The Sequence That Finishes Two Seconds Early
A 20-second title sequence is in trouble. The 3D department delivered 240 EXR frames at 1920x1080, rendered at 24 fps, with no metadata. The artist imported them with After Effects defaults and dropped the item into a 23.976 fps comp; the animation now finishes about two seconds early and the end of every shot sits on empty background. For review, the same artist rendered a 960x540 8-bpc H.264 file of the sequence and set it as a proxy. The producer then asked for the 1920x1080 master, and the delivered file was visibly soft. The editor also wants a version with a transparent background.
1. Explain the timing error with actual numbers and give the exact fix. Does changing the comp to 24 fps solve it?
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The math.
- Real duration: 240 frames / 24 fps = 10.0 seconds.
- After Effects assumes 30 fps for image sequences unless told otherwise: 240 / 30 = 8.0 seconds.
- Inside a 23.976 comp the item is therefore only 8 seconds long, so the animation ends 2 seconds early and the tail of the comp is empty. The frames themselves are also being sampled out of order in time, so the motion plays fast.
The fix is on the footage item, not the comp: Interpret Footage > Main > Assume This Frame Rate = 24. In a 23.976 comp the item then occupies its true 10 seconds, and After Effects resamples 24 fps source into the 23.976 comp grid with an occasional repeated or skipped source frame. That judder is normally invisible on titles; if it is not, retime deliberately with Time Remapping or a frame-blending effect rather than by fudging the assumed rate.
Changing the comp to 24 fps is the wrong lever. It changes every other layer's timing, the comp duration, and any audio sync, and it still leaves the footage item assuming 30 fps unless you also change the interpretation. Comp frame rate defines the sampling grid; footage frame rate defines how long the source really is. Confusing the two is what created the bug.
2. The master came out soft. Walk through the cause and the checks you run before re-rendering, and explain how the alpha version should be handled.
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Soft master. The proxy was still enabled. Setting a proxy points the footage item at a lower-resolution file for preview; it does not expire, and it is used at render time unless you turn it off. The comp panel's proxy indicator, or Layer > Use Proxies, is what you check, not the render settings. Adaptive Resolution and Fast Preview are preview-only and reset automatically at render, so they are not suspects here.
Checklist before re-rendering:
- Proxies off for the sequence, and the proxy assignment cleared if the file is finished with it.
- Output Module resolution at Full, not Half or Quarter.
- Output size matches 1920x1080, not a scaled-down comp.
- Bit depth of the render path is 16 or 32, not 8, since the source is EXR.
- Confirm you are rendering from the comp you think you are, not a review precomp.
Alpha version. The EXRs almost certainly carry alpha. Two things decide whether it composites cleanly:
- Interpret Footage > Alpha must match how the 3D department wrote the file. Premultiplied against black is typical; assuming Straight when it is not premultiplied produces dark fringes on every soft edge, and vice versa produces halos.
- The output module must be set to RGB + Alpha with a codec that supports it. A 4:2:2 codec cannot carry alpha at all, no matter what the channels dropdown says, so pick a codec that does, or use a PNG or EXR sequence. Also remove the comp background before the alpha render, or the delivered file will be fully opaque.