Join Deke McClelland for an in-depth discussion in this video Reducing color noise, part of Photoshop CS5 One-on-One: Advanced.
- View Offline
The Reduce Noise Filter provides separate options for getting rid of Color Noise and luminance noise. So it's very possible, depending on the nature of your photograph, that you may be able to mitigate the noise across the entire photo in a single operation, just one pass of Reduce Noise and that's it. However, our noise problems are so endemic, we've got Color Noise across the entire image, we've got lots of luminance noise, mostly relegated to the shadows, we're going to have to take a two-tiered approach. So we're going to apply two passes of Reduce Noise, which don't overlap each other, as you'll see.
So everything is going to be hunky-dory. You may find that this two-tiered approach works for you as well. I'm still looking at Long feelers.jpg, found inside that 16_smooth folder, and I'm viewing the image at the 100% view size. Something I want you to notice is, just look at how big that noise is. Some of the noise details are just pretty ginormous. They really standout. They're every bit as big in terms of being mistaken for detail by a filter as these little hairs on this fellow's leg right there.
So in other words, we have some very fine details that we need to protect inside this image while getting rid of some pretty big problems. As you can see in this Final feelers. jpg image, we managed to do just that. So you can see that the noise is smoothed away like crazy in the background here and we still have every single one of those hairs intact in the foreground. In fact, they're stronger than ever. So you can see that they have been nicely sharpened, whereas they started life out, this way right here. All right! So how do we achieve such miraculous results? Well, the first thing I'm going to have you do is jump the image to protect the original.
So press Ctrl+Alt+J or Command+Option+J on the Mac in order to bring up the New layer dialog-box. Let's call this Color Noise, because we're going to get rid of the Color Noise on this layer. Click OK, and that's just a duplicate of the Background there. Now go up to the Filter menu, choose Noise, and choose Reduce Noise. Notice I've given you a keyboard shortcut, if you loaded dekeKeys, of Shift+F9. The Reduce Noise dialog box is a lot like Smart Sharpen, that is, it has the big whopping preview inside of it.
It also offers you the option of saving your settings. Now, it has the exact same drawbacks and features by the way as Smart Sharpen. So the preview has the same problems associated with it. When saving settings, you really have to be careful about how you approach it. So I'm going to suggest that we save every single modification as a new setting, because we do want to preserve our defaults right here, even though I have yet to ever apply these default settings to one of my photographs. I just actually don't find this particular group of settings to be very useful.
But let me explain what's going on here. Strength removes luminance noise. So this first guy, even though he's not called reduce luminance noise, he should be, because that's what he's doing. Notice when I hover over the option, it says Enter the strength for reducing luminance noise. That's totally what it does. Higher values are going to get rid of more noise. Lower values are going to get rid of less noise. Working against that option is Preserve Details. So Preserve Details is kind of a threshold function. Remember threshold from Unsharp Mask in the previous chapter.
Basically what its doing is it's finding neighboring pixels that are significantly different enough from each other in order to not smooth them over. So it protects pixels that are sufficiently different from each other from the Strength value. Higher values are going to protect more pixels. Lower values are going to protect fewer pixels. Next, we have Reduce Color Noise, which is going to get rid of the Color Noise inside the image. It's measured as a percentage. I'm not really sure why Strength is measured from 0 to 10 here and Reduce Noise is measured as a percentage, but that's the way it is.
Then we don't have anything to counteract Reduce Color Noise. We don't have a Color Details slider, instead we've got Sharpen Details, which takes the Preserve Details and then turns around and sharpens them, but you don't have a Radius value, and so you don't really have any control. So I'm going to make this pronouncement. In my opinion, if you want my recommendation, always shove this guy down to 0. I never use it. The reason is, because later you'll go back and apply your own custom sharpening, so why sharpen on top of previous sharpening, it just doesn't make sense, and in my experience it doesn't work well.
Finally, you have this Remove JPEG Artifact check box. If you're working with a heavily compressed JPEG image, for example, you found an image on the web and you are trying to work it into a composition and it's a public domain image, blah, blah, blah, why then, you may make the image look better by removing the JPEG compression artifacts. Don't expect it to completely get rid of the compression artifacts. That's fairly impossible. It's just going to work in a slightly different way. It's going to apply the Strength value in a different way, essentially in a more geometric pattern to match JPEG compression artifacts.
Anyway, that's not our problem in the case of this image. So here's what I recommend you do, because for starters here, we just want to attack the Color Noise. So let's take the Strength value down to 0, because we don't want to do anything to the luminance noise at this point. That gets rid of Preserve Details because there's nothing to preserve anymore. I already moved Sharpen Details down to 0%, as I always do. Then I'm going to start pumping up this Reduce Color Noise option. Let's check out what's happening here inside of the preview in the dialog box.
In fact, we may want to go ahead and zoom a little bit farther in, so that we can see that Color Noise in detail here. Now, remember, where these previews are concerned, when you click and hold, you see the before version of the image, and when you release, you see the actual preview. So when I click and hold, I can see the Color Noise, and I don't know if you can make it out, but it's there across that background, when I release, goes away, at least at 83%. I really have that value cranked high now. And now I'll scroll over to the inside of the insect's head.
Notice when I click and hold, I can see tons of colors inside that compound eye. When I release, the colors are much more uniform. We have some violets. We have some lower saturation colors here, some grays going on, little bit of blue information, but that's about it. Now, the thing you have to watch, it's very tempting to just max this value out and say, goodbye Color Noise, it's all out of there, but if you go that high, you're going to have a lot of colors bleeding into each other. So you're going to have these violets bleeding out of the eye into what should be neutral white areas.
Notice this color bleed that's happening at the top of the insect's eye, over here in its eyebrow. I don't know what that thing is. Anyway, I suggest we take this value down, to taste of course, but where this image was concerned, I decided I wanted it at about 70%. Now, before we go any farther, it's very important that we save off our settings, because otherwise we're going to wipe out the default settings. So I'll click on my trusty floppy disk. I'll call this guy Color noise 70%, let's say, and click OK.
Then of course, after I get done saving off the setting, that's not enough, I need to choose it from the Settings pop-up menu, like so, and then I'll go ahead and click the OK button in order to apply my modifications. Now, just for the sake of demonstration here, I'll go ahead and zoom in farther. This is the original color noisy version of the image. Check out the inside of the eye. Check out the background as well. This is the low Color noise version of the image, thanks to the specific application of a single value from the Reduce Noise dialog box.
Recommended prerequisite: Photoshop CS5 One-on-One: Fundamentals.
- Using blend modes, adjustment layers, and layer styles
- Organizing a layered composition so it is fluid and editable
- Creating and editing type in Photoshop
- Using blur effectively
- Using adjustment layers to add color
- Combining layers into a clipping mask
- Working with Camera Raw