24 fps judder on 60 Hz screens, and why 120 Hz fixes it

A 24 fps movie stutters on a 60 Hz screen because 60 cannot be divided evenly by 24, forcing the display to alternate between showing one frame for 3 refreshes (50 milliseconds) and the next frame for 2 refreshes (33.33 milliseconds). This uneven 3:2 cadence introduces a 16.67-millisecond timing disparity between alternating frames, producing the rhythmic visual hitch known as telecine judder.

120 Hz screens fix this through basic arithmetic: 120 divided by 24 is exactly 5. By holding every single film frame for exactly 5 screen refreshes (41.67 milliseconds), a 120 Hz display delivers perfectly uniform 5:5 cadence, restoring the authentic motion timing of a 35mm cinema projector without artificial motion smoothing.

Animation

24 fps on a 60 Hz screen vs a 120 Hz screen

60 Hz screenframe held 3 refreshes

ABCDEF

120 Hz screen (ProMotion)frame held 3 refreshes

ABCDEF

What is 3:2 pulldown and why is it necessary on 60 Hz monitors?

To understand why telecine judder occurs, look at the mathematics of refresh rates. Standard computer monitors, office displays, and older televisions refresh their panels at a fixed frequency of 60 Hertz—meaning the screen draws a new image exactly 60 times every second.

However, feature films have been standardized at 24 frames per second since the introduction of synchronized sound in 1927. To understand the historical reasons cinema adopted this rate, read our history of why movies are 24 fps.

If you divide 60 screen refreshes by 24 video frames:

60 / 24 = 2.5 refreshes per frame

A physical display panel cannot show a frame for half of a refresh cycle. An LCD or OLED panel updates sequentially from top to bottom on discrete clock pulses. Because a display cannot draw 2.5 refreshes, the video rendering engine must round the duration up and down:

• Frame 1: Displayed for 3 screen refreshes (3 / 60 s = 50.0 ms)
• Frame 2: Displayed for 2 screen refreshes (2 / 60 s = 33.33 ms)
• Frame 3: Displayed for 3 screen refreshes (3 / 60 s = 50.0 ms)
• Frame 4: Displayed for 2 screen refreshes (2 / 60 s = 33.33 ms)

This pattern, known in the broadcast industry as 3:2 pulldown (or 2:3 pulldown), distributes four film frames across ten display refreshes:

(3 + 2 + 3 + 2) / 60 = 10 / 60 = 4 / 24 = 0.1667 seconds

Over an entire second, all 24 frames are successfully shown. However, within that second, every odd-numbered frame lingers on your retina 50 percent longer than every even-numbered frame.

During static dialogue scenes where characters sit motionless, this timing asymmetry is virtually invisible. But the moment the camera executes a slow, continuous horizontal pan across a city skyline, a landscape, or a room, the flaw becomes glaring. Vertical structures—such as lampposts, window frames, and skyscrapers—appear to judder, vibrating forward with an unnatural, halting rhythm instead of gliding smoothly across the field of view.

What is the difference between judder and stutter?

In home theater communities and technical forums, the terms “judder” and “stutter” are frequently conflated, but they describe entirely different optical phenomena with distinct technical causes:

Telecine judder is purely a temporal cadence problem. It occurs because the display controller draws frames unevenly across time.

Display stutter, on the other hand, is an optical consequence of modern fast-response display panels. Traditional liquid crystal displays (LCDs) have slow pixel response times (5 to 15 milliseconds); when a pixel transitions between colors, it takes time to twist the liquid crystals, creating a slight physical smearing that naturally softens the jump between 24 fps frames.

OLED panels have near-instantaneous pixel response (well under a millisecond). When a 24 fps film plays on an OLED screen, each frame appears instantly, stays frozen as a razor-sharp still image for 41.67 milliseconds, then snaps to the next. With no transition blur to soften the jump, slow pans can look like a strobe, even with a perfect 120 Hz cadence. (Mini-LED screens such as the MacBook Pro’s are LCDs, with the slower pixel response of LCD.)

Why are some files 23.976 fps instead of true 24.000 fps?

When inspecting video file metadata on your Mac, you will notice that almost all commercial movies and television shows are tagged not as 24.000 fps, but as 23.976 fps (or more precisely, 24000 / 1001 fps).

This fractional rate is a historical hangover from the birth of American color television in 1953:

1. When the National Television System Committee (NTSC) introduced color broadcasting, engineers needed to interleave a high-frequency color subcarrier signal (3.579545 MHz) into the existing black-and-white broadcast spectrum.
2. If the broadcast frame rate remained at exactly 30 fps (60 Hz field rate), harmonic interference between the 4.5 MHz audio carrier and the color subcarrier created visible crawling dots on television screens.
3. RCA and NTSC engineers solved the interference by shifting the transmission speed down by exactly 0.1 percent, establishing a broadcast rate of 60 * (1000 / 1001) = 59.94 fields per second.
4. When 24 fps feature films were transferred to videotape for broadcast, they were slowed down by that identical 0.1 percent margin: 24 * (1000 / 1001) = 23.976 frames per second.

This fractional standard persists today. Most American television productions, Blu-ray discs and streams are still 23.976 fps, while digital cinema packages (DCPs) for theaters use exactly 24.000 fps.

The periodic hitch

This subtle 0.1 percent speed difference creates a hidden playback artifact on computer displays.

If your Mac’s screen runs at exactly 60.000 Hz and you play a 23.976 fps movie:

60.000 / (24000 / 1001) = 2.5025 refreshes per frame

The 3:2 pattern averages 2.5, so the video falls behind by a quarter of a percent of a refresh with every frame: one whole refresh every 400 frames, about every 16.7 seconds. To stay in sync with the audio, the player has to hold one frame a refresh longer that often, an occasional extra hitch on top of the judder. (On a 24.000 Hz display, the same mismatch costs a whole frame about every 41.7 seconds.) Choosing 59.94 Hz or 47.95 Hz makes the numbers line up exactly.

How does 120 Hz ProMotion solve 24 fps judder?

120 Hz display panels make telecine judder avoidable.

Every 14-inch and 16-inch MacBook Pro since 2021 has a Liquid Retina XDR display with ProMotion, Apple’s adaptive refresh rate, up to 120 Hz.

When you play a 24.000 fps film on a 120 Hz screen, the math aligns into a clean integer:

120 / 24 = 5.0 refreshes per frame

Instead of alternating between 3 refreshes and 2 refreshes, the display uses uniform 5:5 pulldown:

• Frame 1: Displayed for 5 refreshes (5 / 120 s = 41.67 ms)
• Frame 2: Displayed for 5 refreshes (5 / 120 s = 41.67 ms)
• Frame 3: Displayed for 5 refreshes (5 / 120 s = 41.67 ms)
• Frame 4: Displayed for 5 refreshes (5 / 120 s = 41.67 ms)

Every film frame gets the same time on screen. The 16.67 ms difference of 3:2 pulldown disappears, and pans, tracking shots and walks move with the even cadence the cinematographer intended, as long as the player hands each frame to the display on time.

How to configure fixed refresh modes in macOS System Settings

If you are using an external display—such as the Apple Pro Display XDR or a high-end reference monitor—your display may operate at fixed refresh rates rather than variable ProMotion rates. While the Pro Display XDR does not feature 120 Hz ProMotion, Apple engineered it with studio-grade fixed refresh modes specifically for video post-production.

Apple’s own advice, in its guide to changing the refresh rate on a MacBook Pro or Apple display, is to choose a refresh rate that divides evenly into your content’s frame rate, such as 48 Hz for 24 fps. Here is how:

1. Open the Apple menu and select System Settings.
2. Click Displays in the left-hand sidebar.
3. Select your display icon at the top of the window.
4. Locate the Refresh Rate pop-up menu.

Depending on your display, macOS offers these fixed rates alongside ProMotion (or 120 Hz):

• 47.95 Hertz: Delivers perfect 2:2 pulldown for 23.976 fps film transfers (2 * 23.976 = 47.952 Hz), eliminating both 3:2 judder and the 41-second clock drift glitch.
• 48.00 Hertz: Delivers exact 2:2 pulldown for true integer 24.000 fps digital cinema files (2 * 24.000 = 48.000 Hz).
• 50.00 Hertz: Matches European PAL broadcast video standards (25 fps / 50 fps).
• 59.94 Hertz: Matches NTSC broadcast video standards (29.97 fps / 59.94 fps).
• 60.00 Hertz: Standard computing refresh rate for web browsing and desktop work.

When you set your display to 48.00 Hz or 47.95 Hz, the screen refreshes at twice the speed of the film. Each frame flashes exactly twice (2:2 pulldown), replicating the mechanical double-bladed shutter mechanism of authentic 35mm theatrical projectors.

What about frame interpolation as an alternative?

If you are watching video on an office monitor or laptop screen that only supports a fixed 60 Hz refresh rate and lacks 48 Hz or 120 Hz modes, you have two choices:

1. Accept 3:2 Pulldown: Watch the movie in its native 24 fps state, tolerating the slight telecine judder during horizontal camera pans.
2. Apply Motion Interpolation: Use video software to mathematically synthesize intermediate frames, converting 24 fps into a smooth 60 fps stream.

Motion interpolation eliminates telecine judder because the resulting 60 fps video matches the 60 Hz display refresh rate one-to-one. However, as explained in our guide to motion interpolation and the soap opera effect, frame generation alters the aesthetic texture of the film, smoothing out optical motion blur and occasionally introducing edge tearing and halo artifacts around fast-moving actors.

For viewers who prioritize authentic film texture, native refresh rate matching via 120 Hz ProMotion or 48 Hz cinema modes is always superior to artificial frame synthesis.

Enjoying judder-free cinema on a Mac

Telecine judder is not an inevitable fact of digital video; it is a legacy artifact of the awkward meeting between 1920s sound film speeds and 1950s television standards.

By pairing 24 fps content with modern 120 Hz ProMotion displays or selecting dedicated 48 Hz and 47.95 Hz cinema refresh rates in macOS, you eliminate 3:2 pulldown at the hardware level. Every frame receives identical temporal weight, letting you experience movies with the steady, natural rhythm the director intended. And if you’d rather have smooth motion, MacLC can interpolate frames up to your screen’s refresh rate, for free.