It’s inevitable when you’re making digital photographs that you are going to encounter digital noise. Noise in an image is the result of variability in the light level readings from one sensor pixel to the next. Even the best quality sensors will produce some level of noise, and the noise will be amplified under certain conditions. Fortunately, with Lightroom, we have built-in noise reduction capability, and the performance is exceptionally good.
In general, the two most likely circumstances that will produce noise in your images are:
- High ISO settings
- Long exposures
Both of these factors tend to come into play most often in low light photography. What does the noise look like? It has two distinct and different forms, and each can be addressed individually. The two types of noise that you’ll encounter in your image are luminance noise, and color noise. Luminance noise tends to resemble grain, but may be overpowering depending on the image and the settings. Color noise, on the other hand, tends to take on the form of magenta and green splotches in the image, especially in the shadows of an image. Here’s an example of both types of noise:
These types of noise can occur in other situations, as well. In the case of the image below, I photographed this lovely Rose of Sharon flower in the rain – but I had just been photographing indoors under low natural light, and my ISO was set to 3200 – and I forgot to change it back. The image doesn’t look too bad at this size:
However, if we look more closely, we can see a high level of noise. Here is the same image zoomed to 100%:
We can take care of this with Lightroom, and relatively quickly. In the Develop module, we can open the Detail section, and here is where we find sharpening and noise reduction. We’re going to focus on noise reduction in this tutorial.
In order to see the results of noise reduction and sharpening, we want to view our image at 100%, Anything less, and we won’t see the effect.
As we can see, there is already some color noise reduction being applied in this image (the default value in Lightroom is 25%). If we set the color noise reduction to 0, we can see the full extent of noise in this image. We have a lot of color noise, as evidenced by the magenta and green splotches, in addition to the luminance noise. In this image, I’ve zoomed to 3:1 (300%) so that you can really see the color noise:
Lightroom by default applies a color noise reduction of 25, and this is often enough to remove the typical color noise that you’ll find in your images. Noise reduction will soften the image, though, so we may not always want this default. You’ll need to experiment with your own images to see what works. For this image, we can use a value of 15%, and that works well.
But what about the luminance noise? We can adjust the luminance noise reduction to compensate for this type of noise. Just drag the slider while viewing the image, and we can see a remarkable difference as the value is increased.
Again, remember that you must view the image at least at 100% to see this effect. We’re at 300%, but here it is at 100% as well:
Notice as we increase the noise reduction, the image details are slightly blurred. This is a side effect of noise reduction, and we have an ongoing tradeoff between sharpness and noise as we develop our images.
We can restore some of the sharpness by increasing the sharpness setting, but pushing it too far will end up sharpening the noise. There are a couple of settings under luminance noise that can help us a bit, though.
The first is Detail, and you can think of this as a “threshold” slider. Adjust it all the way to the left, and all detail is treated as noise, and softened. All the way to the right, and only larger details are considered noise. The default of 50 works well in most cases, but you’re free to experiment with it.
The second setting is often more useful – Contrast. This setting can be used to introduce a little extra edge contrast that may have been lost in the softening effect of the noise reduction. Again experimentation is key, and no two images are likely to behave exactly the same way. Keep in mind, as with sharpening, adding more contrast can bring back some of the noise you’re trying to reduce.
Color noise reduction has some settings, as well. The first slider is detail. This is a threshold adjustment similar to the one for luminance noise. Turning this one all the way up tries to maintain some color detail, and we might end up with some color artifacts remaining. Here is a view at 300% to show the effect:
The other control for color noise reduction is new in Lightroom 5, and it is color smoothing. This control can help with any remaining color artifacts, by smoothing the low frequency color aberrations. By default it is set to 50%, but feel free to push it if you have some stubborn color noise splotches, and see if it doesn’t help minimize them further.
At the end of the day, noise reduction is a judgment call. It’s up to you, and the amount of noise you remove or keep will define your style. Keep in mind that when you print, some noise will be softened in the printing process as well – so don’t be afraid to leave some noise present.
Finally, I’ll leave you with a comparison of Lightroom with some of the more popular noise reduction dedicated solutions. I’ve found that Lightroom can hold its own pretty well, and I’m rarely driven to make much use of the dedicated solutions for my raw conversions.
Here’s the final image from Lightroom 5:
Here is the same image noise reduced in Google’s Nik Dfine 2:
And here it is with Topaz DeNoise 5:
Here is the finished image with Imagenomic Noiseware 5:
As you can see here, Lightroom does as well as any of the third party dedicated solutions, at least with this image. As a disclaimer, I’m not an expert with DFine, so I may not have been able to coax the best results from that software. For the others, I saw subtle differences, but I thought Lightroom’s results were as good, and didn’t require a separate editing session to implement.
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