Step 4: Adjust The Midtones And Fine-Tune The Tonal Correction - Adobe PHOTOSHOP 5.0 User Manual

By default, the Auto feature clips the white and
black pixels by 0.5%—that is, it ignores the first
0.5% of either extreme when identifying the
lightest and darkest pixels in the image. This
clipping of color values ensures that white and
black values are based on representative rather
than extreme pixel values.
The Auto feature gives good results when an image
with an average distribution of pixel values needs
a simple contrast adjustment. However, adjusting
the Levels or Curves controls manually is more
precise. (See "Setting the highlights and shadows
using the Levels sliders" on page 117, and "Using
the Curves command" on page 120.)
To set the black and white points automatically:
1 Do one of the following:
Choose Image > Adjust > Auto Levels.
•
Open the Levels or Curves dialog box, as
•
described in "Using color adjustment commands"
on page 105, and then click Auto.
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 or
Curves 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.
Step 4: Adjust the midtones and
fine-tune the tonal correction
Once you have set the highlights and shadows, you
may want to fine-tune the contrast. This step is
usually not necessary with average-key images.
Setting the highlights and shadows typically redis-
tributes the midtone pixel values appropriately.
But when pixel values are concentrated on either
end of the grayscale, the midtones often need
adjustment.
You can use the gray eyedropper button in the
Levels or Curves dialog box to eliminate color casts
in the midtones. But for precise control over
midtone adjustments, use the Levels midtone
slider or Curves. (See "Setting the highlights and
shadows using target values" on page 114 for a
description of how the eyedropper buttons work.)
Adjusting the midtones using the Levels
sliders
The Levels sliders let you gradually adjust the
brightness, contrast, and midtones in an image. By
adjusting the midtones, you can change the
brightness values of the middle range of gray tones
without dramatically altering the shadows and
highlights.
To use the Levels sliders:
Open the Levels dialog box (see "Using color
1
adjustment commands" on page 105).
The Levels dialog box displays a histogram of the
image. (See "Step 2: Check the scan quality and
tonal range" on page 112.)
ADOBE PHOTOSHOP 5.0 119
User Guide