A very helpful tool for achieving accurate color in challenging lighting conditions, the ExpoDisc V3 Wide Spectrum White Balance Filter features an updated design with a more compact, slimmer form factor, redesigned attachment system, and revised diffusion materials that perform better across the visible spectrum. The ExpoDisc can be used to set an in-camera white balance using your camera's custom white balance procedure. With your camera on manual focus mode and the desired aperture set, simply hold the ExpoDisc in front of your lens, point the camera toward the same light illuminating your subject, and shoot. Use this image as the reference when setting white balance on the custom white balance function in your camera's menu. It can be comfortably held in front of your lens, or attached via the bayonet mount, and it fits lenses up to 77mm in diameter.