How does the 1/focal-length rule work to avoid camera shake?

The rule says that to shoot handheld without camera shake, your shutter speed should be at least **1 over the focal length** in use. At 50 mm, don't drop below **1/50 s**; at 200 mm, **1/200 s** minimum. On an APS-C sensor, multiply the focal length by 1.5 (so 200 mm becomes 300 mm equivalent, i.e. 1/300 s). It's a baseline, not a guarantee: if you're shaky, take a safety margin (1/2× the focal length). Optical or IBIS stabilization buys 2 to 4 stops, but it only corrects your shake — never the subject's motion.

What shutter speed for silky water?

To turn a waterfall or river into a milky veil, aim for **1/4 s to 2 s** depending on flow. Fast-charging water: **1/4 s to 1/2 s** is enough. Calm trickles or coastal swells: **1 s to 4 s**. For a perfectly smoothed sea in fog mode, climb to **30 s to several minutes** with an **ND 10-stop filter**. Tripod essential, remote release or 2-second self-timer to avoid vibration, ISO 100, aperture f/11 to f/16 to extend the exposure. In broad daylight, without an ND filter, you'll never reach those speeds without overexposing.

What shutter speed for smooth Reels or vertical videos?

In video, the convention is the **180° rule**: your shutter speed should be roughly **double your frame rate**. At 25 fps, set **1/50 s**; at 30 fps, **1/60 s**; at 60 fps, **1/125 s**. This rule produces a natural motion blur that resembles what the human eye sees. A speed too fast (1/500 s at 25 fps) gives a stuttering, clinical render à la *Saving Private Ryan*. Too slow, and it's mush. In bright sun, a **variable ND filter** lets you hold the rule without overexposing.

EXIF Data

Shutter Speed

Shutter speed is the time you grant light to register on the sensor. A fraction of a second that decides whether the world freezes or starts to dance.

Photo : Mike Lewis HeadSmart Media / Unsplash

Definition

What is shutter speed?

Shutter speed is the length of time the shutter stays open to expose the sensor (or film) to light. It's measured in seconds or, more often, fractions of a second: 1/8000 s, 1/4000 s, 1/2000 s, 1/1000 s, 1/500 s, 1/250 s, 1/125 s, 1/60 s, 1/30 s, 1/15 s, 1/8 s, 1/4 s, 1/2 s, 1 s, 2 s, ... up to 30 s and beyond in Bulb mode. Each step doubles or halves the amount of light received — the language of the exposure triangle.

Its visual effect runs in two directions. A fast speed freezes motion: the suspended drop, the runner stopped mid-stride. A slow speed fluidifies it: light trails, silky water, a ghostly crowd. The rule of thumb 1/focal length (with a 200 mm, don't drop below 1/200 s handheld) protects against camera shake but says nothing about subject motion.

Two families of shutters coexist: the focal-plane type (most DSLRs and mirrorless bodies), fast but capped by the flash X-sync at ~1/200 s, and the leaf shutter (in some lenses), which syncs at every speed. Eadweard Muybridge invented this vocabulary in 1878 by freezing a galloping horse; Henri Cartier-Bresson turned it into a philosophy with the decisive moment.

Example

In practice

Three scenarios tell almost everything shutter speed knows how to do.

Sport, at 1/2000 s. You're shooting a basketball game or a surfer. Subject moves fast, you want every drop of water, every fold of the jersey, perfectly sharp. Climb to 1/2000 s or 1/4000 s, open to f/2.8 or f/4 to keep ISO reasonable, and shoot bursts. Eye sharpness is non-negotiable: if it slips, the image is dead, no matter the composition.

Waterfall, at 1/4 s on a tripod. You want that dreamy white veil draping over the rocks. Shutter priority, 1/4 s to 1 s, ISO 100, aperture f/11 or f/16, tripod required with remote release or 2-second self-timer. If daylight forces you slower still, an ND filter (neutral density) is your best friend. The slow gesture writes time into matter.

Sport panning, at 1/30 s. The cyclist passes at full speed, you follow at the same pace and trigger at 1/30 s or 1/60 s. The subject stays sharp, the background streaks horizontally: pure sense of speed. Stabilizer in panning mode if available.

Shutter speed never lives alone: it dialogues with aperture, ISO, and the available light in the exposure triangle. Move one slider and you always move another.

Common mistakes

What we see too often

1/60 s at 200 mm focal length. The classic beginner move — believing stabilization works miracles. At 200 mm full-frame equivalent, dropping below 1/200 s handheld (ideally 1/250 s or 1/400 s for margin) all but guarantees camera shake. The photo looks softly sharp on the back screen, then collapses at full enlargement. IBIS or OIS stabilization buys 2 to 4 stops, no more, and never corrects subject motion.

1/1000 s that flatlines movement. Freezing everything isn't always right. A dancer at 1/1000 s becomes a statue: technically sharp, emotionally dead. A slight trail at 1/250 s on the arms gives the feeling of the gesture, tells a story. Over-freezing is betraying the subject through excess of cleanliness. The right speed is the one that preserves the soul of the motion while keeping the face readable.

Forgetting flash sync. You climb to 1/2000 s in studio with a brand-name flash: black band across the image, sensor half-occluded. The X-sync (~1/200 s) is a wall. To go beyond, you need a compatible HSS (High Speed Sync) mode, which pulses the flash continuously but bleeds enormous power. Otherwise, stay at 1/200 s or slower and compensate via aperture or ND filters.

How Focalis evaluates

How Focalis evaluates shutter speed

Focalis-X reads the shutter speed from the EXIF data and cross-checks it against the subject detected in the image. Blurry sports photo at 1/60 s? The analysis flags the underdose. Waterfall sharp as a stone at 1/500 s? Suggestion to slow down and capture the motion. The engine looks for camera-shake clues (faint trails, double sharpness), evaluates coherence with the focal length and the subject, and proposes a speed range matched to the probable intent. The 1/focal-length rule is checked automatically. Analyze a photo →

FAQ

Frequently asked questions

How does the 1/focal-length rule work to avoid camera shake?
The rule says that to shoot handheld without camera shake, your shutter speed should be at least 1 over the focal length in use. At 50 mm, don't drop below 1/50 s; at 200 mm, 1/200 s minimum. On an APS-C sensor, multiply the focal length by 1.5 (so 200 mm becomes 300 mm equivalent, i.e. 1/300 s). It's a baseline, not a guarantee: if you're shaky, take a safety margin (1/2× the focal length). Optical or IBIS stabilization buys 2 to 4 stops, but it only corrects your shake — never the subject's motion.
What shutter speed for silky water?
To turn a waterfall or river into a milky veil, aim for 1/4 s to 2 s depending on flow. Fast-charging water: 1/4 s to 1/2 s is enough. Calm trickles or coastal swells: 1 s to 4 s. For a perfectly smoothed sea in fog mode, climb to 30 s to several minutes with an ND 10-stop filter. Tripod essential, remote release or 2-second self-timer to avoid vibration, ISO 100, aperture f/11 to f/16 to extend the exposure. In broad daylight, without an ND filter, you'll never reach those speeds without overexposing.
What shutter speed for smooth Reels or vertical videos?
In video, the convention is the 180° rule: your shutter speed should be roughly double your frame rate. At 25 fps, set 1/50 s; at 30 fps, 1/60 s; at 60 fps, 1/125 s. This rule produces a natural motion blur that resembles what the human eye sees. A speed too fast (1/500 s at 25 fps) gives a stuttering, clinical render à la Saving Private Ryan. Too slow, and it's mush. In bright sun, a variable ND filter lets you hold the rule without overexposing.