Keyframes have a reputation for being the hard part of video editing. They are not hard. They are two numbers. What is genuinely hard is the curve between them, and almost nobody explains that.

What a keyframe is

A keyframe records a value at a moment in time. Scale is 100 percent at zero seconds. Scale is 110 percent at four seconds. That is two keyframes.

The software fills in everything between. At two seconds it is 105 percent, unless you told it otherwise. That filling-in is called interpolation and it is the entire craft.

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

The curve is the whole game

With linear interpolation, the value changes at a constant rate. It starts instantly at full speed and stops instantly at the end.

Nothing in the physical world does that. Objects accelerate and decelerate. A camera operator pushing in starts slowly, reaches a speed, and slows as they arrive. A linear keyframe move looks wrong for a reason you can feel but might not name: it starts and stops with infinite acceleration.

Ease out means it starts slowly. Ease in means it ends slowly. Ease in and out on both keyframes is the default that makes almost every move look considered instead of mechanical, and it is a single setting.

If you learn one thing about keyframes, learn to put an ease on both ends. It is more of an improvement than any number of extra keyframes.

The bezier editor

Beyond named eases, the curve itself can be shaped by dragging handles. This is where you go when a preset ease is close but not right: a move that should hang at the end, a bounce, an accelerating push that never quite settles.

It is worth understanding but not worth starting with. The order that works is: two keyframes, then an ease, then a custom curve only if the ease is genuinely wrong.

Two keyframes, not ten

The most common beginner failure is too many keyframes. Every extra one is a moment where the motion changes direction or speed, and a move with six keyframes usually has five places where it stutters.

Almost every good camera move in a video is two keyframes. Start value, end value, ease on both. If it is not working, the fix is usually different values or a different duration, not more points.

Three keyframes is a legitimate shape when something moves, holds, and moves again. Four is rare. If you are at seven, something has gone wrong.

What is worth keyframing

Scale and position. The push-in, the drift, the reframe. See adding a camera move to a static video for the amounts.

Opacity. Fading an overlay, a title, a logo in and out.

Effect intensity. A blur that comes on as something enters, a grade that shifts across a scene change.

Volume. Though most volume work is better done with dedicated audio ramps.

Where they live in Zella

Motion keyframes and the bezier curve editor sit behind the Advanced tools toggle in the editor's top toolbar, alongside live luma scopes, Color Match and effect masks.

That toggle is off by default, and that is a deliberate choice rather than an accident: most videos never need a hand-built curve, and a beginner opening an editor full of controls they cannot yet use is a worse experience than one that reveals them on request.

If what you want is a push-in and not a lesson in interpolation, animating a zoom without keyframes covers the version where the software sets both points for you.

The practical order

  1. Decide what should change and by how much
  2. Set the value at the start, set it at the end
  3. Ease both
  4. Watch it. If it looks mechanical, the ease is missing. If it looks fussy, there are too many keyframes. If it looks fine but you noticed it, it is too big or too fast

That last line is the same rule as everywhere else in motion: the move that works is the one you feel rather than see.

Apple's Final Cut Pro documentation covers the same keyframe and curve model in a professional context if you want the deeper reference.

Common questions

Why does my keyframed move look robotic? Because it is linear, so it starts and stops at full speed. Nothing physical does that. Adding an ease to both keyframes fixes more than any number of extra points.

How many keyframes should a move have? Two. Start value, end value, ease on both. Three is legitimate for move-hold-move. If you are at seven, something has gone wrong.

What is the bezier curve editor for? Shaping the curve by hand when a named ease is close but not right, such as a move that should hang at the end. It is not where to start.