Correction
The correction special effects let you remove dust and scratch marks from images and sharpen images by increasing contrast, enhancing images edges, or reducing shading.
Dust and Scratch
The Dust and Scratch effect (Effects 
Correction Dust and Scratch) improves the appearance of an image that has small dust and scratch marks. The filter works by eliminating the contrast between pixels that exceed the contrast threshold you set. You can set a radius to determine how many pixels are affected by the changes. For more information, see Remove dust and scratch marks from bitmaps.
Tune Sharpen
The Tune Sharpen effect (Effects Correction Tune Sharpen) sharpens images by accentuating edge detail, focusing blurred areas, or increasing contrast. The filter lets you choose a percentage of sharpening to apply to the image and set a threshold of pixels changed by the effect. For more information, see Sharpen images.
You can also sharpen images by using individual Sharpen effects. For more information, see Sharpen.