Adobe Photoshop CS4 - Manual (Page 185)

178 USING PHOTOSHOP CS4
Color and tonal adjustments
Last updated 1/10/2010
Black Clip And White Clip Specifies how greatly the shadows and highlights are clipped to the new extreme shadow
(level 0) and highlight (level 255) colors in the image. Larger values produce an image with greater contrast. Be careful
not to make the clipping values too large, because doing so reduces detail in the shadows or highlights (the intensity
values are clipped and rendered as pure black or pure white).
Add contrast to a photo
You can add contrast to an image in two ways, depending on the problem.
If the image needs overall contrast because it doesn’t use the full tonal range, click the Levels icon in the
Adjustments panel. Then drag the Shadow and Highlight input sliders inward until they touch the ends of the
histogram.
image layer don’t extend to the ends of the graph, indicating that the image is not using the full tonal range.
A. Shadow Input slider B. Highlight Input slider
If the image uses the full tonal range, but needs midtone contrast, Click the Curves icon in the Adjustments panel.
Drag the curve into an S shape.
Increasing the slope in the middle of the curve increases contrast in the midtones.
More Help topics
“ About adjustment and fill layers ” on page 311
Adjust Exposure for HDR images
The Exposure adjustment is designed for making tonal adjustments to HDR images, but it works with 8-bit and 16-bit
images. Exposure works by performing calculations in a linear color space (gamma 1.0) rather than the current color
space.
1 Do one of the following:
• Click the Exposure icon or an Exposure preset in the Adjustments panel.
• Choose Layer > New Adjustment Layer > Exposure.
Note: You can also choose Image > Adjustments > Exposure. But keep in mind that this method makes direct adjustments
to the image layer and discards image information. Adjustment layers for 32-bit images are available in Photoshop
Extended only.
A B