The influence of subject's luminance on the exposure

When a flower of high luminance is photographed, the overall image will be slightly underexposed

Surface reflectivity is not the only way a subject can influence an exposure. The color of the subject is also a factor in causing the luminance of the digitally photographed object to differ from what actually meets the eye. White and yellow have high luminance (reflectivity), whereas blue, brown, and black have low luminance.

When the automatic exposure program of the digital camera determines that the subject is bright, it automatically compensates by reducing the exposure time, with the result that white can become gray, and generally things look darker than they are in real life. The opposite happens with dark subjects; the AE (automatic exposure) program will increase the exposure time and the resulting image will be brighter than in real life. An awareness of these changes in exposure time will help you anticipate a certain type of photographic result from the digital camera. If the camera permits exposure compensation, bracket the shot by taking several different exposures, checking the results, and making necessary corrections.

When a flower of low luminance is shot, the overall image is somewhat overexposed