Frame rates, regions and why 29.97
The frame rate has to be chosen before the first shot. It decides how motion looks, where the video can be shown and even whether your lights will flicker.
What the frame rate changes
The frame rate determines two things at once: how often the camera ‘looks’ at the world and how much time each frame covers. At 24 fps there are almost 42 ms between two frames — enough for a fast-moving object to travel a fair way across the picture. The eye fills in the gaps, but we perceive them as typical ‘filmic’ motion with a slight judder on fast pans. At 50 or 60 fps the jumps are half as big and motion is smooth and ‘live’ — which is why sport and live broadcasts use it, and why to some viewers a drama shot that way looks like television.
The frame rate doesn’t change how sharp an individual frame is — that is controlled by the shutter speed. At the same shutter angle, though, a higher frame rate means a shorter exposure, and so less blur and a need for more light.
INTERACTIVE · FRAME RATE EXPLORER
Frame rate comparison
Measuring your display’s refresh rate…
A monitor or phone can show at most as many different images per second as its refresh rate — typically 60 Hz. So on most displays you won’t see 120 fps in real time. That is why the tool has slow motion: at ¼ speed a 30 Hz display is enough for 120 fps, and the frame timing stays exact.
A map of frame rates
| fps | Exact value | Where it is used |
|---|---|---|
| 24 | 24 or 24/1.001 = 23.976 | Cinema, feature films, series. Digital cinema to the DCI specification must support 24.000 fps. 23.976 is the variant for TV and streaming in 60 Hz regions. |
| 25 | 25.000 | Broadcasting and production in regions with 50 Hz mains — Europe including Slovakia, most of Africa, Asia and Australia (former PAL/SECAM territories). |
| 30 | 30/1.001 = 29.97 (also 30.000) | Broadcasting in regions with 60 Hz mains — USA, Canada, Mexico, South Korea, part of Japan (former NTSC). On the web and on phones, exactly 30 as well. |
| 50 | 50.000 | Sport, live broadcasts and a ‘live’ look in 50 Hz regions; 2× slow motion in a 25 fps project. |
| 60 | 60/1.001 = 59.94 (also 60.000) | Sport and live broadcasts in 60 Hz regions, game capture, computer screens. |
| 120 | 120 or 119.88 | Shooting for slow motion (5× when played back at 24 fps). Real-time playback requires a display of ≥ 120 Hz. |
ITU-R BT.709, the recommendation for HDTV, explicitly defines frame rates of 60, 50, 30, 25 and 24 Hz, and for 60, 30 and 24 also variants divided by 1.001. That is where the awkward numbers 59.94, 29.97 and 23.976 come from.
Why Europe has 25 and America 29.97
The first television standards synchronised scanning with the frequency of the electricity mains so that interference from the mains would ‘stand still’ in the picture rather than drift. In 50 Hz countries this gave 50 fields (25 frames) per second, in 60 Hz countries 60 fields (30 frames). When NTSC colour broadcasting was introduced in the USA, the rate was lowered by 0.1% (divided by 1.001) so that the colour subcarrier would not interfere with the sound carrier. So 30 became 29.97 and 60 became 59.94. For compatibility, this division survived into the digital era and was carried over to 23.976 as well.
The practical consequence today: frame rates still follow the region, both because of broadcasting and because of lighting. Mains-powered lights flicker at twice the mains frequency, and the shutter speed has to match that rhythm. Anyone shooting 30 fps with a 1/60 s shutter under fluorescent lights in Slovakia risks flicker; 25 fps at 1/50 s is safe.
Slow motion and fast motion
Slow motion is created when footage shot at a higher frame rate is played back at a lower one. Factor = capture frame rate ÷ project frame rate.
| Shot at | in 24 fps | in 25 fps | in 30 fps |
|---|---|---|---|
| 48 fps | 2× | 1.92× | 1.6× |
| 50 fps | 2.08× | 2× | 1.67× |
| 60 fps | 2.5× | 2.4× | 2× |
| 100 fps | 4.17× | 4× | 3.33× |
| 120 fps | 5× | 4.8× | 4× |
For smooth slow motion the camera really has to shoot at a high frame rate (labelled ‘high frame rate’ or ‘S&Q’). Slowing down normal footage in software calculates in-between frames — the result is an estimate of the motion, and complex movement produces artefacts.
Mixing frame rates in one project
A timeline has one frame rate. Everything else is conformed to it — and how the editing software does that affects the result:
- Whole multiples (50 → 25, 60 → 30) are the simplest: every other frame is dropped, or the footage is interpreted as slow motion.
- 25 ↔ 24 is handled in practice by speeding up / slowing down by 4.17% (25/24) — the so-called PAL speed-up. Both the duration and the pitch of the sound change, and the pitch has to be corrected.
- 29.97 ↔ 25 has no simple ratio. The conversion either repeats / drops frames (visible judder) or blends and interpolates motion (blur, artefacts). Professional conversion uses specialised tools.
- 23.976 vs. 24.000 — you won’t see a 0.1% difference in a short shot, but over an hour it adds up to 3.6 seconds. Separately recorded sound drifts out of sync with the picture.
Timecode and drop-frame
Timecode addresses every frame as HH:MM:SS:FF. At 25 fps this is straightforward: frames 00 to 24, then the next second. At 29.97 fps, though, timecode counted at 30 frames per second would drift 3.6 seconds from the clock over an hour. Drop-frame timecode solves this by skipping frame numbers 00 and 01 at the start of every minute — except every tenth minute. No picture frames are dropped, only numbers. Drop-frame is usually marked with a semicolon before the frames: 01:00:00;00.