Apple Aperture 2 - Manual (Page 362)

362 Part III Performing Image Adjustments
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.
Likewise, histograms can also depict lack of contrast in an image. For example, an
image of a rainbow in the fog lacks contrast. Without directional lighting, there aren’t
any highlights or shadows in the image. In this case, the peaks of the histogram are
concentrated in the center and do not come close to either the dark or bright sides.