Nikon D7000 manual 131

Chapter 4 ■ Getting the Right Exposure 131

In working with histograms, your goal should be to have all the tones in an image spread out between the edges, with none clipped off at the left and right sides. Underexposing (to preserve highlights) should be done only as a last resort, because retrieving the under- exposed shadows in your image editor will frequently increase the noise, even if you’re working with RAW files. A better course of action is to expose for the highlights, but, when the subject matter makes it practical, fill in the shadows with additional light, using reflectors, fill flash, or other techniques rather than allowing them to be seriously underexposed.

The more you work with histograms, the more useful they become. One of the first things that histogram veterans notice is that it’s possible to overexpose one channel even if the overall exposure appears to be correct. For example, flower photographers soon discover that it’s really, really difficult to get a good picture of a rose, like the one shown in Figure 4.23. The exposure looks okay—but there’s no detail in the rose’s petals. Looking at the histogram (see Figure 4.24) shows why: the red channel is blown out. If you look at the red histogram, there’s a peak at the right edge that indicates that high- light information has been lost. In fact, the green channel has been blown, too, and so the green parts of the flower also lack detail. Only the blue channel’s histogram is entirely contained within the boundaries of the chart, and, on first glance, the white luminance histogram at top of the column of graphs seems fairly normal.

Any of the primary channels, red, green, or blue, can blow out all by themselves, although bright reds seem to be the most common problem area. More difficult to diag- nose are overexposed tones in one of the “in-between” hues on the color wheel.

Figure 4.23

It’s common to lose detail in bright red flow- ers because the red channel becomes over- exposed even when the other channels are properly exposed.