1 The idea
A shake has three main settings: frequency (how fast it jitters), amplitude (how strong) and decay (how quickly it fades). In comp, key the amplitude only and keep the frequency constant, because keying the frequency makes the noise inside lurch or race unnaturally.
Light from a blast reaches the camera almost instantly, but the shockwave travels at about the speed of sound. From a blast 170 m away, the shockwave arrives about half a second (12 frames) after the flash. Beginners often shake on the flash frame, which loses the sense of distance and scale.
delay = distance ÷ 343 m/s · offset = A · e^(−decay·t) · noise(freq · t)2 Hands-on
Task: start the shake when the shockwave arrives, strong enough to see (≥ 4 px), fading to ≤ 10% before the loop ends
Find the cyan line on the timeline and the “shockwave reaches camera” label, then try the spark motion-blur switch
3 Deep dive
Shake timing sells scale and distance
Light arrives at once, but the shockwave and sound arrive later depending on distance. A distant blast has a gap between flash and shake, and that gap is what makes the audience feel it is big and far away. Shake on the flash and the blast feels small and close.
| Distance | Lag after flash | Frames @24 |
|---|---|---|
| 43 m | 0.125 s | 3 |
| 172 m | 0.5 s | 12 |
| 343 m | 1 s | 24 |
| 1 km | 2.9 s | 70 |
Distance ÷ 343 = seconds to wait; × 24 gives frames.
Key the amplitude only
Frequency is how fast the noise inside the shake is read. Key it over time and the read position races or rewinds, giving odd lurches. Keep frequency constant and control strength with amplitude alone. For several events, use a separate shake per event.
A good shake often has layers: small fast jitter, the main impact, and a slow drift. Each layer keeps its own constant frequency.
- 1Flash (no shake)
- 2Shockwave arrives
- 3Amplitude spikes
- 4Decay fades it
Motion blur and shake
Use the shake node’s own motion blur (a shutter around 0.5, centred) on the plate and on any CG that has no shake blur of its own. A spark streak already is the motion blur of a bright dot; the shake’s 2D blur on top gives a fat straight line instead of the curved path it should trace. Send elements with strong built-in streaks, such as sparks, through a second copy of the same shake (linked knobs) with its motion blur off, then merge them back into the shaken comp. Best of all, render the shake into the CG camera so the streaks come out curved from the start.
Its place in the stack: shake goes after glow and flares and always before grain. Grain is the last node; shaking after it moves and blurs the grain.
4 In real work
In Nuke
- CameraShake: key only the amplitude, keep frequency constant, use the node’s motion blur on the plate and CG (sparks get a linked copy with blur off).
- Or build one with a Transform: a noise() expression on translate, multiplied by an amplitude you key in a separate knob.
- Allow overscan or scale up slightly so no black edge shows during the shake.
- Place it after glow/flares and before the Grain, which stays last.
- Judge timing from cache at full speed; stepping frames can’t judge rhythm.
Common mistakes → the fix
- ✗ Shaking on the flash frame of a distant blast✓ Start it when the shockwave arrives (distance ÷ 343 seconds).
- ✗ Keying frequency up for the impact✓ Keep frequency constant and raise amplitude instead.
- ✗ Adding a MotionBlur over sparks after the shake✓ Sparks already carry blur; run them through a linked copy of the shake with motion blur off, or render the shake into the CG camera.
- ✗ Shake after grain✓ Grain must be last; move the shake above it.
Before you send the shot
- The shake starts on the shockwave’s arrival, not the flash
- Only amplitude is keyed; frequency is constant
- No single frame with an extreme smear or jump
- No frame edges show during the shake
- Sparks aren’t double-blurred, and grain is last
5 Check yourself
A spark element is rendered with motion blur. You add a 2D camera shake on top. What about blur?
🔒 Answer the question above and this card opens
1. A blast 686 m away, at 24 fps: roughly how many frames after the flash should the shake start?
2. You want the impact to hit harder at the start. What do you change?
Where the numbers come from: Uses 343 m/s for sound (dry air at about 20 °C) and treats light as instant. A strong blast’s shockwave is faster than sound close to the source and slows towards the speed of sound with distance, so the numbers are approximate. The shake “noise” here is a sum of three sines standing in for a real shake tool’s noise. The blast is drawn in code.