Sometimes you need (or simply want) more control than what’s offered by
the Auto commands. You might have a more demanding problem or a more
expansive artistic vision. You might need to make major corrections orcreate stupendous effects. Photoshop, not surprisingly, offers that sort of
control over your image. In fact (and also not surprisingly), you have several
ways at your disposal to manipulate the tonality of your images. Two of the
most commonly used are Levels and Curves, both found in the Adjustments
panel and the Image➪Adjustments menu.
The Image➪Adjustments➪Levels command (Ô+L/Ctrl+L), or adding a Levels
adjustment layer (discussed in Chapter 8), gives you control over shadows,
highlights, and your image’s overall tonality individually. Using a slider with
three controls, you adjust the picture both to suit your eye, and with an eye
on a histogram for reference. You even have numeric fields in which you can
type exact values, should you find the need.To perform the basic Levels correction, spreading the image’s tonality over
the full range of values available, you simply drag the slider controls under the
histogram in the Levels dialog box inward until they’re under the point where
the histogram begins to rise in a mountain shape. Ignore those little flat tails
that extend outward — they represent individual stray pixels — and drag the
little pointers under columns that are at least a few pixels tall. The histogram
in the Levels dialog box (as shown in Figure 5-9) is for reference as you make
changes. Note, however, that while you work in Levels, the Histogram panel
updates, showing you the “after” in black, with the “before” histogram in color.
The Levels dialog box (and the Curves dialog box, too) offers another way to
make tonal corrections to your image — sort of a half-automated technique,
using the three eyedroppers in the right side of the dialog box. Open your
image, open the Levels dialog box, and correct both tonality and color in
your image with three little clicks:
1. Click the left eyedropper on something that should be black.
This might be a shadow, a piece of clothing, or the tire of a car.
Generally, you click something in the image that’s already quite dark.
2. Click the right eyedropper on something that should be white.
A cloud, the bride’s dress, perhaps an eye . . . all are likely targets for the
highlight eyedropper. You usually click something that’s already quite light.
3. Click the middle eyedropper on something that should be gray.
Click something that should be neutral in color (should be, not already
is). It doesn’t have to be mid gray, just something that should be neutral.
This reduces or eliminates any unwanted color cast in the image. If you
don’t like the result, click somewhere else in the image. Keep clicking
until the colors in the image look right.
One step up from Levels in complexity, and about five steps ahead in terms
of image control, is Image➪Adjustments➪Curves (Ô+M/Ctrl+M). The Curves
dialog box has a pair of slider controls (similar to the left and right sliders
in Levels) to easily control the endpoints of your shadows and highlights.
The curve line itself gives you control over various parts of the tonal range
independently. Curves also offers eyedroppers for tonal and color correction.
They’re used the same way you use the eyedroppers in Levels.
