Jack,
Does PE3 have the equivalent of Channel Mixer which I find to be very
helpful in compositing?
While the channel mixer is not in the standard adjustment layers offered in PE3, the functionality is buried in there.
You can get access the built-in channel mixer functionality through use of a free tool from either Paul Shipley (
http://member.melbpc.org.au/~pshipley/) or Grant Dixon (
http://www.cavesofice.org/~grant/Challenge/Tools/index.html)
PSE will honor the settings you make using the channel mixer adjustment layer but it will treat the layer as though it were a photoshop created layer in a file you opened and not allow you to edit it once you exit the dialog box.
As Colin mentioned, The Hidden Powers of Photoshop Elements 3 book also has tools to provide channel mixer functionality. They don’t use the channel mixer, instead, they are custom crafted tools that allow you to achieve the same results. In some ways, you have more control and flexibility than with the channel mixer.
Bob