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172 The “Recording” (Camera icon) Menu Settings

Handheld exposure meters work on a completely different principle than
the ones built into your camera: Handheld exposure meters measure the
light that

12 images 400 images Thousands of images

Figure 5-31: Average subjects in average scenes reflect back about 18% of the
light, and so that’s what your camera tries to create – it is assuming you’re
shooting an average subject. As an interesting experiment, when you average
together hundreds and thousands of normal snapshots, you will eventually end up
with an image that’s about 18% grey.

is falling onto your subject. Built-in exposure meters, on the other hand,
measure the light that is reflected off of your subject and back into the
camera.
Is this a good idea? Well, yes and no. No because the reflectance of the
subject will vary wildly – brides in white dresses, for example, will reflect
much more light than, say, a groom with a black tux – and therefore your
in-camera meter will give you wildly different values. Yes, because it’s
infinitely more convenient to have the camera guess the right exposure than
to go over and measure it with a handheld meter. And besides, for average
subjects (like pictures of anything except brides and grooms ) the
reflected method works reasonably well.
More detail: The camera has absolutely no idea that your subject is bright
or dark; white or black, or yellow. Once upon a time, an analysis of
thousands of different snapshots showed that the average reflectance of an
average photographic subject was about 18%. Therefore, when the camera
is looking at the reflected light from your subject, it will assume the subject
is reflecting back 18% of the light falling onto it, and infer what the
intensity of the original light source must be, and set the exposure for that

Contents of this book Copyright © 2014 Gary L. Friedman. All rights reserved.