Shutter Angle vs. Shutter Speed: Which Should You Set on Your Camera?

The Frame Rate Change That Ruined the Motion Blur

A DP shoots a music video at 24fps with a shutter speed locked at 1/50s -- close enough to the 180-degree standard for 24fps that motion blur looks correct. Midway through the day, the director requests some 48fps overcranked inserts for a slow-motion sequence. The camera is handed back, the frame rate is changed to 48fps, and shooting continues. The 1/50s shutter speed remains unchanged because nobody noticed.

In post, the 48fps footage plays back at 24fps and looks hyperreal and clinical -- not the dreamy, slightly diffuse slow motion the director expected. At 1/50s and 48fps, the shutter angle is effectively 86 degrees, not 180. The motion blur is half of what it should be.

This post explains the relationship between shutter angle and shutter speed, how to convert between them, and when to use each unit to avoid this exact problem.

The conversion formula and practical values below follow the standard used by ARRI, RED, and SMPTE documentation for rotary shutter simulation in digital cinema cameras.

The Conversion Formula

Shutter angle originated with film cameras, which used a physical rotating disc with a pie-slice-shaped cut-out. The angle of the cut-out determined how long the film frame was exposed to light during each revolution. In digital cameras, shutter angle is simulated by the camera's electronic shutter timing.

The conversion between shutter angle and shutter speed is:

Shutter Speed (seconds) = Shutter Angle (degrees) / (360 x frame rate)

Equivalently:

Shutter Angle (degrees) = Shutter Speed (seconds) x 360 x frame rate

At 24fps and 180 degrees: Speed = 180 / (360 x 24) = 180 / 8,640 = 1/48s (cameras typically display this as 1/48 or round to 1/50)

At 25fps and 180 degrees: Speed = 180 / (360 x 25) = 180 / 9,000 = 1/50s (exact)

At 30fps and 180 degrees: Speed = 180 / (360 x 30) = 180 / 10,800 = 1/60s (exact)

At 48fps and 180 degrees: Speed = 180 / (360 x 48) = 180 / 17,280 = 1/96s

The critical insight: when you express the setting as a shutter angle (180 degrees) and change the frame rate, the camera automatically recalculates the correct shutter speed. When you express the setting as a shutter speed (1/50s) and change the frame rate, the speed stays fixed and the angle changes -- motion blur character changes with it.

Three Real-World Scenarios Where the Distinction Matters

Example 1: Music Video with Mixed Frame Rates, ARRI ALEXA Mini, 24fps and 48fps

A DP shoots a music video with performance sections at 24fps and motion-blur slow-motion inserts at 48fps. On the ARRI ALEXA Mini, the shutter is set as an angle: 180 degrees throughout. When the camera operator changes from 24fps to 48fps, the ALEXA automatically adjusts from 1/48s to 1/96s. The motion blur character of the 48fps footage, when played back at 24fps (2x slow motion), matches the aesthetic of the 24fps performance footage. No manual adjustment is needed.

Example 2: Commercial Director on Sony FX3, Locked at 1/50s for Flicker Safety

A commercial DP shoots in a location with fluorescent lighting on 50Hz mains (common in European and UK productions). The flicker-safe shutter speed is 1/50s. The DP sets the Sony FX3 to 1/50s at 25fps (exactly 180 degrees). When a 50fps slow-motion insert is required, they stay at 1/50s intentionally -- at 50fps this is 360 degrees (full-open shutter), eliminating motion blur entirely. The DP then uses the Flicker-Free Shutter Calculator to confirm that 1/100s (180 degrees at 50fps) is also flicker-free, and switches to 1/100s for a more filmic look on the slow-motion inserts.

Example 3: Documentary ENG Camera, Sony PXW-FX9, Variable Frame Rate Work

A documentary operator uses a Sony PXW-FX9 with the shutter set as a speed: 1/50s. The operator changes from 25fps interview coverage to 100fps slow-motion crowd coverage without updating the shutter. At 1/100s and 100fps, the shutter angle is exactly 180 degrees -- by coincidence, the motion blur is correct. But at 1/50s and 100fps, the shutter angle would be 360 degrees (no motion blur). The operator checks the Motion Blur Calculator to confirm the angle before any frame rate change, making it a standard part of their frame-rate-change workflow.

Shutter Angle to Shutter Speed Reference Table

The table below shows shutter speed equivalents for common shutter angles across five standard frame rates. Shutter speeds are rounded to the nearest standard value.

The 172.8-degree angle is a specific case common in NTSC broadcast: it gives exactly 1/50s at 24fps for flicker-safe shooting under European mains lighting. ARRI includes it as a preset on the ALEXA for this reason.

How to Set Shutter Correctly When Changing Frame Rates: Step by Step

Step 1: Decide whether your camera supports shutter angle natively. ARRI cameras (ALEXA, AMIRA, ALEXA 35), RED cameras (KOMODO, MONSTRO, V-RAPTOR), and some Sony Cinema Line cameras (VENICE 2, FX9) expose shutter as an angle setting in the menu. If shutter angle is available, use it.

Step 2: If your camera only shows shutter speed (most mirrorless bodies including Sony A7 series, Canon EOS R series, Fujifilm), calculate the target shutter speed using: Speed = Angle / (360 x fps). Apply the 180-degree rule: 1/(2 x fps) is your baseline.

Step 3: Before any frame rate change, recalculate the target shutter speed for the new frame rate. Use the Motion Blur Calculator to confirm both the old and new shutter speed values before touching the frame rate dial.

Step 4: For mixed frame-rate shoots (main frame rate plus overcranked inserts), write both shutter speeds on tape and stick it to the camera body or monitor. Call the shutter update as part of the frame-rate change announcement so the 1st AC and operator both confirm it.

Step 5: Verify flicker safety when changing shutter speed. If you are in a mixed-mains environment (50Hz or 60Hz fluorescent lighting), check that your new shutter speed is a multiple of the mains frequency. The Flicker-Free Shutter Calculator returns safe shutter speed options for any frame rate and mains frequency combination.

At the end of this process you have a confirmed shutter speed for each frame rate in use, verified before any frame rate change on set.

Pro Tips and Common Mistakes

Pro Tip: On ARRI ALEXA cameras, setting shutter as an angle and enabling Sync mode locks the shutter to the set angle across any frame rate change. The camera adjusts the actual exposure time automatically. This is the correct workflow for any production where frame rate will change during the day -- the motion blur character is preserved without any manual recalculation.

Pro Tip: The 180-degree rule produces a specific look: motion blur where moving objects travel approximately one frame-width of blur per frame at normal subject velocities. This is the standard for narrative cinema because it matches the motion blur of 35mm film at 24fps through a 180-degree shutter. Departing from 180 degrees is a creative choice -- 90 degrees gives a crisper, more strobed look; 360 degrees produces heavy, painterly blur. Both are used intentionally in narrative work, but 180 is the default baseline.

Pro Tip: On Sony FX-series cameras, the S&Q (Slow and Quick) motion mode uses a separate shutter setting from the main camera mode. When you enter S&Q mode, the shutter setting does not carry over from your main shooting mode. Confirm the shutter setting manually every time you switch into S&Q -- leaving the default (often 1/250s) active in S&Q mode while expecting 180-degree blur is one of the most common errors on Sony-based productions.

Common Mistake: Treating shutter angle as a fixed number that applies across all frame rates on a shutter-speed camera. A 1/50s shutter is 180 degrees at 25fps, 216 degrees at 24fps, and 360 degrees at 50fps. If you think of the setting as "I always shoot 180 degrees," you must recalculate the speed number every time the frame rate changes. The fix: use a camera that supports native shutter angle, or keep the Motion Blur Calculator open on a phone during frame rate transitions.

Common Mistake: Not accounting for the 24fps/25fps distinction in international productions. On a co-production shooting in a 60Hz country (USA) at 24fps, 1/48s is the 180-degree shutter. On the same production shooting in a 50Hz country (UK) at 25fps, 1/50s is 180 degrees. Swapping the shutter speed without adjusting for the frame rate difference changes the motion blur slightly. Use the Flicker-Free Shutter Calculator to identify safe shutter speeds that are simultaneously flicker-free and close to 180 degrees for each shooting territory.

Frequently Asked Questions

Why do some cinema cameras show shutter angle and others show shutter speed?

Cameras designed as dedicated cinema tools (ARRI, RED) use shutter angle because it is the natural unit for cinematographers trained on film and because it preserves motion blur intent across frame rate changes without recalculation. Mirrorless and DSLR-derived cameras borrowed their shutter interfaces from still photography, where shutter speed (seconds or fractions) is the standard unit. Neither is more accurate -- they describe the same physical exposure duration using different coordinate systems.

What is 172.8 degrees and why is it on ARRI camera presets?

172.8 degrees is a specific shutter angle that produces exactly 1/50s exposure time at 24fps. Because 50Hz mains power is the standard in Europe, a 1/50s shutter speed is flicker-safe for fluorescent and HMI lighting on that power grid. The 172.8-degree preset allows ARRI cameras shooting 24fps in Europe to maintain near-180-degree motion blur while staying flicker-safe. The visual difference from true 180 degrees is negligible -- the flicker safety benefit is real.

Does shutter angle affect exposure in the same way as shutter speed?

Yes, directly. A 180-degree shutter allows light to hit the sensor for exactly half of each frame cycle. A 90-degree shutter allows light for a quarter of the cycle. Going from 180 degrees to 90 degrees reduces exposure by one stop. Going from 180 degrees to 360 degrees increases exposure by one stop. The relationship between shutter angle and exposure is linear and follows the same inverse relationship as shutter speed.

When is it acceptable to shoot outside the 180-degree range?

Deliberately shooting at 90 degrees or tighter (1/96s to 1/200s at 24fps) is common in action sequences, sports, and music videos where a strobed, hyperreal look is desired. Horror and thriller genres sometimes use 45-degree shutters to create disorienting, staccato motion. Wide-open shutters (270 to 360 degrees) appear in stylised sequences that want to emphasise motion blur as an expressive element. The 180-degree standard is a baseline for naturalistic narrative, not a rule that applies across all genres.

Related Tools

The Motion Blur Calculator converts between shutter angle and shutter speed for any frame rate and shows the resulting motion blur duration in milliseconds. The Flicker-Free Shutter Calculator returns safe shutter speeds for any frame rate and mains frequency combination -- essential when setting shutter speeds on location.

For understanding how shutter speed interacts with the rest of the exposure triangle, Exposure Triangle for Cinematographers covers aperture, ISO, and shutter as an integrated system. For frame rate decisions and their effect on the final look, Frame Rates in Filmmaking covers the full range from 24fps to 120fps with production context.

One Unit for Both Situations

Shutter angle and shutter speed describe the same setting. The difference is that shutter angle stays correct when the frame rate changes because it is defined relative to the frame cycle, not as an absolute time value. On a camera that supports it, always set shutter as an angle. On a camera that only offers shutter speed, use the formula -- or the Motion Blur Calculator -- to recalculate the correct speed every time the frame rate changes. The 30 seconds this takes before a frame rate transition is significantly cheaper than discovering the error in post.

This post covers standard progressive-scan digital cinema and mirrorless cameras. Interlaced formats and HDR high-frame-rate production involve additional shutter considerations worth a dedicated treatment. What frame rate transitions have caught you out on set -- and was the camera set to angle or speed when it happened?