Adobe PHOTOSHOP ELEMENTS Manual page 94

CHAPTER 4
86
Making Color and Tonal Corrections
Using the Auto Levels command
The Auto Levels command defines the lightest and
darkest pixels in an image, and then redistributes
intermediate pixel values proportionately. Because
Auto Levels adjusts each color channel (red, green,
and blue) individually, it may remove or introduce
color casts.
Auto Levels gives good results when an image with
an average distribution of pixel values needs a
simple contrast adjustment.
To use the Auto Levels command:
Do one of the following:
• Choose Enhance > Auto Levels.
Open the Levels dialog box. (See "Using the
•
Levels dialog box" on page 87.) Then, click Auto,
and click OK.
To change the amount of white and black values
clipped:
Hold down Alt (Windows) or Option
1
(Mac OS), and click Options in the Levels
dialog box.
In the Auto Range dialog box, enter the
2
percentage of extreme highlight and shadow pixels
to ignore, and click OK. A value between 0.5% and
1% is recommended.
Using the Auto Contrast command
The Auto Contrast command adjusts the overall
contrast and mixture of colors in an image
automatically. Because it does not adjust each
color channel (red, green, and blue) individually,
Auto Contrast does not introduce or remove color
casts. It maps the lightest and darkest pixels in the
image to white and black, which makes highlights
appear lighter and shadows appear darker.
Auto Contrast can improve the appearance of
many photographic or continuous-tone images.
It does not improve flat-color images.
To use the Auto Contrast command:
Choose Enhance > Auto Contrast.
Using the Adjust Backlighting command
When taking pictures, you can use backlighting to
emphasize the shape of the subject and bring out
details in the background of a digital photo or
image. However, backlighting can cause underex-
posure in the subject of a picture. You can use the
Adjust Backlighting command to correct this
problem.
Original image, and Backlighting applied