Using the ColorChecker 18% Gray Balance target for reflective spot exposure metering will give you the confidence that your images and video footage are exposed as accurately as possible with the same 18% gray reference square found in the 24-patch ColorChecker Classic target. The gray 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 lighting conditions. The perceived color of white changes based on ambient conditions