Shutter Speed

Shutter Speed

noun | Camera & Optics

The length of time the camera's shutter remains open to expose each individual frame to light. A longer shutter speed allows more light and more motion to register per frame, producing brighter exposure and more motion blur. A shorter shutter speed allows less light and captures motion more crisply, producing darker exposure and sharper, more stroboscopic motion. In cinema, shutter speed is typically expressed as a shutter angle rather than a fraction of a second.

Quick Reference

The Explanation: How & Why

Each frame of a film or video recording is a discrete exposure. The shutter controls how long the sensor or film plane is exposed to incoming light during each frame interval. At 24fps, one frame occupies 1/24th of a second of real time. If the shutter is open for all of that interval, it captures the full 1/24s of motion occurring in the scene. In practice, mechanical film cameras used a rotating disc shutter that covered the film for part of each frame interval - the shutter angle described what fraction of the rotation the opening occupied. As RED's shutter angle tutorial explains, the shutter angle terminology has persisted as a universal way to describe the appearance of motion blur in video, even though current digital cameras do not necessarily control shutter speed with a physical rotating disc.

The 180-degree rule in cinematography holds that the shutter should be open for half the frame interval. At 24fps, 180 degrees gives a shutter speed of 1/48s. This produces the characteristic motion blur of cinematic footage: moving subjects have a blur arc that matches how human vision perceives motion, giving the image a natural, organic quality. Shutter speeds significantly faster than 180 degrees produce choppy, stroboscopic motion - the "Saving Private Ryan effect" - because the shutter captures motion in discrete, minimally blurred snapshots. Speeds significantly slower than 180 degrees produce excessive smearing and a ghostly quality. According to ARRI's white paper on the ALEXA Studio shutter, each time the shutter angle is halved, the exposure time is halved: at 25fps, 180 degrees gives 1/50s, while 90 degrees gives 1/100s.

Shutter speed's exposure role is secondary to aperture and ISO for most narrative production decisions. Because the 180-degree convention is so strong, DPs rarely change shutter speed to adjust exposure - they adjust aperture and ISO instead, using ND filters if necessary. Deliberate departures from 180 degrees are a stylistic choice with visible consequences on motion quality, not a casual exposure adjustment.

Historical Context & Origin

The rotating disc shutter of mechanical film cameras was a fixed physical component. Cinematographers changed effective shutter speed by swapping to a disc with a different opening angle. The 180-degree convention developed from a combination of practical and perceptual factors: it was mechanically convenient, and the 1/48s exposure at 24fps produced motion blur consistent with the temporal resolution of human visual perception. When digital cinema cameras replaced mechanical shutters with electronic ones, they retained the shutter angle convention as the standard way to set exposure time, preserving continuity with the film tradition. The ARRI ALEXA Studio is unique among digital cameras in offering both an electronic shutter and a physical mirror shutter, as documented in ARRI's white paper. The mirror shutter can reduce from 180 degrees to 11.2 degrees using a carbon blade behind the mirror, matching the mechanical control of a traditional film camera.

How It's Used in Practice

Scenario 1 - Standard Narrative (DP): The DP sets the ARRI ALEXA 35 to 24fps and 180-degree shutter throughout the production. All motion - walking, gestures, vehicle movement - reproduces with natural cinematic motion blur at 1/48s. The shutter setting is confirmed once and not revisited unless a specific scene requires a departure. The 1st AC verifies the setting on the FPS screen at the start of each shooting day.

Scenario 2 - Action / War (Director / DP): For a battle sequence, the director wants a desaturated, high-contrast, stroboscopic look reminiscent of Saving Private Ryan (1998). The DP sets the shutter to 45 degrees (1/192s at 24fps), dramatically reducing motion blur. Moving subjects stutter rather than blur. The effect is disturbing and visceral - clearly a departure from the film's normal visual grammar. The DP compensates for the 2-stop exposure loss by opening the aperture from T4 to T2.8 and adding a 2K HMI.

Scenario 3 - Slow Motion (DP): Shooting at 120fps for a slow-motion sequence on a Sony VENICE 2, the DP applies the 180-degree rule: 180 degrees at 120fps gives 1/240s. This preserves natural motion blur in the slow-motion playback. If the shutter were left at 1/48s while shooting 120fps, each frame would have 2.5x too much blur relative to the playback speed. The DP adds 4 stops of light (two 18K HMI fixtures) to compensate for the exposure loss at 1/240s.

Scenario 4 - Mains Power Sync (DP): Shooting under 50Hz HMI lights in the UK at 24fps, the DP sets the shutter to 172.8 degrees instead of 180 to avoid flicker. At 172.8 degrees and 24fps, the shutter speed is 1/50s, which syncs cleanly with the 50Hz mains power. In the US at 60Hz, 180 degrees at 24fps (1/48s) syncs with 60Hz mains without flicker.

Usage Examples in Sentences

"Keep the shutter at 180 throughout - I don't want any stroboscopic motion in this film."

"Drop the shutter to 45 degrees for the fight sequence - the stutter is the point."

"At 120fps you still want 180 degrees - calculate the corresponding shutter speed and set it before you roll."

"A slower shutter brightens the image and increases blur; a faster shutter darkens it and sharpens motion."

Common Confusions & Misuse

Shutter Speed vs. Shutter Angle: Shutter speed is a time value (1/48s). Shutter angle is a rotational value (180 degrees) that describes the fraction of the frame interval during which the shutter is open. The two are equivalent at a specific frame rate: 180 degrees at 24fps equals 1/48s. At 60fps, 180 degrees equals 1/120s. The shutter angle notation is preferred in cinema because it remains constant across frame rates - 180 degrees always means "half the frame interval" regardless of fps. Setting a fixed 1/48 shutter speed while changing frame rate produces very different motion blur at different frame rates, while 180 degrees always produces the same motion blur characteristics.

Shutter Speed vs. Frame Rate: Frame rate determines how many frames are captured per second. Shutter speed determines how long each frame is exposed. Changing the frame rate changes the duration of each frame interval and therefore the effective shutter speed at a given shutter angle. They are related but independent parameters. A common mistake is setting the shutter speed to match the frame rate exactly (1/24 at 24fps), which equals a 360-degree shutter angle and produces extreme motion blur unsuitable for most narrative work.

Variations by Context

Key People & Films

Janusz Kaminski ASC created the defining example of narrow shutter angle cinematography with Saving Private Ryan (1998), using a 45-degree to 90-degree shutter for the D-Day landing sequences. The staccato motion and reduced blur became instantly identifiable as a combat aesthetic. Roger Deakins used a 45-degree shutter on selected sequences in Sicario (2015) to create a tense, hyper-real quality during border convoy scenes. Emmanuel Lubezki used wide shutter angles (approaching 360 degrees) on selected sequences in The Revenant (2015) to maximise exposure in natural light, accepting the increased motion blur as part of the film's raw, immersive visual style. The ARRI ALEXA Studio's mirror shutter, the only physical rotating shutter on a digital cinema camera, was developed under the guidance of cinematographers who wanted the optical viewfinder and mechanical shutter feel of a film camera in a digital body.

Equipment / Tools Reference

The ARRI ALEXA 35, ALEXA Mini LF, and ALEXA Studio offer adjustable electronic shutter angles from 5 to 356 degrees (the ALEXA Studio additionally offers a mechanical mirror shutter from 11.2 to 180 degrees). The Sony VENICE 2 supports shutter angles from 11 to 356 degrees. The RED V-Raptor supports shutter angles from 2 degrees to 360 degrees. For calculating shutter speed from shutter angle, the Exposure / Shutter / Focal Length Calculator on this site follows the SMPTE standard formula: Shutter Speed = 1 / (FPS times (360 / Shutter Angle)). Light meters like the Sekonic L-858D Cinema and Gossen Starlite 2 read directly in shutter speed and can convert to shutter angle. The pCam Pro app calculates shutter speed and angle conversions on set.

Standards & Specifications

The SMPTE standard for timecode (SMPTE 12M) indirectly governs shutter speed by defining the frame interval that shutter angle references. The DCI specification requires 24fps or 48fps for 2D digital cinema, which fixes the standard shutter speed at 1/48s (180 degrees at 24fps) or 1/96s (180 degrees at 48fps). The SMPTE RIS OSVP metadata standard defines shutter angle as an integer in the range 0.01 to 360.00 degrees with 0.01-degree precision for VFX camera metadata. The 172.8-degree shutter angle at 24fps produces exactly 1/50s, which matches the standard shutter speed on most light meters and syncs with 50Hz mains power in PAL regions. At 24fps with 60Hz mains power, 180 degrees (1/48s) syncs without flicker.

Common Questions / FAQ

Q: What is the 180-degree shutter rule and why is it standard?

A: The 180-degree shutter rule sets the shutter open for half of each frame interval. At 24fps, this gives 1/48s exposure. It is standard because the resulting motion blur matches how human vision perceives motion - fast enough to avoid excessive smearing, slow enough to avoid stroboscopic stutter. Most narrative cinema worldwide uses this setting as the default.

Q: What shutter angle should I use for slow motion at 120fps?

A: Maintain 180 degrees. At 120fps, 180 degrees gives 1/240s, which preserves natural motion blur when played back at 24fps. If you keep the shutter speed at 1/48s instead of maintaining 180 degrees, each frame at 120fps would have 2.5x too much blur for the playback speed. You will need approximately 4 stops more light at 1/240s compared to 1/48s.

Q: Why do some DPs use 172.8 degrees instead of 180?

A: At 24fps, 172.8 degrees gives exactly 1/50s, which matches the standard shutter speed on most light meters and syncs cleanly with 50Hz mains power (used in PAL regions). Many DPs prefer it for the cleaner meter reading. The exposure difference between 172.8 and 180 degrees is negligible - about 1/6 of a stop.

Related Terms

• Aperture - The primary exposure control; shutter speed is adjusted alongside it
• ISO - Third exposure control; together with aperture and shutter speed forms the exposure triangle
• Frame Rate - Determines the frame interval that shutter angle translates into a shutter speed
• Exposure - The overall brightness result of aperture, shutter speed, and ISO combined
• Slow Motion - Requires recalculating shutter speed to maintain correct motion blur at high frame rates

See Also / Tools

The Exposure / Shutter / Focal Length Calculator calculates the correct exposure settings for any combination of aperture, shutter speed, and ISO, including shutter angle to shutter speed conversions. The Slow Motion Calculator shows the frame rate, shutter angle, and resulting playback speed for slow-motion sequences.