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(what constitutes “high” varies with the image you’re working on). At lower values,
the improvement may be more subtle when compared to the “Better” mode, which
is less processor intensive than the computationally expensive “Enhanced” setting.
Additionally, “Enhanced” lets you decouple the Luma and Chroma threshold sliders
so you can add different amounts of noise reduction to each color component, as
the image requires.
Radius: Options include Large, Medium, and Small. A smaller radius offers greater real
time performance, and can provide good quality when using low Luma and Chroma
Threshold values. However, you may see more aliasing in regions of detail when using
low NR Threshold values.
Setting Radius to be progressively larger results in higher quality within areas of greater
visual detail at high Luma and Chroma Threshold values, at the expense of slower
performance. An NR Radius of Medium should provide suitable quality for most images
when using medium NR Threshold settings. As with many operations, there’s an
adjustable tradeoff between quality and speed.
Luma Threshold: Lets you determine how much or how little noise reduction to apply
to the luma component of the image. The range is 0–100, where 0 applies no noise
reduction at all, and 100 is the maximum amount. Too high a setting may eliminate fine
detail from the image.
Chroma Threshold: Lets you determine how much or how little noise reduction to apply
to the chroma component of the image by smoothing out regions of high-frequency
noise while attempting to preserve thesharpness of significant edge details. The range
is 0–100, where 0 applies no noise reduction at all, and 100 is the maximum amount.
Too high a setting may eliminate fine color detail from the image, although you may
find you can raise the Chroma Threshold higher than the Luma Threshold with less
noticeable artifacting.
Luma/Chroma Threshold ganging: Ordinarily, the Luma and Chroma Threshold
parameters are ganged together so that adjusting one adjusts both. However, you can
ungang these parameters in order to adjust different amounts of noise reduction to
each component of the image. For example, if an image softens too much at a certain
level of noise reduction, but you find there’s more color speckling than there is luma
noise, you can lower the Luma Threshold to preserve detail while raising the Chroma
Threshold to eliminate color noise.
NR Blend: Lets you dissolve between the image as it’s being affected by the Spatial
NR parameters (at 0.0) and the image with no noise reduction at all (100.0). This
parameter lets you easily split the difference when using aggressive spatial noise
reduction.
Using Noise Reduction
The following procedure suggests a method of using the Noise Reduction (NR) parameters to
achieve a controlled result.
Applying noise reduction to an image:
1 Enable Temporal NR by choosing 1 to 5 frames from the Number of Frames drop-down
menu. Keep in mind that more frames dramatically increase the render time of this effect,
while it may or may not significantly improve the result, depending on your material.
2 Choose options from the Motion Est. Type and Motion Range drop-down menus
corresponding to how much motion is in the image. If there’s a lot of motion, you
may need to choose Better and Large. If there’s not very much motion, lesser settings
may suffice.
Chapter – 134 The Motion Effects and Blur Palettes 2994