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18% Gray Card

18% Gray Card

An 18 Percent Gray Card is a simple gray-coloured card which uniformly reflects 18% of the light which falls upon it. Gray cards can be used as a reference to set the camera exposure or to calibrate a light meter (light meters are used to determine which exposure setting is required to produce a medium gray tone).

Gray cards are usually made from coated cardboard or polystyrene and come with a protective cover. They are an inexpensive and useful addition to the photographers' kit.

How to Use a Gray Card

To set your exposure with a gray card, first make sure the camera is in manual mode or is able to hold its settings when you half-depress the shutter button.

Position the card immediately in front of the subject, ensuring that the lighting on the card is exactly the same as the lighting on the subject. If you are using a light meter, take your reading now. Otherwise, half-depress the camera shutter button to save the exposure setting until you fully depress the button (and take the picture).

(Note: This process is very similar to performing a white balance).