This Focus Board has two sides, one is 18% grey with target "+" mark, the other side is white. * All grey, target "+" mark and white surfaces of this focus board have their own function. Whatever you used in film or digital photography, the 18% grey side can control expose value, the white side can balance the color and the target "+" mark can provide accurate center photometric. * This focus board helps to revert the color truly and perfectly by measuring the exposure value, white/grey balance value and color temperature. * It is the ideal accessory of the portrait, flower and conversion shoots * Material is PU, could be cleaning with water