RGB to CMYK the Device Link way
We've built a reputation for creating CMYK files that maintain as much colour and detail as it is possible to get from the original RGB.

Unfortunately this usually entails a lot of time-consuming effort in Photoshop, converting the images using different rendering intents and then creating a single image from the best bits of multiple separations.

But we've now developed a better way. And a faster way of getting the best possible CMYK conversion from an RGB original.

Device Link Profiles

When you carry out a conventional colour separation in Photoshop your image is first converted from RGB to the L*a*b colour space using the embedded profile to determine the L*a*b colour values (or your working space profile if you are crazy enough to work with un-profiled RGB images).

The L*a*b values are then converted to CMYK using the destination ICC profile and your chosen conversion intent (perceptual, relative etc) to determine the final colour values.

The problem with this approach is that the Profile Connection Space -- the L*a*b values that sit between the original and final images -- dislocates the colour values and causes them to be recalculated from scratch when retaining some of this information might be useful.

This is apparent if you find yourself converting from one CMYK profile to another. If you've spent ages retouching the original image to set specific colour values you'll see them get changed during the conversion -- especially pure primaries.

A Device Link Profile is a special class of ICC profile. Unlike other ICC profiles, it doesn't describe a specific device but a conversion formula to transform an image from one specific profile to another.

Steering clear of conversion to the L*a*b Profile Connection Space means that you not only get the best result but also avoid common problems like banding in gradients, contouring in colour transitions and impure primaries.

The only problem with Device Link Profiles is that you need specialist software to create them. You also need specialist software to apply them because Photoshop can't use them :-(

Commanding the command line

Just because Photoshop doesn't do device links doesn't mean that you can't enjoy the benefits. The Mac Operating System can do device link conversion -- you just need a bit of AppleScript to get it to do it.

Our favoured solution is using a whole new Colour Management System (CMS) which is controlled by typing commands in the Terminal.app.
 
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