Hand-held reflected light meters (including built-in camera meters) read the intensity of light reflecting off the subject. Because they measure the light after it hits the subjects, however, they are affected by the reflectance of the subject's surfaces. Also, because most reflected readings are taken from the camera position, they generally take in a wide area that can include many different reflective surfaces or colors that can bias the meter reading. If you're photographing a person walking on a sandy beach on a bright day, for instance, the light reflecting off of the sand will overwhelm the reading and result in an underexposed image of the person. A reflected meter will provide different readings for say, a white cat and a black cat—but it will provide an exposure that records both as the same middle gray. Similarly, a pristine fresh-fallen snow and a black coal field will be recorded as the same color: medium gray. A reflective meter will also record a red apple and a green apple as the same tone — even though in reality they reflect vastly different amounts of light. You can improve the accuracy of your reflected readings by placing an 18-percent neutral gray test card in front of the important subject areas — but that's not always practical.