Absolute Beginner's Guide to Digital Photography

Levels Dialog Box

The Levels dialog box in Photoshop and

Photoshop Elements is a subset of Curves. It isn’t

as powerful as Curves, but it is actually easier to

use. The reason is that the Levels feature

includes a visual representation of your image

called a histogram. A histogramis a visual graph

that shows the amount of pixels in an image

that use specific brightness values.

If you have an image open, examine its his-

togram by choosing Image, Adjustments, Levels.

In Photoshop Elements, choose Enhance,

Brightness/Contrast, Levels.

In 8-bit mode, an image can have 256 luminance values (or different brightness val-

ues) for each color. In other words, 256 shades of gray between pure black and pure

white are available for each pixel in each channel in a color image. A histogram

(see Figure 15.3) shows whether all 256 tones are being used (the x-axis of this

graph), and how many pixels in the image use a specific value (the y-axis).

CHAPTER 15 THE IMPORTANCE OF LEVELS AND CURVES 221

FIGURE 15.2
The result of
Auto Levels
occasionally
doesn’t produce
the desired
effect.

Before Auto Levels After Auto Levels

tip

You can also view a his-

togram of your image in

Photoshop by clicking Image,

Histogram. This view provides

significantly more informa-

tion on the tonal values in

an image, but the informa-

tion isn’t really valuable unless you

plan to use Curves.

FIGURE 15.3
A histogram.
The x-axis
shows 256 gray
(brightness) val-
ues; the y-axis
shows the
amount of pix-
els with each
gray value.

Black 50% Gray White

Number of pixels

0255 256 Brightness Values