Convert spot colour file to CMYK - Adobe Photoshop

Image -> mode -> CMYK ?

Merge Spot Channel in a CMYK document.

Doing what Cybernetic Nomad suggests may not deliver what you want. If you actually have 4 Spot Color Channels, using Image/Mode/CMYK will separate the 1st channel into CMYK and will also have an additional 3 spot color channels.

I think what you want is to go Image/Mode/Multichannel/CMYK. This will change the apearance of your image, but the correct percentage of each channel will be assigned to each CMYK channel. Then you tell your printer that the Cyan plate is for PMS#1, the Magenta plate is for PMS#2, the Yellow plate is for PMS#3, and Black is for PMS#4. This way they can print it properly.

Is this what you were looking for?

Craig Cheatham

As mike said in Post #2 merge spot channels

select all the spot channels and merge them

....Assuming you have CMYK channels to merge into, and in this case it is really merging into the COMPOSITE CMYK channel.

In a multichannel file you won't have the composite to merge into (even if you have C, M,Y and K channels), and you sure can't simply change the file color mode via Image>Mode.

If you have a multichannel file, copy one of the channels, and bring up a new document but change the mode to CMYK instead of grayscale, then don't paste anything... go to the channels palette in the multichannel file and drag the spot channels one at a time into the new CMYK file... then merge them into the CMYK.

So in this case, there is no real easy way.

Just do what I tell you and it will be alright.

Hey Mike,
Can you get specific about HOW you merge those channels?
I guess this is an area of PS I need to learn more about, but I can't figure out what command you use to merge channels.
Carolyn said that her file was 4 spot channels, so doesn't that mean that it is either a multichannel file, or a grayscale file with 3 spots?
Maybe I misunderstood.

Craig Cheatham

What Mike said was generally correct and what John said was a more descriptive version of what Mike said. Thank you both, since I now have a CMYK composite of the previous multi-channel spot colour file. Which is what I need for other applications.

The one problem is that this new composite looks different from the original multi-channel file on the screen. Is this due to the fact that Photoshop compensates for the fact that basic CMYK can't reproduce custom PMS/special colours?

Thanks again guys. I thought I had tried the merge spot channels command but it was always greyed out.

Mike, John, thanks.
I set up a file and ran through what you said. Works great. I never saw Merge Spot Channel because it was always grayed out, and I guess I just didn't see it, even when I was looking for it. Also, I misunderstood what Carolyn was looking for. I thought she needed to know how to make the spot plates separate out. I've never created spot channels to merge back into CMYK.

Carolyn, Yes the colors look different if the spot colors are out of gamut for CMYK.

Craig Cheatham