White card usage

My last session gave me some new tips that I want to share. Some time ago I was explaining how to use grey card during photosessions. I said back then that one shoot with grey card is enough for unchanging light condition. Unfortunately light condition means also that whenever you change light setup positioning (even same lights) - it might in fact change color ballance. If get yourself into situation like that (for example in studio), whenever you change light settings just remember to shoot also a grey card. Its one more photo that might save you'r butt later on.

Just attaching one shoot from mentioned photosession. On a left I used grey card values from beginning of a session, on the right side I manually update it (cause I haven't got new grey card settings for new light setup). This clearly shows how much yellow value was added by a bit outdated grey card settings.