Adobe After Effects CS3 - Manual (Page 473)

AFTER EFFECTS CS3
User Guide
468
Original (left), and with effect applied (right)
Noise The type of noise. Uniform produces uniform noise. Squared creates high-contrast noise. Grain produces
grainlike noise similar to film grain.
Hue The amount of noise added to hue values.
Lightness The amount of noise added to lightness values.
Saturation The amount of noise added to saturation values.
Grain Size This control is active only for the Grain type of noise.
Noise Phase (Noise HLS only) An input value to the random number generator for the noise. When you set
keyframes for Noise Phase, the effect cycles through the phases to create animated noise. Greater value differences
between keyframes increase the speed of the noise animation.
Noise Animation Speed (Noise HLS Auto only) The speed of the noise animation. To accelerate or decelerate the
noise animation, animate this property.
Remove Grain effect
To remove grain or visual noise, use the Remove Grain effect. This effect uses sophisticated signal processing and
statistical estimation techniques in an attempt to restore the image to how it would look without the grain or noise.
While many techniques, such as applying a mild Gaussian Blur effect or the Median effect, reduce the visibility of
noise in an image, the tradeoff is an unavoidable loss of sharpness and highlights. The Remove Grain effect, in
contrast, differentiates fine image detail from grain and noise and preserves the image detail as much as possible.
The Remove Grain effect provides several options to precisely balance the reduction in noise and the amount of
sharpness retained in the image. Additionally, the Remove Grain effect can analyze the differences between frames
to further improve noise reduction and sharpness; since this process operates over time, it is called temporal filtering.
Note: Good degraining depends on good noise sampling. The results of the automatic sampling depend on the image
content and noise type. You can also change the number, size, and position of the samples to get the best results for a
particular image.
The Temporal Filtering controls of the Remove Grain effect use a statistical algorithm to blend the current frame
with previous and next frames. These controls are particularly effective in removing compression artifacts from DV
or video footage. Because temporal filtering works on the basis of differences between frames, it is useful only for
sequences.
To properly evaluate the results of this filter, the sequence must be viewed in real time, either with a RAM preview
or by viewing a movie rendered to a file.
To increase the speed of the Remove Grain effect preview, adjust the Remove Grain controls in order in the Effect
Controls panel. Specifically, the most efficient workflow is to find effective degraining settings first and to adjust the
last three controls last.
This effect works with 8-bpc and 16-bpc color.