While my understanding of all the possibilities of calculations is limited,
The only ones I really bother with ( thanks to an old post by Steve V )
do little more than 'select part of a channel and add/subtract from another'.
Having said that, I'm still monkeying with a seperation prepping thing.
Calcs make for a much cleaner looking action script.
Just be aware that most calcs are just a reproduction of what you'd do 'by-hand' when sepping.
Like..instead of picking a channel, making a selection, selecting and/or duplicating another channel,
then adding/removing the selected data from it, etc.
All meat and potatoes one needs to understand in any piece of software.
Once you get that stuff figured, calc away.
Photoshop is fairly straight ahead.
You'll get it all figured if you use it enough for awhile.
