Convert Multichannel to CMYK in psd CS

[Mark_Crommentuyn@adobeforums.com]

I have a document in three multichannel PMS colour I want to convert the file into CMYK but this is not possible.

When I ad a channel I have the option to make a CMYK document.

But it doesn't covert the color to CMYK it place the PMS in to the cyan magenta and yellow channel.
I want that the colours a build up in CMYK

[Ann_Shelbourne@adobeforums.com]

You don't mention what Pantone colors you are using but try pasting each plate separately into the most appropriate C. M or Y channel in a new Multichannel document; converting to RGB and then to CMYK.

[Greg_Kolakowski@adobeforums.com]

I have had to do this before. I took a 2 spot color multichannel image in Photoshop and PRINTED it as a PDF file NOT saved as a PDF file (this should convert it to a RGB image) then you can open the PDF in Photoshop and convert it back to CMYK mode.

[Ann_Shelbourne@adobeforums.com]

Brilliant solution, Greg.

"Printing" to a PDF produces a very clean replica of the screen-rendering of the spot colors (translated into RGB) and you can then make a seamless mode change to CMYK.

[John_Slate@adobeforums.com]

....or you can get the spot channels into an otherwise blank CMYK file (you can drag and drop), then use the channels flyout to merge each spot into the CMYK. That method will convert to the CMYK build based on whatever Pantone color book you are using, and will vary from the other methods a little bit. Can't say which is better.

Simply adding a 4th channel and converting to CMYK will not even be close. It's not even a conversion.

All that does is rename the 4 channels so that the top is C then M then Y then K. Or in other words if the top channel is PMS 200 red, then that channel will become cyan.

[Schauk]

1. Create 3 Alpha Channels
2. Invert them to become white
3. Bring them up in the channels panel
4. Convert the image to RGB
5. Select all channels and go to the panels menu and choose Merge Spot Channels