Quote (Sprak @ Sun, 16 Aug 2009, 19:20)

you choose whatever channel has the highest contrast and then multiply it through image calculations

if the stock isn't already on a one color background, then you brush around it to make it one color which makes it easier to work with channels

a lot of professional photo shoots have models on a plain background so it's usually easy to render... there are obviously varying circumstances which need adjustments

but rendering hair is by far easiest in channels