Despeckle, Dust & Scratches, Median and Reduce Noise are all tools that are built into Photoshop, and they may be the only tools you need
By John Paul Caponigro
Noise Filters In Photoshop
Despeckle, Dust & Scratches, Median and Reduce Noise. They’re all useful tools for modest amounts of noise. They may be all you need for an extra pass of noise reduction after RAW conversion. Build yourself a safety net when using these filters. Don’t apply them to the Background layer. Apply them to a duplicate of the Background layer. Then you’ll be able to redo noise reduction at anytime in the future. Noise reduction tools surely will improve as time passes. You’ll also be able to mask the effect to affect only selected portions of an image, use Layer Styles Blend If sliders to restrict an effect to shadows, midtones or highlights, and use Blend Modes to target luminosity, hue or saturation. A deeper look at these four filters will benefit every Photoshop user.
Median Dialog Box
Despeckle. It’s a bare-bones simple filter. There’s one strength and one setting. There’s no dialog box. You can apply it multiple times for stronger applications. You can apply it to individual channels (i.e., if the blue channel has more noise than the others) or selectively (to low-frequency smooth areas) to make it more targeted. That’s it. It’s that simple. How well does it work? Well enough so that it’s a good idea to become familiar with it. It does a reasonable job for modest amounts of noise. It never performs miracles. But it can be a final touch worth applying to many images. It’s also useful for reducing noise in masks and effects layers.
Median. It’s simple. There’s only one slider, Radius. Radius controls the amount of blurring. The blurring Median provides is substantially more aggressive than Despeckle. Only very low settings are useful for photorealistic images. Be very careful with this filter. With even modest applications, it can subdue important textural detail. With moderate applications, it can even smooth and reshape contours. Apply it aggressively to see just how far it can go. You’ll see it quickly goes too far.