Binary FX: Photoshop Tech Vault 3.0

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Mask from Ten Image Channels

How To:

Create a mask based off the three colour modes and ten channels.

Although Dan Margulis is famous for avoiding the use of selections and masks when colour correcting images, this does not mean to say the he never uses them. Dan recommends that one explore CMYK and LAB versions of an RGB image when looking for masks or channel blends, as the vastly different AB channels found in LAB mode offer further possibilities for image correction above and beyond the RGB and CMYK channels.

Creating the 10 Mask Channels:

Create a duped file from the original RGB file and convert to LAB mode (pay special attention to the A and B channel content). Duplicate the RGB file again and convert to CMYK mode. The K plate and thus the CMY content which is linked to the black data can be generated in many different ways depending on the chosen profile or Custom CMYK settings.

Automating with Actions:

A special thanks goes to Danny Raphael at RetouchPro for this Photoshop 6 action which makes the task of quickly creating and viewing the ten channels from the three common image colour modes painless (The K channel can be generated in many ways using the legacy Custom CMYK command in Colour Settings). The action will create the 10 channels and display the windows in tiled view. Using synchronised window pan/zoom in Photoshop CS (shift+hand tool) or later and a large monitor is recommended.

Update: The Light's Right also has a similar action available for download, which may be more convenient than joining RetouchPro.

RetouchPro - Split Channels Action Link | TLR Digital Darkroom - TLR Split Channels Action Link | http://members.ozemail.com.au/~binaryfx/Split_Channels.zip

Further Information:

There are many cases where a mask or selection may be required and performing blending tricks to avoid the creation of these masks may not be possible. The problem with selections and masks is that they need to be very good, otherwise the edits may look artificial. Where possible, using the existing image pixels found in one of the three colour modes channels provides a quicker and more natural appearing selection or mask than one that has been hand drawn, although there are of course exceptions when one may prefer a more clinical edge over the natural mask offered by the image channels. The Apply Image and Calculations commands combined with layers and Blend If sliders are excellent tools for combining channel content from different colour modes into a mask that can be further refined with toning or painting tools.

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