Apple Aperture 3.5 - Manual (Page 346)

Chapter 7 Make image adjustments 346
About evaluating tonality and contrast
Although histogram graphs are good tools for evaluating an image’s exposure, you shouldn’t
interpret histograms for exposure information only, because the shape of the histogram is also
influenced by the tonality in the scene. You need to take the subject of the image into account
when evaluating its histogram. For example, images shot at night naturally have a majority of
peaks in the darker side of the histogram.
Likewise, images of bright scenes, such as snow or light reflecting off the ocean, have a majority
of their peaks in the brighter side of the histogram.
Histograms can also depict contrast in an image. For example, this silhouette of the man in the
hammock in front of the sunset consists of a relatively even assortment of extreme bright and
dark tonal values with few midtones. In this case, the histogram is shaped like a valley with peaks
in both the dark and bright sides.
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