The Digital Photography Companion



EXPOSURE MODES BASIC

53

the exposure right. e green grass is much closer to the magical 18% gray for which

exposure meters are calibrated.

e solution is to lock the focus on your daughter, and then to point the camera at the

grass and press the exposure lock button. You’ve just instructed the camera to focus

on one part of the scene and to measure the exposure from another part. e result: a

beautiful portrait of your daughter.

You can use exposure lock as a shortcut for exposure compensation. Instead of access-

ing the exposure scale and adjusting your image that way, you can find a middle tone

in the picture you want to shoot, such as a patch of grass, and lock your exposure on it.

is is a faster way to override your camera’s autoexposure setting in difficult lighting

situations.

If you find that you’re mostly interested in using exposure lock for people shots, you

might want to consider using face detection instead (as covered in this chapter). Not

all cameras have face detection, but if yours does, it achieves the same results as focus

lock, but more quickly.

Exposure Metering

Most digital cameras rely on programmed automatic exposure metering to determine

the best aperture and shutter speed for a good exposure. Essentially, the camera’s light

meter reads the light and compares the data to a set of instructions stored in the cam-

era’s memory. e camera ...