Setting a clip to 2x is a speed change. Gliding from 0.5x up to 2.5x and back down across the same clip is a speed ramp, and it reads completely differently.

What a ramp actually is

A plain speed change applies one multiplier to the whole clip. A ramp applies a curve: the multiplier is a function of how far through the clip you are. At the start it might be 0.5, in the middle 2.5, at the end 0.5 again.

The clip's total length on the timeline stays what you asked for. What changes is the distribution of source frames inside it, which is why a ramp can feel dramatic without pushing everything after it out of sync.

An editing timeline: video clips, a zoom keyframe and an audio track below.

Why a ramp reads better than a hard change

Attention follows change, and the eye reads an abrupt speed switch as an error before it reads it as a choice. A ramp gives the viewer a beat to understand what is happening, which turns the same information into a deliberate move.

The practical version: if the audience notices the technique before they notice the subject, you ramped too hard or too fast.

The five shapes

Ramp Curve Where it belongs
Slow to Fast to Slow Slow ends, fast middle Skipping the boring middle of an action while keeping both ends readable
Fast to Slow to Fast Fast ends, slow middle Landing on a moment: the click, the reveal, the reaction
Freeze Frame Drops to a near-still hold mid-clip A beat of emphasis you can talk over
Ramp from 0% Eases up out of a near-freeze Coming out of a hold into motion
Ramp to 0% Eases down into a near-freeze Arriving at a hold, then cutting

The last two are a matched pair and are worth learning together, because most of the ramps people admire in other people's videos are one of them.

On Zella for iPhone the set is four: Slow-Fast-Slow, Fast-Slow-Fast, Ramp Up and Ramp Down.

Adding one in Zella

  1. Select the clip or the segment on the timeline.
  2. Turn on Advanced Tools in settings if you have not already. Ramps sit behind that switch on purpose, alongside keyframes and the curve editor, so a beginner's timeline is not full of controls they did not ask for.
  3. Right-click the segment and open the Speed Ramp menu.
  4. Pick a shape. The timeline block redraws at its new width immediately, so you can see what the ramp did to the pacing before you play it.

Plain speed control - slow, fast, freeze and reverse - is free on both apps and needs none of this. Speeding up or slowing down a clip covers that path, and ramps are part of the Pro depth toolset.

Two neighbouring tools in the same menu are worth knowing. Blade Speed at Playhead splits the segment where the playhead sits so the two halves can carry different speeds, which is how you build a ramp by hand when none of the five shapes is the one you want. Instant Replay inserts a copy of the selected segment right after it at a half, quarter or matched speed.

Where ramps earn their keep

  • A screen recording with one important click. Ramp fast through the navigation, slow into the click, cut. The viewer never waits and never misses the point.
  • A product shot. Ramp to 0% arriving at the hero angle, hold, then cut on the beat.
  • Anything with a physical action. A pour, a door, a hand entering frame. Fast to Slow to Fast puts the weight exactly where the action is.

Where they do not earn it: talking heads. Ramping a face makes the voice unusable, and the audio is the content.

What happens to the audio

This is the part people discover late. Retiming video retimes the audio bonded to it, and a ramp makes that audio unlistenable by design - the pitch slides with the speed. Apple's audio fundamentals is a short read on why that happens and what editors do about it.

Two ways round it, both normal practice:

  • Detach the audio from the clip before you ramp, so the voice keeps its own timing while the picture moves.
  • Ramp only shots you do not need the sound from, and carry the audio from a neighbouring clip underneath. That is a J-cut or an L-cut, and it is the standard way ramped footage is scored.

Music underneath is unaffected, which is why ramps and a bed go together so naturally. Landing a Ramp to 0% on a downbeat is most of what makes a montage feel edited rather than assembled.

Frequently asked questions

Is a speed ramp the same as slow motion? No. Slow motion is one speed applied to a whole clip. A ramp moves between speeds across the clip, so the change itself is part of what the viewer sees.

Do I need keyframes to make one? Not in Zella - the five shapes carry their own curves. Keyframes are there if you want a curve none of them gives you, behind the same Advanced Tools switch.

Will a ramp change how long my clip is? The clip keeps the duration the ramp resolves to, and everything after it shifts by the difference like any other length change. The ramp redistributes frames inside that window rather than stretching the timeline unpredictably.

Why does my voice sound strange after ramping? Because the audio was retimed with the picture. Detach the audio first, or carry sound from an adjacent clip underneath.

Is a ramp free or does it need Pro? Plain slow, fast, freeze and reverse are free on both apps. Ramps, Blade Speed and Instant Replay are part of the Pro depth toolset.

How many ramps should one video have? Usually one or two. A ramp is emphasis, and a video where everything is emphasised has emphasised nothing.