Adobe AFTER EFFECTS 5.5 Help Manual page 368

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4 For each of the Map Red To, Map Green To, and Map Blue To option groups, choose a
property from the menu to associate it with the color channel as necessary. You don't have
to map properties to all of the color channels. For example, if you want to change scale
over an image map, you can map the color red to scale without setting other properties.
5 If necessary, for each Map To option group, specify the lowest and highest values you
want the layer map to produce using the Mix and Max options. Min is the value to which a
black pixel will be mapped, and Max is the value to which a white pixel will be mapped.
The complete tonal distribution between Min and Max is then scaled proportionally. See
"Using Min and Max options to adjust the output range of a layer map (PB only)" on
page 368.
6 If you're using the Ephemeral Property Mapper, you can also choose an operator to
apply to the value of a particle property and the value of the corresponding layer map
pixel. For more information, see "Using Ephemeral Property Mapper operators to adjust
values (PB only)" on page 369.
Note: Because particle properties use many kinds of units, such as pixels, degrees, and
seconds, you may want to compress or expand the range of values from the layer map so
that all the resulting values are usable in the measurement system of a specific particle
property. First, use the Min and Max options, which define the range of values to use from
the layer map. If further adjustment is necessary and you're using the Ephemeral Property
Mapper, use mathematical operators that can amplify, attenuate, or limit the effect of a
layer map.
Using Min and Max options to adjust the output range of a layer
map (PB only)
When the overall range of layer map brightness values is too wide or narrow, use the Min
and Max options to stretch, compress, or shift the range of values produced by the layer
map. The following examples describe when you might want to adjust Min and Max:
You want to set the smallest font size for your text to be 10 points and the largest size to
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be 96 points. Set the Min value to 10 and the Max value to 96.
You set the initial color of a particle and then use a layer map to change particle colors.
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If you find that the color changes aren't dramatic enough, you can lower the Min value
and raise the Max value to increase the contrast of the color changes.
You set the initial velocity of a particle and then use a layer map to affect the X Speed
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property. However, you find that the difference between the fastest and slowest
particles is too great. By raising the Min value and lowering the Max value for the layer
map channel that is mapped to the X Speed property, you narrow the resulting range
of particle speeds.
You use a layer map to affect the Scale property of particles and find that the smallest
•
particles aren't small enough while the largest resulting particles are too large. In this
case the entire output range needs to be shifted down; lower both the Min and
Max values.
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