Adjusting images 195
The Histogram Stretch command pulls the darkest pixel down
to black and the lightest pixel up to white. This command does
not affect images that already span from pure black to pure
white. If the original image has pixels that are very close to black
and white, using this command will have a very small effect. If
the original image is very flat (nothing close to black or white),
using this command will have a strong effect.
To adjust brightness, contrast, and gamma simultaneously
Edit workspace
1 Choose Adjust Brightness and Contrast Levels.
The Levels dialog box appears.
2In the Levels group box, choose the color channel to adjust from
the Channel drop-list:
• RGB — lets you edit the red, green, and blue channels in a
combined histogram
• Red — lets you edit the red channel only
• Green — lets you edit the green channel only
• Blue — lets you edit the blue channel only
3 Adjust the black, gray, or white diamond sliders, or set values in
the controls beneath them.
• To darken the darkest pixels in the photo, drag the black
diamond slider to the right (or set a value in the numeric
control).
• To adjust the photo’s midtones, drag the gray (middle) diamond
to the left or right (or set a value in the numeric control).
• To lighten the lightest pixels in the photo, drag the white
diamond slider to the left (or set a value in the numeric control).
Note: To see which pixels are being clipped as you drag either the
black or white diamond slider, hold down Ctrl as you drag. The
After pane displays the clipped colors.
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