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Try Applying Temporal NR First, then Applying Spatial NR
Because Temporal NR analyzes multiple frames for its noise isolation, it tends to be better at
preserving detail accurately in regions of the image where there’s little motion. If you try applying
Temporal NR first and get a successful result, even if only in part of the image, you may reduce how
much Spatial NR you have to apply, thus improving the overall quality of your final result.
Keep in mind that while Temporal NR does a great job in unmoving parts of an image but is less
effective when dealing with subjects in motion, Spatial NR is able to reduce noise everywhere in the
frame falling below its threshold, even when there’s motion. Ultimately, a combination of the two is
almost always going to be a winning combination.
Spatial NR Radius, How Large Should You Go?
Larger NR Radius settings can dramatically improve the quality of high-detail regions in shots where
you’re using aggressive Spatial noise reduction, but it’s not necessary to always jump to the large
Radius setting, which provides the highest precision. In many cases, when evaluating an image that
you’re applying noise reduction to, you may not actually be able to perceive the additional quality, and
you’ll waste processing time on an unnecessary level of correction.
It’s a good idea to make sure that you’re evaluating the full-frame image on a large enough display to
see the noise you’re working on within the viewing context of the intended audience. Zooming really
far into a clip while applying noise reduction may encourage you to use higher quality settings than
are necessary, because an excessively enlarged detail of an image lets you see subtle changes that
you wouldn’t notice at actual size.
Limiting Noise Reduction in Useful Ways
As with any other correction in the Color page, noise reduction can be limited using HSL Qualification
or Power Windows. This means you can focus your efforts on reducing noise in the most problematic
areas of an image (for example, in shadows and background regions), while sparing elements that you
don’t want to affect (such as faces or better-lit areas of the image).
Furthermore, you can use Spatial NR in lieu of Blur operations to perform a subtler form of complexion
smoothing, using the HSL qualifier or a window to isolate an actor’s skin tone for targeted
noise reduction.
Controlling the Order of Operations for Noise Reduction
You can apply noise reduction at any point in your image processing tree using a dedicated node. If
you have an image with noise that you think might be enhanced by whatever corrections you need to
make (increasing the contrast of underexposed clips often increases whatever noise is within an
image), there are two approaches to noise reduction:
– Apply noise reduction at the beginning of a node tree: This lets you pre-emptively eliminate
any noise before it becomes a problem as a result of whatever adjustments you’re planning to
make. The result can be smoother, but you may also notice that the edge detail within the image
is a bit softer.
– Apply noise reduction at the end of a node tree: The alternative is to make your adjustments first,
and then apply noise reduction in a separate node afterwards. In this case, you may find that the
noise reduced regions of the image aren’t quite as smooth, however the edge detail within the
image may be visibly sharper as a result.
– Apply noise reduction to only one color channel of an image: Using the Splitter/Combiner nodes,
you can also apply noise reduction to only one color component of an image. If you’re grading a
video clip with a noisy Blue channel, this can be a way to focus noise reduction where it’s needed.
Isolating a single color channel for noise reduction is also possible using the Channels selection
when right-clicking a node. By selecting the specific channel numbers in this node corresponding
to your color space (RGB, YUV, LAB, etc.), you can limit the noise reduction operation to the
appropriate channels only.
Chapter 150The Motion Effects and Blur Palettes 2981
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