1、Play the role of gray board, also suitable for automatic and manual lens practice at the same time. 2、18% standard gray, gray board one side, with assist focusing scale, whiteboard one side, good tool for tuning white balancing, with portable bag. 3、Focusing board is the benchmark for accurate detection. Rich gradation, colourful saturation pictures come from accurate exposure. Exposure to lighting may have deviation if the light of the scene is too bright or too dark. 4、Focusing Board can make complicated light scene to change to the 18% neutral gray, through the light meter record the focusing plate reflected light, can get accurate exposure value. 5、Focusing plate can used to measure the exposure value with hand-held light meter, TTL SLR camera, digital camera and side-axis camera with light metering. Using trichromatic focusing plate is guarantee of high quality photography.