Judder is a visible unevenness of motion in video, in which movement that should be smooth appears to stutter in a regular, rhythmic pattern. In Video quality, the term most often describes the artifact created when content is displayed at a refresh rate that is not an integer multiple of its frame rate, so some frames stay on screen longer than others; the classic case is 24 frames per second film shown on a 60 Hz display.
The word is also used more loosely for the inherent low-frame-rate stepping of 24 fps footage during camera pans, even when every frame is displayed for equal time. Distinguishing these two meanings is the first step in diagnosing a complaint, because they have different causes and different fixes.
How cadence mismatch creates judder
A display refreshes at a fixed rate, and each source frame must occupy a whole number of refresh cycles. When 24 fps content meets a 60 Hz screen, 60 divided by 24 equals 2.5, so frames cannot be shown for equal time. The common solution, 3:2 pulldown, holds one frame for three refreshes and the next for two, repeating the pattern.
The result is that alternate frames last about 50 milliseconds and 33.3 milliseconds instead of a steady 41.7 milliseconds. Motion that should move the same distance every frame instead advances in uneven time steps, which the eye perceives as a regular hitch, most noticeable on slow pans and scrolling credits.
| Display refresh rate | Refreshes per film frame | Cadence | Judder from mismatch |
|---|---|---|---|
| 48 Hz | 2 | 2:2 | None |
| 50 Hz | About 2.08 | Speed-up or irregular repeats | Present unless content is sped up to 25 fps |
| 60 Hz | 2.5 | 3:2 | Clearly visible |
| 72 Hz | 3 | 3:3 | None |
| 120 Hz | 5 | 5:5 | None |
A subtler form arises from the difference between 23.976 fps and 24.000 Hz. A display running at exactly 24 Hz while playing 23.976 fps content must repeat one frame roughly every 42 seconds, producing an occasional isolated hitch.
Judder compared with related motion artifacts
Several motion defects look similar to untrained eyes. The table separates them by pattern and cause, which guides the correct fix.
| Artifact | Pattern | Typical cause |
|---|---|---|
| Cadence judder | Regular, rhythmic hitch | Frame rate and refresh rate mismatch |
| Strobing | Stepped motion with sharp edges | Low frame rate with a short shutter |
| Stutter | Irregular, random hitches | Dropped or duplicated frames from decoding or performance problems |
| Motion blur | Smeared moving objects | Long shutter or slow display response |
| Ghosting | Faint trailing copies | Pixel response or interpolation errors |
The key test is regularity. A repeating pattern points to cadence judder, while hitches at random moments usually indicate stutter from dropped frames, which no cadence setting will fix.
Why some displays and shots show more judder
Visibility depends on both the content and the screen. Fast-response displays such as OLED panels switch pixels almost instantly, so each held frame appears as a crisp step; slower LCD panels blur transitions slightly and can mask the effect.
- Pan speed: slow and medium pans across detailed scenes reveal judder most, because the eye tracks the motion.
- Shutter angle: a 180-degree shutter adds natural motion blur, while short shutters produce sharper steps.
- Screen size and viewing distance: larger angular size makes each positional jump bigger.
- Brightness and contrast: high-contrast edges such as bright window frames make steps easier to see.
Cinematographers manage the inherent 24 fps stepping by limiting pan speed so that an object takes several seconds to cross the frame, and by keeping a standard shutter angle. Cadence judder, by contrast, is a playback problem that cannot be corrected during shooting.
How to reduce or remove judder
The most effective remedy is to match the display’s refresh rate to the content frame rate or to an integer multiple of it. Many streaming devices, media players and televisions offer a frame rate matching option that switches the output for each title.
| Remedy | How it works | Side effect |
|---|---|---|
| Refresh rate matching | Output switches to 24 Hz or a multiple | Brief blank screen during mode change |
| 120 Hz or 240 Hz panels | Allow even 5:5 or 10:10 cadence | Requires correct signal detection |
| Variable refresh rate | Display follows the source timing | Support for video playback varies |
| Motion interpolation | Creates intermediate frames | Soap opera effect and interpolation artifacts |
| Low-level dejudder setting | Partial interpolation | Reduces judder but alters the filmic look |
Interpolation is controversial. It removes judder but can create the soap opera effect, an unnaturally smooth video look, and it often introduces halos around moving objects. Filmmaker modes on many televisions therefore turn interpolation off and rely on cadence-correct playback instead.
Judder in production and post-production
Conversions between frame rates are a common source of baked-in judder that no display setting can remove. Converting 24 fps to 30 fps by repeating fields or frames permanently embeds the 3:2 pattern, and careless conversion between 25 and 30 fps families produces irregular duplicates.
| Conversion | Common method | Judder risk |
|---|---|---|
| 24 to 25 fps | Speed-up of about 4% | None, but audio pitch and runtime change |
| 24 to 29.97 fps | Telecine with 3:2 pulldown | Embedded cadence judder |
| 25 to 29.97 fps | Frame duplication or optical flow | Irregular hitches unless motion-compensated |
| 30 to 24 fps | Frame dropping | Uneven motion and lost moments |
The safest workflow is to deliver in the native frame rate and let the playback device handle cadence. When a conversion is unavoidable, motion-compensated conversion gives the smoothest result, at the cost of processing time and possible artifacts.
The idea in brief
Judder is the jerky, uneven motion you sometimes notice when a camera pans slowly across a scene in a film. It often happens because a television shows pictures at a different pace than the film was made for.
Think of a marching band where every second step is a little longer than the others. The rhythm feels off even though everyone keeps walking. Setting the screen to the film’s own pace usually makes the motion steady again.
A practical scenario
A home theater owner notices a regular hitch during slow pans in a 24 fps film played from a streaming device into a modern OLED television. Panning shots over a city skyline look as if the image steps forward unevenly.
The streaming device is set to output a fixed 60 Hz signal, which forces 3:2 pulldown. The owner enables the device’s frame rate matching option, so the television now receives 24 Hz and displays each frame for five refreshes of its 120 Hz panel. The television’s motion interpolation remains off to preserve the original look.
The skyline pans now move with even timing. A small amount of inherent 24 fps stepping remains on fast pans, but the rhythmic cadence judder disappears, confirming that the problem was the playback chain rather than the film itself.