Absolute Beginner's Guide to Digital Photography

CHAPTER 15 THE IMPORTANCE OF LEVELS AND CURVES 223

FIGURE 15.6
This histogram,
with most of its
pixels closer to
white, is either
an outdoor shot
on a brightly lit,
overcast day, or
a mistake cour-
tesy of excessive
flash.

The bottom line is that each image you open has a different distribution of tonal

values. The graph shows how many pixels contain a specific brightness value. Dark

images will always have most of their pixels on the left side of the histogram. Bright

or light images will have the majority of their pixels at the far right end. Images

with excessive gray values will have a pixel distribution in the center of the his-

togram. The goal is to have pixels represented at each point on the x-axis of the his-

togram.

Fixing an Image

To fix images with awkward histograms, use the slider triangles under the histogram

to change the distribution of tonal values in the image. Follow these steps to fix a

sample image:

1. Open an image that needs correction and save it with a new name.


2. Select Image, Adjustments, Levels. The Levels dialog box will appear.


3. Look at the histogram for your image. If the graph looks balanced with pixels
   at every tonal value, you might not need to do anything. If the black triangle
   is to the far left of the graph, slide it to the right until it is under the start of
   the histogram. If the white triangle is to the far right of the graph, slide it to
   the left until it is under the start of the histogram.


4. Click Preview to view the change to your image. The image should appear
   brighter, with more contrast, and generally more appealing.


5. If the change is not what you wanted, click Cancel or press and hold down
   the Alt key and click Reset (the Cancel button changes to Reset when you
   press and hold down Alt). On the Mac, press xto see the Reset button.