This is a nifty little accessory that helps set the proper white balance on your dSLR's. The Canon requires more steps to set it as opposed to the Nikon, but the end result is the same. I introduced Will (jst1tym) to this when i mentioned his white balance was a little off and he's been using it ever since. Sure one can fix it with photoshop, but if you can do it in camera it'll save you time. I've used other forms of white balance accessories and this it the best/easiest that i've found. The Expodisc requires you to position yourself where the subject is and aim at the light source to set the white balance. The Expodisc didn't do as well as the CRP when there were different light sources either.