Scripts and expressions for working with text – Adobe After Effects CS4 User Manual
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USING AFTER EFFECTS CS4
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Last updated 12/21/2009
Best practices for creating text and vector graphics for video
Text that looks good on your computer screen as you are creating it can sometimes look bad when viewed in a final
output movie. These differences can arise from the device used to view the movie or from the compression scheme
used to encode the movie. The same is true for other vector graphics, such as shapes in shape layers. In fact, the same
problems can occur in raster images, but the small and sharp details of vector graphics cause the problems most often.
Keep in mind the following as you create and animate text and vector graphics for video:
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You should always preview your movie on the same kind of device that your audience will use to view it, such as an
NTSC video monitor. (See “
Preview on an external video monitor
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Avoid sharp color transitions, especially from one highly saturated color to its complementary color. Sharp color
transitions are difficult for many compression schemes—such as the compression schemes in MPEG and JPEG
standards—to encode. These compression schemes can cause visual noise near sharp transitions. For analog
television, the same sharp transitions can cause spikes outside the allowed range for the signal, also causing noise.
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When text will be over moving images, make sure that the text has a contrasting border (such as a glow or a stroke)
so that the text is still readable when something the same color as the fill passes behind the text.
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Avoid thin horizontal elements, which can vanish from the frame if they happen to be on an even scan line during
an odd field, or vice versa. The height of the horizontal bar in a capital H, for example, should be three pixels or
greater. You can thicken horizontal elements by increasing font size, using a bold (or faux bold) style, or applying
a stroke. (See “
Formatting characters and the Character panel
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When animating text to move vertically—for scrolling credits, for example—move the text vertically at a rate in
pixels per second that is an even multiple of the field rate for the interlaced video format. Such a rate of movement
prevents a kind of twitter that can come from the text movement being out of phase with the scan lines. For NTSC,
good values include 0, 119.88, and 239.76 pixels per second; for PAL, good values include 0, 100, and 200 pixels per
second.
Apply the Autoscroll - Vertical animation preset in the Behaviors category to quickly create a vertical text crawl
(for example, a credit roll).
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To avoid the risk of twitter that comes with vertical motion, thin graphical elements, and fields, consider presenting
credits as a sequence of blocks of text separated by transitions, such as opacity fades.
Fortunately, many problems with text in video and compressed movie formats can be solved with one simple
technique: Apply a blur to the text layer. A slight blur can soften color transitions and cause thin horizontal elements
to expand. The Reduce Interlace Flicker effect works best for the purpose of reducing twitter; it applies a vertical
directional blur but doesn't blur horizontally, so it degrades the image less than other blurs.
More Help topics
Apply an effect or animation preset
Scripts and expressions for working with text
based on the contents of a text file. You can either create one text layer from all of the text, or you can create one layer
for each line in the text file. The script also provides options for leading and other spacing.
that demonstrates the text formatting features
available through the scripting interface.