Gray Card Selection

Almost all photographers are very familiar with using an 18% reflectance gray card to set the camera’s exposure. Usually these are used by placing the gray card into the scene and pointing the meter or camera at the card and setting the shutter speed and aperture for the exposure. The color balance needed to achieve neutral gray tones in the image is determined by the film manufacturer, set in the balance of the cyan, magenta and yellow dyes in the film. The closest comparison to the film emulsion in a digital camera is the sensor. However, unlike film, the digital sensor is not created with a particular color balance. The balance is determined by the camera circuitry. Some digital cameras have predetermined color balances for different lighting situations such as direct daylight, indirect daylight, flash, tungsten or fluorescent illumination, or a method for automatically adjusting the color balance.