Reduce Noise in HDR Images with Photoshop Elements
Noise is problematic for high dynamic range (HDR) images. Although you can attempt to reduce noise in other parts of the HDR process, you have the most control over where, how, and how much to remove in post-tone mapping editing.
Noise reduction always poses a dilemma, however.
Too little: If you’re not firm enough, you’ll leave unwanted noise in your image, as in the image to the left in this figure.
Too much: If you’re too aggressive, you can destroy lines and detail in your images, resulting in something without sharpness — a soft image, as in the image to the right in this figure.
You can always apply noise reduction to the entire layer you’re working on. This is the massive retaliation option. It’s easy to do, too, which is a bonus.
Here’s how to apply noise reduction in Photoshop Elements:
Duplicate the layer you want to make the adjustment on.
You can’t duplicate the Background layer in Photoshop Elements if you haven’t converted the image to 8 Bits/Channel.
This figure illustrates a working noise reduction layer above the background. Apply noise reduction to this layer, and then duplicate it and continue working. You end up with a file with layers stacked on each other — each with a different adjustment.
Choose Filter→Noise→Reduce Noise to start the process.
In the Reduce Noise dialog box that opens, choose from
Strength (0-10): Determine how strongly you want to seek out and destroy noise. The catch is that Strength targets noise (the random, mottled specks of random pixels) that’s gray, black, or white — luminance noise.
Preserve Details (0-100%): Set how much you want to try to protect edge details in the image. This basically allows you to set a high Strength and have Elements remove noise in larger areas but not overdo it when it comes to lines and edges.
Reduce Color Noise (0-100%): Set this strength setting for noise that shows up in the image as variations in color.
Remove JPEG Artifact: If you see JPEG compression artifacts, selecting this check box tries to take them out. This shouldn’t be much of a problem for your HDR images.
Select OK to apply noise reduction.
Although you can use other methods for noise reduction in Photoshop Elements, Reduce Noise is the most applicable to HDR images because it works well to reduce noise without as much blurring, and happens to be more customizable than alternate methods. Try the other methods (accessible from the Filters→Noise menu), though, to see whether they work for you in certain circumstances:
Despeckle: This filter blurs everything except edges and produces a much softer image, which is fine in theory, or when you have a lot of speckles. You have no control over the strength, though, but you can blend. See the before and after in this figure.
Dust & Scratches: Don’t confuse this filter with removing sensor dust spots (which are normally much larger). It basically blends pixels together that contrast. Not a bad solution for actual dust and scratches on scanned prints, but even a light application renders a tone mapped image pretty blurry. See the before and after in this figure.
Median: The Median filter is sort of an averaging method that replaces pixels with the median value of pixels that surround them. This area can be large (resulting in a ton of blurring) or small (which still results in blurring, but not so much). See the before and after in this figure.