Shake Reduction Concepts and Controls
As mentioned earlier, the Blur Estimation Region shows where Photoshop CC examines pixels and tries to determine how much camera shake or blur is present in that area. However, the Shake Reduction filter's final correction will affect the whole image. Ideally, the default region should include details that are supposed to be in focus, based on your camera settings. Each area also should contrast strongly with its background in terms of tones or color.
The estimation region is important, but the Blur Trace Settings in the upper-right quadrant of the window determine how the blur is corrected and to what degree (see Figure 8).
What exactly is a blur trace? Illustrated by the small black square(s) in the Advanced section of the settings area, the blur trace is analogous to a miniature mask that Photoshop generates as a means of defining the "shape" of the blur. Often the shape of the trace covers only a few pixels. With more severe blurring, it will look more like a streak or smudge.
Figure 8 The Blur Trace settings (top) define how the filter corrections are made, and the blur trace (black square) indicates the shape of the blur.
In the Blur Trace Settings section of the window, the following options are available:
- Blur Trace Bounds. Described as "the maximum bounds of the selected blur trace, in pixel units," this is essentially the "span" of the blur, as estimated by Photoshop on its first pass. If the surface texture of your subject(s) looks accurate, but the edges are a little jagged or showing halos, reduce this value a few points at a time until the edges have a more natural look.
- Source Noise. Typically, leaving this option set to Auto produces a good result; its main purpose is to mitigate any grainy pixels or noise that's amplified by the sharpening effect. If you have a darker or higher ISO shot, you may want to boost this setting to Medium or High and see whether you notice a difference from the Auto setting. Having this feature is one reason why you don't need to apply extra noise reduction in ACR.
- Smoothing. This feature helps to smooth over-corrected pixels that end up creating grainy-looking areas; it does this while leaving the edge contrast improvements intact.
- Artifact Suppression. If you see really pronounced halos, edge duplication (ghosting), and other artifacts around your sharpened edges, boosting the Artifact Suppression setting will help to remove them substantially, if not completely.