Originally posted by slackercruster WOW...your hard core!
LOL, I started with the white card in my bag due to a couple of venues i was covering shows at converting to LED ligh, and then deciding they liked purple light. unfortunately that means no greens for the most part and losing 1 channel of colour sucks. the cards weigh little so I just leave em in the bag, and either set wb with them, or at least have a file shot with one item i know the values on so i can correct a group of shots. for some reason Pentax' software repopulates the green missing in the LED example i gave, so i keep it on the computer just for that (LR doesn't)
Otherwise i just look for something white in a scene and fine tune the balance, I always shoot raw anyway