further thought, though, if you're allowed 4-5 spot colors—unless there's some missing piece to the puzzle—you should be able to use CMYK, right? Is there any reason why cyan, magenta, yellow, and black can't be your 4 spots? And switch out your other spot colors for the process equivalents?
posted by wemayfreeze at 12:53 PM on February 1, 2008

Wemay; I'm told from another client that CMYK is more expensive to produce in this application, and then of course I must revert to my client's demand: "Use spot colors only", which I take to mean "do not list any CMYK values on the transmittal sheet, because you should not be using them".

I should really charge extra for this, if I'm spinning my wheels for nothing! Where's the "convert to specific spot colors that I want to use" button in Photoshop?! ;)
posted by Brocktoon at 1:38 PM on February 1, 2008

I guess it just doesn't make sense to me that you'd not be allowed to use CMYK but using 4 other inks as if they were CMYK is OK. Which, again, suggests that they may mean something different when they say "spot color."

Anyway, good luck! If you find anything else out I'd be curious to hear about it.
posted by wemayfreeze at 2:48 PM on February 1, 2008

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