Why You Shouldn’t Always Shoot at 120fps+: High Frame Rates Aren’t Free

Your new action camera can shoot at 60fps, 120fps, maybe even 240fps or more. Camera manufacturers are understandably happy to put those numbers on the box.

It's pretty easy to assume that a higher frame rate means better video. If 30fps is good, surely 120fps must be four times better, right?

There are good reasons to shoot at high frame rates, especially if you want slow motion or if you want to use speed ramping. But if the finished footage is going to play at normal speed, using the highest frame rate available can come with some real tradeoffs.

The basic question is pretty simple: do you actually need all those extra frames?

What does a higher frame rate give you?

Frame rate is how many individual "pictures" the camera captures each second.

Shoot 30fps and you get 30 samples of motion every second. At 60fps you get 60. At 120fps you get 120.

That extra temporal information is extremely useful when you want to slow footage down:

If you know you want a dramatic slow-motion shot, 120fps or 240fps can be exactly what you need.

But if you are going to play the footage back at normal speed, there is more to consider.

For a deeper explanation of how frame rate affects the way motion looks, see Frame Rate, Motion Blur, and the Cinematic Look.

Higher frame rates give you more flexibility when changing speed

Higher frame rates are useful if you plan to change a clip’s speed in editing.

Even a small speed change can make the original frames stop lining up neatly with your timeline. The editor may then have to drop frames, repeat them, or create new ones using interpolation. All of those methods have drawbacks, and usually result in video that isn't perfectly smooth

With 60fps or 120fps footage, there are more frames available to work with, so speed changes are generally easier to keep smooth because dropping a frame of 1/120th of a second is much less noticeable than one that is 1/30th of a second long. Speed ramps are the toughest case, since the playback speed is constantly changing.

If you expect to change clip speeds much, a higher capture frame rate gives you more flexibility and can help avoid stutter, ghosting and interpolation artifacts.

See Edit Adventure Footage Without Making It Boring for more editing tips.

There are clearly some very good reasons to use a high frame rate: If you need slow motion, speed changes, or extra temporal detail, those additional frames can make your video look better.

The tradeoff is that capturing all those extra frames puts more demands on the camera. That can affect compression, exposure, storage, and sometimes the shooting modes available to you.

More frames put more pressure on compression

This is one of the less obvious drawbacks of shooting everything at a high frame rate.

A camera shooting 120fps has four times as many frames to encode and store as it does at 30fps. In most cameras, the recording bitrate does not increase by four times to compensate for all the extra frames.

That matters most with exactly the kind of footage action cameras are often used for - Grass, trees, leaves, gravel, rocky trails, water and other highly detailed textures are difficult to compress cleanly. When the camera is moving, all of that fine detail is changing from frame to frame.

Give the encoder a lot more frames to deal with without a proportional increase in bitrate and it can run out of room. Fine textures can start to look soft, blocky or mushy, particularly while the camera is moving quickly.

You may have seen footage where a forest looks detailed when the camera is still, then suddenly turns into green mush when you start riding or flying. Compression is often part of the reason.

There is a little more going on than simply dividing the bitrate by the number of frames. Modern video codecs such as H.264 and H.265 reuse information from nearby frames instead of encoding every frame as a completely separate photograph. Frames at 120fps are also closer together in time, which helps compression.

That reduces the penalty, but complex moving detail can still put considerably more pressure on the available bitrate.

High frame rates need more light

There is another tradeoff that becomes important very quickly once the avaialble light starts to drop: If you keep the same shutter angle as you increase frame rate, the shutter has to get faster.

A traditional 180-degree shutter would look roughly like this:

Every time you double the frame rate, you halve the amount of time available to expose each frame - and halve the light that gets into the camera.

Going from 30fps to 120fps means that only 25% as much light hits the camer's sensor.

In bright sunlight that might not matter at all. Under trees, indoors, late in the day or in poor weather, it can matter a lot.

If there is not enough light for the faster shutter, the camera may have to raise ISO. On a small action-camera sensor, that usually means more noise and less usable fine detail.

This is also why an ND filter that works well at 30fps may be much too strong at 120fps. You already have much less exposure time available.

If you want a refresher on the relationship between ND, shutter speed and motion blur, see What do ND filters do? and our ND Filter Tips.

Your camera may give something else up

The highest frame-rate modes are often the most demanding modes a camera can run.

Depending on the camera, choosing 120fps or 240fps may affect things such as:

• maximum resolution
• stabilization options
• horizon leveling
• field of view
• HDR or Log recording
• bit depth
• codec or bitrate choices
• other image-processing features

This varies a lot from camera to camera, so it is worth checking what actually changes when you select the high-frame-rate mode.

Sometimes the trade is absolutely worthwhile. Sometimes you have given up a feature you actually wanted in exchange for frames you will never use.

There are some practical costs too

High-frame-rate modes often generate larger files and make the camera work harder.

That can mean more space on your memory card, more storage on your computer, longer transfers and more work for your editing system.

Depending on the camera and recording mode, it can also mean more heat and increased battery use.

Artificial lighting can also be a problem

Higher frame rates usually mean shorter exposure times, which can make flicker from artificial lighting more visible.

LED lights, streetlights, arena lighting and other electronically controlled light sources may pulse much faster than you can see with your eyes. A longer exposure can average some of that variation together. A very short exposure may capture it much more clearly.

That can show up as flickering brightness or bands moving through the image.

If you see that kind of problem, frame rate and shutter speed are both worth checking.

So when should you use a high frame rate?

Use it when those extra frames are doing something useful.

• If you know you want 4x slow motion, shoot 120fps.
• If you want a 2x slow-motion option , 60fps may be all you need.
• If you expect to change speeds significantly in editing, particularly with speed ramps, capturing more frames can make the output smoother.

For everyday normal-speed footage, 24, 25, 30, 50 or 60fps will often give you everything you need while leaving the camera more room for exposure, compression and other features.

A reasonable starting point is:

These aren't rules. Decide how you want the finished footage to look first, then choose the frame rate that gives you what you need.

And if your action-camera footage looks strangely choppy or jittery, frame rate is only one part of the equation. Shutter speed and motion blur matter too. See Why is my Footage Choppy or Jittery? for a more detailed look at that problem.

The highest number in the camera menu is an impressive capability. It just doesn't need to be the default.