Grey Card is a tool that allows a photographer to measure the degree of light in a given scene. This piece of photographic equipment is uncomplicated and non-mechanized: it generally consists of a piece of matte cardboard colored grey, as its name suggests.
The dimensions of grey cards tend to be 8 x 10 with an eighteen percent reflectance value. When placed in a scene, grey cards are a solid indicator of the exposure factor, the amount of exposure the resulting photograph encounter. Similarly, a grey card can also be placed within a frame to balance color.

If you are unsure of how to work your camera’s exposure meter, pick up a grey card to help you measure a scene’s amount of light. When using a grey card, be sure to keep the card as vertical as possible to obtain an accurate reading of the scene’s light.
Some situations that may require the use of a grey card include:
- a scene with backlighting or bright window/sky lighting
- a scene with primarily dark central objects and tones, such as a black cat in dim lighting
- a scene with primarily light central objects and light tones, such as a polar bear in a snowy location.