Glow

Amount is the energy dial. The working zone is narrower than the slider suggests: Amount 10–60 reads as photographic bloom, 100–300 reads as heavy sci-fi, and past ~400 (the hard range runs far beyond the slider) you’re deliberately flooding the frame. The default of 25 is a visible but restrained halation.

Size sets the falloff footprint in pixels — roughly a doubling feel per +100. Keep Size 25–60 for a tight halo that hugs its source; Size 100–200 turns sources into large soft ambience. Falloff then trades hot-core against far-field energy along that footprint: low values concentrate the bloom at the source, high values push more of it into the distant tail.

Highlights Only is the threshold — the gate that decides which pixels bloom. At 0, everything above black contributes; raise it and only true highlights pass — the setting for lights-only glow on already-lit footage. Remember the gate reads the channel average, so colored sources gate lower than their brightest channel. Pair it with Highlight Rolloff, which widens the gate from a step into a ramp; a little rolloff is the difference between a gate you can see working and one you can’t.

The three colors stay white for the neutral law. Colorize tints the whole result, while Inner Tint and Outer Tint split the tint by distance — tinting only Outer Tint gives the atmosphere-style color fringing where the far field drifts in hue while the core stays honest.

Glow Only fades the source image out of the output — at 100 you get just the bloom, ready to composite over a graded plate on its own layer. Dimensions swaps the isotropic halo for Horizontal or Vertical smearing, a quick directional-bloom look. Quality steps the octave count; Q4 for finals, lower steps when previewing heavy comps.

The two macro dials ride the look you’ve already set: Master Amount multiplies Amount, Master Scale multiplies Size, and 100 is neutral. Build the glow with the underlying dials first, then animate one Master dial to pulse or fade the whole thing — one keyframed slider instead of two, and the balance you dialed in stays intact. Don’t animate a Master dial and the dial it folds at the same time, or the scaling doubles up.

Audio Drive lets a sound layer play the glow. Set Audio Layer to any layer in the comp that carries audio, choose what to listen to and what it moves, and the effect follows the track with no keyframes. The group sits collapsed at the bottom of the effect. With Audio Layer set to None, or Drive Amount at 0, it does nothing at all and the effect renders exactly as it would without it.

What it hears. Listen To picks the part of the sound that does the driving. Loudness follows the overall level. Hits reacts to transients such as drum hits and impacts, and a strong hit pulses harder than a soft one. Bass, Low Mids, Mids, Highs and Air each follow one frequency band (roughly 20 to 120 Hz, 120 to 500 Hz, 500 Hz to 2 kHz, 2 to 8 kHz and 8 to 20 kHz). The drive hears the layer’s audio where it sits in the timeline, following the layer’s start time and any time stretch, but it ignores time remapping, trims, Levels and audio effects on that layer. So turning a layer down in the mix does not weaken the drive.

Shaping the signal. For Loudness and the bands, the level becomes a signal between two marks. Audio Threshold is the floor in dB: anything quieter reads as nothing. Audio Range is how many dB above the floor it takes to reach full signal. The defaults (a floor of -40 dB and a range of 40 dB) spread the whole swing from -40 dB up to 0 dB. Raise the floor to ignore room noise or quiet passages, and narrow the range for a jumpier reaction. Audio Attack and Audio Release, in milliseconds, set how fast the signal rises and falls; the defaults (10 and 180) rise quickly and fall back more slowly.

For Hits, Hit Threshold sets how far a transient has to stand out from the surrounding audio to count, so higher values keep only the strongest hits. Hit Decay is how long each hit’s pulse takes to fade, in milliseconds. Audio Sync Offset slides the reaction against the picture, in milliseconds: positive values make the picture react later, negative values earlier.

How hard it pushes. Drives picks the target and Drive Amount sets the depth. At the default 100, the target swings from zero in silence to twice its dialed value at full signal, passing through the value you dialed halfway. Lower amounts narrow that swing around your value, higher amounts widen it, and negative amounts flip it, so the target drops as the sound gets louder (a ducking effect).

What it moves. Drives has two targets. Amount rides Master Amount, so the bloom’s strength follows the sound. Size rides Master Scale, so its reach grows and shrinks; Size driven by Bass makes the halo swell with the low end. Because the drive works through the Master dials, the balance you set with Amount, Size and the rest stays intact.

While a drive is active the glow re-renders on every frame, even over a still image. With the drive off it caches as usual.

More than one driver. Add Driver opens another driver inside the group, up to four in all, so one track can drive several things at once. A second driver has its own Listen To 2, Drives 2 and Drive Amount 2, plus a collapsed Response 2 group with its own Audio Threshold 2, Audio Range 2, Audio Attack 2, Audio Release 2, Hit Threshold 2 and Hit Decay 2. Drivers 3 and 4 repeat the same set with their own number. Remove Driver takes the last driver away. Every driver shares the Audio Layer and the Audio Sync Offset. Two drivers on the same target multiply their effects. The number of open drivers is kept in a hidden Drivers setting that the two buttons change for you.

Each frame works out its drive from the audio around it, so scrubbing, rendering in order or rendering out of order all give the same result.