Convert from RGB to CMYK in Photoshop: Deke’s Techniques

Published by | Tuesday, August 20th, 2013
Converting RGB to CMYK with Photoshop Multichannel

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Welcome back to Deke’s Techniques. This week, Deke shows how to convert an image from the RGB profile to CMYK—a process designers often need to go through when they’re sending their work to be printed commercially. However, Deke’s spin on this technique is an unconventional method that preserves more of your luminance data, using the Multichannel mode in Adobe Photoshop. Click the video below to start learning. members can also watch the followup video in which Deke shows you how to tone down the shadows in the new CMYK image to make sure they’re printer–safe. Come back next Tuesday to learn how to add a motion-trail effect to your photos.

Interested in more? Check out the entire Deke’s Techniques tutorial series at

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One Response to “Convert from RGB to CMYK in Photoshop: Deke’s Techniques

  1. I would not recommend this procedure for normal commercial printing. There’s a very good reason why the Cyan, Blue, Magenta, and violet values vary so much between the “correct” Adobe method of doing the colour separation, and your method. For example, 100% blue on a monitor (in RGB space) appears quite bright and pure. 100% Cyan, 100% Magenta, which your method converts this blue into, is a deep dark purple colour when printed on a page. It is actually impossible to “print” pure RGB blues or RGB cyans on paper using commercial process ink colours, so the modified, desaturated versions of these colours are an attempt at preserving the intent of the colours. Printed Cyan ink is far darker and somewhat bluer than RGB Cyan is on a monitor screen – you cannot equate them as your process does. This is why the normal conversion process is more desaturated and somewhat “greener” – it’s trying to emulate the intent of what the colour looks like on the screen.

    It also appears that you are comparing your method with the standard method by using inkjet printer output. I have no doubt that if you had output the toucan image and colour swatches on a commercial offset press with standard US printing inks, the resulting image would have been very dark and muddy. Inkjet cyan != SWOP cyan, inkjet magenta != SWOP magenta. SWOP colours are not pure – cyan is “bluer” than it should be, magenta is “redder” than it should be, and yellow is “redder” than it should be. Adobe’s method is an attempt to compensate for this. Ignore years of research into colour separation methods at your own, and your client’s peril.

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