How to Reduce Noise in Images in Photoshop CS6
Although the Add Noise filter in Photoshop CS6 adds grain, the other filters in the Noise submenu don’t add noise at all; instead, they make noise and artifacts (flaws, such as the dust and scratches on old film) less noticeable. Choose Filter→Noise to find your tools, which include:
Despeckle: This filter makes dust spots in your image less noticeable by decreasing the contrast of your entire image — except at the edges. That translates into a slightly blurry image (which masks the spots) that still retains sharpness along the edges of image components. You end up with a little blur to soften the image but enough detail in the edges that the picture still looks good.
Dust & Scratches: This filter concentrates its blurring effect on only those areas of your image that contain scratches and other artifacts. Photoshop performs this magic by looking at each pixel in an image and moving out in a radial direction until it encounters an abrupt transition in tone. (That’s a signal that a spot or scratch has been found.)
You can specify the radius in which Photoshop searches for the little culprits, from 1 to 100 pixels. Be careful not to overdo it. Too much of this filter can obliterate the detail in the image. Leave the Threshold at 0. If you journey into the world of mush, try using Edit→Fade right after you apply the filter.
When working with any of the Noise filters, be very conservative at first. All the Noise filters involve destruction of image data. Remember, that’s just the nature of filters, in general — changing pixel data. A little bit can help — and be just the effect you’re looking for. Just a little bit more, however, may completely wreck things.
Median: This filter reduces contrast around dust motes, thus hiding them, in a slightly different way. This filter looks at the pixels surrounding each pixel in the image and replaces the center one with a new pixel that has the median brightness level of that group. Basically, the bright spots darken while the rest of the image isn’t affected.
Reduce Noise: This filter is designed to remove luminance noise and JPEG artifacts that can appear on digital photos. Luminance noise is grayscale noise that makes images look overly grainy. Here’s some info on the options:
Strength: Specify the amount of noise reduction. You can reduce noise in the overall image or (if you click the Advanced button) channel by channel.
Be sure to check out the Blue channel, in particular. It’s often the channel that captures all the crud.
Preserve Details: A higher number preserves edges and details but reduces the amount of noise removal. Find a happy medium.
Reduce Color Noise: Removes random colored pixel artifacts.
Sharpen Details: Counteracts the fact that removing noise reduces sharpness, as well.
Remove JPEG Artifact: Check this option to remove the annoying blocks and halos that can occur because of low-quality JPEG compression.
You can also save and reload your settings. Click the disk/arrow icon. In the New Filter Settings dialog box, enter a name for your settings and click OK. To load your settings, choose your desired settings from the Settings drop-down menu (pop-up menu on the Mac).