I added this Before & After so you can see the difference a grey card can make. Both images are completely unedited just the white balance was added to the After pic. I use Lightroom 5 for processing and simply use the eyedropper tool, drop it on the grey card and click and you can see the color balance is more accurate to what I remember the model looking like. The grey card I use is no bigger than a credit card and was about $8 and makes editing so much faster, more accurate and gives you a better place to start editing. Hope this helps.