灰卡（卡纸的一种）英文怎么说？

灰卡 Grey Paperboard

同样，以此类推——

白卡White Paperboard
黑卡Black Paperboard

Grey Scale

Gray Card

Gray Card
What is a gray card?
Camera light meters see reflected light, but it is often useful to know the incident light (the light hitting your subject). With an 18 percent gray card you can get a reflected light reading which is essentially the same as reading incident light. Our gray cards are made from mat board. They have been painted to give results similar to an 18 percent reflectance Kodak gray card. This is equivalent to zone V. In the zone system, V is the middle tone half way between black and white.