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Smart Blur: Adobe Photoshop noise & grain reduction filter.
Seldom-used tool works without adversely affecting image sharpness.
Below: ISO 1600 Nikon D1H action shot of a top fuel dragster at 300+ miles per hour during a nighttime qualifying session. A great picture, but look at the high ISO noise & grain, especially in the shadows.
What does Smart Blur do? It smoothes out grain and noise patterns
between edges without adversely affecting image sharpness or fine detail.
The Smart Blur filter is located in Adobe Photoshop's menu bar under Filter / Blur / Smart Blur...
The default values for the Smart Blur filter are Radius 3.0, Threshold 25.0, Quality Low, and Mode Normal.
I vary my Radius settings anywhere between 0.5 and 3.0, and seldom (if ever) go above or below this range. The live preview screen in the Smart Blur box shows the effect as you change the radius values to suit your taste for the picture at hand.
I rarely modify the default Threshold value, I've found that the default value of 25 seems to be perfect in most cases.
I use High Quality rather than the default Low setting. High Quality seems to produce a cleaner, smoother looking image.
And I leave the Mode set at Normal.
Below: After Smart Blur.
Image color, sharpness & important detail are retained, noise & grain are virtually eliminated.
Smart Blur can be really good for correcting ruddy, blotchy skin tones in high ISO pictures. Low radius values (0.5 to 0.8) will be necessary to retain natural looking skin textures.
If closeup fine detail appears degraded after applying the Smart Blur filter, lower threshold values to around 15 or so.
Smart Blur is not always the be-all, end-all, world's best noise reduction filter. But for some pictures, nothing works better and easier. It's simply another useful option.