Posterize Time Effect; Time Difference Effect - Adobe AFTER EFFECTS 7.0 Manual

ADOBE AFTER EFFECTS 7.0 541
User Guide
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Echo Operator: Composite in Front
Press the spacebar to preview the trail effect, use RAM Preview for a quicker preview, or render the composition
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to view the effect in real time.

Posterize Time effect

The Posterize Time effect locks a layer to a specific frame rate. It is useful on its own as a special effect, but it also has
more subtle uses. For example, 60-field-per-second video footage can be locked to 24 fps (and then field rendered at
60 fps) to give a film-like look. Also, nested compositions can be locked to a given frame rate. This effect is sometimes
called Strobe in hardware devices.
A layer's mask and any previously applied effects are ignored when the Posterize Time effect is applied. To posterize
the time of a masked layer, create the mask in another composition or precompose the layer with other effects before
applying the Posterize Time effect.
Animating the value of the Frame Rate slider can give unpredictable results. For this reason, the only interpolation
of the frame rate allowed is Hold.
This effect works with 8-bpc and 16-bpc color.
Posterize Time effect

Time Difference effect

The Time Difference effect calculates the color difference between two layers and is a useful aid in color correction;
use it to extract color differences when matching a clean background plate with foreground footage. It is also good
for creating mattes to be used to apply trails of smoke, fire, or echoing effects. Once you've applied Time Difference
to locate color differences in your footage, use color and levels controls to apply the color corrections.
This effect works with 8-bpc color.
Time Difference effect
Use Time Difference with Particle Playground to shed particles only from moving sections.
Adjust the following controls for the Time Difference effect:
Specifies the layer to be compared to the effect layer. The comparison layer's video does not need to be on
Target
(unless you select the source layer as the Target).