graphicxtras.com > Photoshop shapes used with channels, RGB channels red / green / blue etc tutorial
Apply a Photoshop shape as a 'fill pixels' option to one channel, apply a shape to another color channel, combining Photoshop shapes across channels creating stunning RGB images.
1) Select the custom shape / CSH tool
2) Select channels panel
3) Select fill pixels (for shape) - top bar
4) Select one of the channels only (say RED)
5) Apply current selected artwork to RED channel
6) Select green channel
7) Apply current selected artwork (you don't have to use the same artwork), perhaps offset from red design (or smaller or apply effect as well)
8) Click RGB on channel panel to return to standard RGB view
You can also use the RGB channels (as well as LAB channels and CMYK channels etc) to use visual effects to each channel in turn. The vector CSH artworks can be added just as easily to the Lightness and a and B channels of LAB Image mode as well as the cyan and magenta channels etc of the CMYK image mode. You don't have to use all the channels either, you can use the Lightness only and ignore the AB ones.
You can add the artworks to the the various channels via the the panel but you can also work with them split into individual files for the red and green and blue channels. You can split them into individual files via the right side menu. The only thing, the split does not add the files as RGB etc but adds them as grayscale which is of little use if you wish to use the artworks with various effects that can only be used in RGB etc (and will not work in grayscale). You can resolve that by going to each of the red and green etc (or cyan and magenta) and changing the image mode to RGB via the image menu and then adding the effects and additional vector paths to the artwork (the advantage of the split is also that you can then use them as layers instead of just pixels and then you can add styles into the mix). You can then use the merge feature (right side of the panel) by selecting the mode (RGB etc) and number and then select which file is used with each channel in the merge. You can, of course, also add to the RGB as well as the red and green etc
A quick video showing some uses of the Photoshop shapes and channels [Youtube]