Graphics Programs Reference
In-Depth Information
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Now, use the Zoom tool to zoom into the leafy area of the image. Note that he values are now chopped
up into 16 levels. You essentially have destroyed the nice tonal gradation from one color to another.
Tonal values before posterizing.
Change levels to 16.
Image after posterizing.
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Take a look at your Histogram panel. If necessary, click the alert triangle symbol in the upper-right
section of the panel to refresh the reading. Notice that the Histogram reflects the changes you have
made by showing the tonal values spread out across all values with large spaces in-between.
The Histogram displays the poor tonal values in this image.
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Choose File > Close, do not save changes.
You must understand that this elimination of the levels in the Histogram occurs when you make any
changes to your tonal values in Photoshop. If you use Levels, then Brightness and Contrast, and then
Curves, you remove important tonal information. This is why you will learn to correct color values,
brightness, and contrast with the Curves panel, since it has the capability to correct all three with the min-
imal amount of tonal damage.
What images need to be color corrected?
Generally, images that need color correction are images that include a neutral (gray tonal values) or in-
clude skin tone. A neutral is essentially anything in the image that is gray: a shade of gray or light to dark
grays. A gray value is composed of equal amounts of red, green, and blue.
The fact that gray is created from equal amounts of RGB makes it easy for viewers to notice when colors
are “off”. If you have an image of an orange sunset, viewers are less likely to know whether the color is
accurate. A color cast could be intentional for mood, and viewers would have no reference for the origin-
al scene. On the other hand, if someone is wearing a dark suit and tie in an image, and the shirt is slightly
pink, the slight pinkish color cast would be more noticeable.
In our example below, the left image is not corrected. The whites and grays in the image might look dirty
or as though they have a color cast over them. The image on the right has had the grays neutralized using
curves, which you will learn to do in this lesson.
