Shutter Speed Calculator

Background.

This shutter speed calculator answers one question: how fast does the shutter have to be for this picture to be sharp? It is not an exposure calculator. Nothing here is a light level and nothing here is an EV — if you want to know how much light a given aperture, shutter and ISO collect, the exposure value calculator is the page you want. This one is about blur.

There are two entirely separate ways a photograph goes soft, and confusing them is the most common reason people dial in a shutter speed that does not work. The first is camera shake: your hands move, and because the lens projects an angle onto the sensor, that tremor smears across the frame in proportion to the focal length. The second is subject motion: the subject moves, and its image sweeps across the sensor at a speed set by the magnification, which depends on the focal length and the distance. These two limits scale with different things, they respond to different fixes, and only one of them can be helped by image stabilisation.

That last point is worth being blunt about, because marketing copy rarely is. CIPA, the industry body whose logo appears on the stabilisation claims printed on every lens box, defines the scope of its own standard in clause 3-1-2: image stabilisation "can be further classified into handheld blur correction and motion blur correction", and the standard "excludes applications for motion blur correction". A lens rated at five stops buys you five stops against your own hands. It buys you exactly nothing against a running child. This calculator shows both limits side by side, in every mode, so you can see at a glance which one is the constraint you actually have to solve.

The camera-shake side is the familiar reciprocal rule — shoot no slower than one over the 35 mm-equivalent focal length — with stabilisation stops applied on top. It is folklore with a physical skeleton, not a measured standard, and this page says so rather than dressing it up. The subject-motion side is real geometry: transverse magnification m = f/(u − f) turns ground speed into image speed, and dividing your accepted blur by that image speed gives the longest exposure you can get away with. Because you choose the blur tolerance yourself, the answer is honest about being a tolerance rather than a physical constant, and the page tells you how to pick one instead of hiding a circle-of-confusion convention in the code.

Below the widget you will find the two equations written out, a worked example computed by hand for a 200 mm lens on an APS-C body photographing a runner, the reason a subject travelling toward you is so much easier to freeze than one crossing the frame, why the marked speeds on a camera dial are not the numbers they claim to be, and an honest list of everything this model leaves out — rolling-shutter skew, shutter efficiency, the fact that a sprinter's hand moves several times faster than the sprinter, and the enormous variation in hand tremor between people and postures.

What is shutter speed calculator?

Shutter speed is the length of time the sensor or film is exposed to the image, and for sharpness purposes it is a race between two smears. Camera shake produces an angular smear: if your hand rotates the camera through a small angle θ during the exposure, the image displaces by roughly f·θ on the sensor, so a longer lens magnifies your tremor in direct proportion. That is the entire physical content of the reciprocal rule — the rule fixes a tolerable θ implicitly and says t ∝ 1/f. It was calibrated in the 35 mm film era for prints of a modest size, so on a crop sensor you multiply the focal length by the crop factor first, and on a high-resolution body inspected at 100 % it is optimistic. Image stabilisation moves either a lens group or the sensor to cancel that angular motion, and CIPA DC-X011 measures the benefit on a certified shaker table, expressing it in stops: one stop is one step in the APEX TV scale, which the standard illustrates as the difference between 1/1000 s (TV10) and 1/500 s (TV9). Each stop therefore doubles the exposure time you can hand-hold. Subject motion is a different geometry entirely. The subject's image moves across the sensor at v·m·sin φ, where v is the ground speed, m = f/(u − f) is the thin-lens transverse magnification and φ is the angle between the direction of travel and the optical axis. Only the perpendicular component smears, which is why a bird flying straight at the lens can be frozen at a shutter speed that would badly blur the same bird crossing the frame. Requiring the smear to stay inside an accepted blur diameter b gives t = b/(v·m·sin φ). Neither limit is a standard. ISO 516:2019 is the standard that governs shutters, and what it standardises is the timing: it "specifies the exposure-time markings for all types of shutters and their tolerances", covering shutters that "affect the control of exposure, motion-stopping ability and synchronization with a photoflash light source". It tells you what 1/500 on the dial is allowed to mean; it does not tell you when 1/500 is fast enough.

How to use this calculator.

1. 01Choose what has to be sharp. Leave it on Both unless you are on a tripod (choose subject motion only) or your subject is genuinely stationary (choose camera shake only). Both limits are displayed either way — the dropdown only decides which one becomes the headline recommendation.
2. 02Enter the focal length engraved on the lens in millimetres, then your sensor's crop factor separately. Do not enter a 35 mm-equivalent focal length: the crop factor field already accounts for the format, and entering an equivalent would apply the multiplier twice.
3. 03Enter the CIPA-rated stops of stabilisation for your body-and-lens combination, or 0 if there is none. Manufacturers publish this figure; it is measured on a shaker table under laboratory conditions, so treating the claim as an upper bound and entering a stop less is a defensible habit.
4. 04Describe the subject's movement: its ground speed and unit, how far away it is in metres, and the direction it is travelling relative to your lens axis. The direction matters more than most people expect — switching from across-the-frame to 45° buys you a full half-stop.
5. 05Set the blur you will accept, measured on the sensor. 0.03 mm is about five pixels on a 24 MP full-frame sensor and is a sensible default for prints and screen viewing. Halve it if you intend to inspect the file at 100 % or print large.
6. 06Read the headline recommendation, then read the "what is costing you speed" line underneath it. If subject motion is binding, a tripod and a stabilised lens will not save the shot — you need a faster shutter, which means a wider aperture or more ISO. If camera shake is binding, support is the cheapest fix available.
7. 07Dial in the marked speed the calculator suggests. It always rounds toward the faster marked speed, never the slower one, so the shot stays inside the tolerance you set rather than one stop outside it.
8. 08Treat every number here as a planning figure with a wide tolerance. Hand tremor varies enormously between people, postures and states of caffeination, and a runner's hands and feet move several times faster than the runner's centre of mass.

The formula.

Work in millimetres and seconds throughout.

Camera shake first:

t_shake = (1 / (f × c)) × 2^s

The 1/(f × c) term is the reciprocal rule: the 35 mm-equivalent focal length in the denominator, the tolerable exposure time in seconds. Its justification is the angular-smear argument — for a fixed hand-tremor angle θ, the displacement on the sensor is f·θ, so the tolerable time falls as 1/f — and nothing more. It is a rule of thumb, not a standard, and it was calibrated for film-era output sizes.

The 2^s term is the part that is formally defined. CIPA DC-X011-2024 §3-1-9 reads: "According to APEX expressions, the difference in TV values is represented in 'stops.' For instance, the difference between shutter speeds of 1/1000 (TV10) and 1/500 seconds (TV9) or that between shutter speeds of 1/125 (TV7) and 1/60 seconds (TV6) accounts for one stop." One stop is one doubling of exposure time, so s stops multiply the tolerable time by 2^s. Three stops turn 1/300 s into 1/37.5 s, a factor of exactly eight.

Subject motion next. The thin-lens transverse magnification of an object at distance u is

m = f / (u − f)

and the image of a subject moving at ground speed v travels across the sensor at v·m·sin φ, where φ is the angle between the direction of travel and the optical axis. Requiring that smear to stay inside an accepted blur diameter b gives

t_motion = b / (v × m × sin φ)

The three offered directions use sin 90° = 1, sin 45° = 0.70711 and sin 15° = 0.25882. There is deliberately no 0° option: a subject moving exactly along the optical axis has no transverse component at all and the tolerable time would be infinite, which is a mathematical artefact rather than photographic advice.

The blur tolerance b is a choice, not a constant. The default 0.03 mm is about five pixels on a 24 MP full-frame sensor with a 5.9 µm pixel pitch. Halving it halves the tolerable exposure time, exactly and linearly — which is the honest reason two shutter-speed calculators can disagree by a stop while both being internally correct.

Finally, the recommendation. In "both" mode it is min(t_shake, t_motion), because a photograph has to satisfy both constraints simultaneously; the other two modes simply report one of them. The marked speed is then the slowest value in the printed dial series — 1/8000, 1/4000, 1/2000, 1/1000, 1/500, 1/250, 1/125, 1/60, 1/30, 1/15, 1/8, 1/4, 1/2, 1, 2, 4, 8, 15, 30 s — that is still no slower than the recommendation. Rounding always goes toward the faster speed. Those markings are nominal rather than exact: the true geometric series doubles each time, so a dial marked 1/125 is 1/128 s and one marked 1/60 is 1/64 s. ISO 516:2019 is the standard that fixes shutter markings and their tolerances.

What the model leaves out: rolling-shutter skew, which distorts fast lateral motion rather than blurring it; shutter efficiency, the difference between the marked time and the effective time on a focal-plane shutter; the fact that a running subject's extremities move several times faster than its centre of mass, so a shutter speed that freezes the torso will still smear the hands; and panning, which deliberately trades background sharpness for subject sharpness and inverts the whole calculation.

A worked example.

Frequently asked questions.

References& sources.

1. [1]Camera & Imaging Products Association (2024). CIPA DC-X011-2024, Measurement and Description Method for Image Stabilization Performance of Digital Cameras (Optical System). Clause 3-1-9 defines the stop used by this calculator's 2^s term: 'According to APEX expressions, the difference in TV values is represented in "stops." For instance, the difference between shutter speeds of 1/1000 (TV10) and 1/500 seconds (TV9) or that between shutter speeds of 1/125 (TV7) and 1/60 seconds (TV6) accounts for one stop.' Clause 3-1-2 is the basis for the page's statement that stabilisation does nothing for a moving subject: 'while image stabilization can be further classified into handheld blur correction and motion blur correction, this standard excludes applications for motion blur correction.'
2. [2]International Organization for Standardization (2019). ISO 516:2019, Camera shutters — Timing — General definition and mechanical shutter measurements. The standard that governs shutter markings and their tolerances: it 'specifies the exposure-time markings for all types of shutters and their tolerances' and covers mechanical shutters that 'affect the control of exposure, motion-stopping ability and synchronization with a photoflash light source'. Cited for the marked dial series and for the fact that printed markings are nominal.
3. [3]National Institute of Standards and Technology. NIST Special Publication 811, Appendix B.9, Factors for Units Listed Alphabetically. Gives 'mile per hour (mi/h) → meter per second (m/s): 4.4704 E-01' as an exact factor, and 'inch (in) → meter (m): 2.54 E-02' exactly. These are the speed conversions used by the mph and km/h options.
4. [4]Nikon Corporation. D7500 Online Manual, Technical Notes — Specifications. Source for the crop-factor guidance in the input hint: the DX format sensor is '23.5 × 15.7 mm CMOS' and 'focal length in 35 mm [135] format equivalent to approx. 1.5× that of lenses with FX format angle of view'.
5. [5]International Organization for Standardization (2019). ISO 12232:2019, Photography — Digital still cameras — Determination of exposure index, ISO speed ratings, standard output sensitivity, and recommended exposure index. Cited for the ISO-speed framework behind the page's advice to buy shutter speed with sensitivity when the subject-motion limit is the binding constraint.