Well, the grey card is to set ur exposure. "U cannot compensate for ur camera's inaccuracies to match the scene unless u know how far from the average the scene is. This is very difficult thing to judge so the answer is to give the camera what it expects to see, the prevailing light falling on ur scene bounced off a surface which reflects 18% of light in all colors, an average reflectance, average grey: a grey card!". But apparently, most scenes fall into the average but some scenes don't, like darker scenes or snow scenes and stuff and that's when the grey card is becoming handy! So I guess I've just answered my own question here and that is to use the grey card in less than average scenes only! Well, I hope so! Michelle? Help? PLz! ;)