The ExpoDisc (4x5.65") brand_Lensmate and it all folds down

and it all folds down to a relatively thin slab with iconic leather-and-chrome styling

all-metal ball head with a uniquely designed elliptical ball that naturally increases tension as the ball goes off-axis to help you keep positioning control with heavy gear

and checked it's accurate to within 1/3rd stop accuracy from LV5 (1s f8 200ASA) to LV15 (1/1000s f8 200ASA)

it also has a fast f4 constant aperture and Canon’s premium L-series optics

The ExpoDisc (4x5.65") brand_Lensmate and it all folds downThis particular Expodisc is not a disc it's a big 4x5. 65" slab designed to slip into matteboxes but it works the same as the classic. Basically, it's a specialized flat diffuser designed to facilitate setting custom white balance. Rather than hauling around a gray card, or trying to find a plain white surface, or hoping that your camera guesses correctly, you can toss this in front of your lens and lock in an accurate custom white balance in seconds.