A-Digital-Eye have published an enthusiastic review of the Expodisc, which is a filter that goes in front of the lens and is used to set a custom white balance for your digital camera. Prices vary from $79.95 to $159.95 (plus shipping) depending on the filter size.

“Most new digital cameras manufactured today now have a custom white balance setting. Instead of using a grey card or a white sheet of paper to set your custom white balance, simply use the ExpoDisc on your lens aimed at the light source to set the custom white balance. The ExpoDisc has prismatic lens on front to collect light from 180 degrees, allowing it to collect light from all around.”

Website: A-Digital-Eye - Expodisc Review

Website: Expodisc