You guys are gonna slaughter me for asking this...

[Village Idiot]

First of all, AWB shoots in a certain color temp range. That's why you can take a photo outside at night under sodium vapor street lamps and still have an orange frame.

Now what what Derrel is saying in his book there is that an inaccurate WB can cause a color channel to be blown. Think of when you're shooting a live band and one of those blue or red stage lights hits your subject and all you get a blue channel that looks like crap because all of the blue light being focused on the subject and causing the exposure for that color to be blown. That could happen.

My take on WB, especially AWB is to set it for what you're shooting and don't use AWB. If you set it for the light you're shooting in, then you don't have to adjust it in post. This is important if you're shooting in changing light conditions like shooting in doors and out or a live show with real lighting. The AWB won't necessarily be able to handle the color range or having one single WB means you'll have to do that much more work in post. The other reason is if you start using strobes and specifically gelling them, then you'll want a proper consistent WB for what you're shooting.

 

[Robin Usagani]

Well, I typically leave it on AWB, but having it set to certain temperature closer to flash temperature is good because for example you are shooting indoor with a lot of warm lights. Your preview will show how the flash and ambiance light mix. If you see people faces are orange or yellow from the light nearby, then it will give you a warning and you probably want to lower the ISO and make your flash work extra harder. Sometimes you dont see this if you use AWB because it may pick the wrong temperature. If you set the WB too warm then you dont see the effect of flash as much on your preview.