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Shutter Speed Calculator

Shutter speed controls how long your camera's sensor is exposed to light, directly impacting image brightness and motion blur. Photographers use this calculator to balance exposure across different lighting scenarios—from bright daylight to dim starfields—by inputting aperture, ISO, and light conditions. Understanding the relationship between these three exposure variables lets you freeze fast action or intentionally blur movement.

Last updated: April 25, 2026

Creators Jasmine J. Mah, BSc

Reviewers Krishna Nelaturu and Mateusz Mucha

1,483 people find this calculator helpful

Understanding Shutter Speed

Shutter speed refers to the duration the camera's shutter remains open, measured in fractions of a second or full seconds. A speed of 1/1000 means the shutter opens and closes in one-thousandth of a second; a speed of 2 seconds means a two-second exposure. This single variable profoundly affects both the amount of light reaching your sensor and how motion appears in your final image.

Fast speeds (1/500 or faster) admit minimal light and freeze moving subjects sharply.
Moderate speeds (1/60 to 1/125) suit handheld shooting in daylight without noticeable shake.
Slow speeds (1 second to several minutes) gather more light and blur motion, essential for night photography or creative effects.

The Exposure Triangle: Shutter Speed, Aperture, and ISO

Exposure is governed by three interdependent settings. Shutter speed determines how long light enters; aperture (f-number) controls the opening size; ISO sensitivity amplifies the sensor's response. Adjusting one requires compensating with the others to maintain correct exposure. For example, if you increase ISO from 100 to 400, you can use a faster shutter speed or smaller aperture to avoid overexposure.

Photographers often prioritize one element based on their creative intent. Portrait shooters may prioritize wide apertures for shallow depth of field, then adjust shutter and ISO accordingly. Sports photographers prioritize fast shutter speeds to freeze action, sacrificing depth of field or accepting higher ISO noise.

Shutter Speed Calculation

The shutter speed formula derives from the exposure value system, which standardises how light, aperture, and sensitivity interact. Rearranging the exposure equation yields a practical formula for determining the duration needed:

Shutter Speed (seconds) = (100 × aperture²) ÷ (ISO × 2^EV)

aperture — The f-number (e.g., 2.8 for f/2.8); larger apertures have smaller numbers.
ISO — Sensor sensitivity; higher values capture more light but introduce grain.
EV — Exposure value; represents the combined effect of light intensity (negative values for dim scenes, positive for bright).

Practical Example: Milky Way Photography

Suppose you're photographing the Milky Way with a camera maxing out at ISO 6400 and a lens with f/2.8 maximum aperture. The night sky typically measures around EV −7. Plugging these values into the formula:

Shutter Speed = (100 × 2.8²) ÷ (6400 × 2^(−7)) = 784 ÷ 50 ≈ 15.7 seconds

This result—roughly 16 seconds—gives adequate exposure for deep-sky imaging without excessive star trailing. Adjusting aperture wider (if available) or dropping ISO would lengthen the exposure further; narrowing the aperture or raising ISO would shorten it.

Critical Considerations for Shutter Speed

Several practical factors influence your shutter speed choice beyond the formula alone.

Handheld Camera Shake Threshold — The traditional rule—use a shutter speed faster than 1/(focal length in mm)—helps prevent blur from hand tremor. With a 50 mm lens, aim for at least 1/50 second when shooting handheld. Telephoto lenses require faster speeds; wider lenses tolerate slower ones. Image stabilisation can extend these limits by 2–4 stops.
Motion Blur and Subject Movement — Even a correctly exposed handheld shot blurs if your subject moves during exposure. Fast-moving subjects (running athletes, vehicles) demand shutter speeds of 1/500 or faster. Slower shutter speeds intentionally capture motion blur for creative effect—waterfalls, light trails, or crowds become painterly.
Noise vs. Exposure Trade-Off — Raising ISO to permit faster shutter speeds introduces visible grain, especially in shadow areas. In low light, you sometimes must accept higher ISO noise to avoid unmanageably slow shutter speeds that risk camera shake. Modern sensors perform better than older ones; test your own camera's noise tolerance.
Reciprocal Relationships and Real-World Limits — If your calculation yields 30 seconds but your camera's maximum shutter speed is 25 seconds, you must increase ISO or open the aperture further—if either option remains available. Many cameras cap out at 30 seconds; bulb mode (held open indefinitely) requires a remote trigger and introduces its own challenges.

Frequently Asked Questions

Why does a faster shutter speed result in a darker image?

A faster shutter speed (e.g., 1/2000 second) opens and closes quickly, admitting less light. Slower speeds (e.g., 2 seconds) hold the shutter open longer, gathering more light and producing brighter images. If you increase shutter speed without adjusting aperture or ISO, your image will underexpose. The formula shows this inverse relationship: faster shutter speed requires either wider aperture, higher ISO, or brighter lighting to maintain the same exposure.

What is the difference between shutter speed and shutter angle?

Shutter speed (measured in seconds or fractions thereof) is the absolute duration the sensor is exposed. Shutter angle applies primarily to cinema cameras and refers to the mechanical angle of a rotating shutter; it's a legacy concept less relevant to modern still photography. For handheld or DSLR/mirrorless photography, shutter speed is the standard metric.

Can I use a slow shutter speed in bright sunlight?

Not without reducing exposure elsewhere. Bright conditions produce high exposure values (EV 15+), which the formula translates to extremely fast shutter speeds. Attempting 2 seconds in direct sunlight would require closing the aperture to f/32 or dropping ISO to 50—neither practical on most cameras. Neutral density filters (dark optical panes) reduce light without changing colour, letting you use slow speeds creatively even in daylight.

How does autofocus affect shutter speed choice?

Autofocus operation occurs before the sensor exposes, so it doesn't directly consume shutter time. However, in low light, autofocus may hunt (refocus repeatedly) if shutter speed is too slow for the available light. Ensuring fast enough shutter for adequate sensor brightness (typically 1/30 or faster) helps autofocus lock reliably. Manual focus in very dim conditions bypasses this concern entirely.

Why would I deliberately use a slow shutter speed?

Slow shutter speeds serve creative and practical purposes beyond gathering light. Deliberate motion blur conveys speed and energy in sports or action shots. Long exposures of flowing water create a smooth, ethereal effect. Light painting—moving an LED or flashlight during a long exposure—writes with light directly onto the image. Star trails and Milky Way shots require seconds-long exposures to gather sufficient starlight and reveal galactic detail.

What happens if my calculated shutter speed is longer than my camera allows?

Many cameras limit exposures to 30 seconds (or bulb mode for indefinite exposure). If your calculation exceeds this limit, you must increase ISO, open the aperture wider, or add a light source (supplemental flash or continuous lighting). In astrophotography, if no adjustments help, bulb mode with a remote trigger or intervalometer allows you to exceed the camera's standard maximum and gather the long exposure needed.

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