Using the ColorChecker Gray Balance Mini for reflective spot exposure metering will give you the confidence that your images will be exposed as accurately as possible. The ColorChecker Gray Balance Mini is a pocket size version of the 18% grey reference square in the standard 24-patch ColorChecker. The grey is scientifically engineered to provide a precise uniform surface that is spectrally neutral, meaning it reflects equal amounts of red, blue and green in all types of light conditions.