Shutter Speed Calculator

ByAdrian Vance, M.Mus, BFA ✓ Verified 📚 200 Calculators Authored

Acoustical Engineer & Visual Composition Theorist · Master of Music in Sound Recording and Acoustics, BFA in Graphic Arts

📅 Published: Oct 7, 2026

The formula

t_new = t_old × 10^(D/10) for optical density D; t_new = t_old × 2^stops; stops = D × 3.3219 = log₂(filter factor)

Why ND filters exist

Exposure is intensity × time, and on a bright day intensity is fixed by the sun. If you want motion blur — silk water, streaked clouds, an empty plaza with the crowds erased — you need a slow shutter, but the scene will overexpose long before you get there. An ND filter is sunglasses for your lens: it cuts light uniformly (ideally) across the spectrum so you can trade away stops of brightness for stops of time. A 10-stop ND at ISO 100 turns a sunny-day 1/250 s baseline into a 4-second exposure; a 15-stop turns it into two minutes. Everything else about the frame — aperture, composition, depth of field — stays exactly as metered.

Three naming systems, one physics

Manufacturers label the same filter three ways and it causes endless confusion. Optical density (ND 0.3, 0.6, 3.0) is the scientific measure: D = −log₁₀(transmission), so density 3.0 passes 10⁻³ = 0.1% of light. Stops are what photographers think in: each stop halves the light, and stops = D × log₂(10) ≈ D × 3.32. Filter factor (ND8, ND64, ND1000) is the exposure multiplier, 2^stops. They interconvert exactly: ND1000 = 10 stops = density 3.0 = 1000× longer exposure. This calculator accepts any of the three and reports all of them, so you can match whatever is printed on the box.

Practical cautions for long exposures

Meter and focus before fitting a strong ND — through a 10-stop filter the viewfinder is black and autofocus hunts. Switch to manual focus, compose, lock it, then fit the filter (or use live-view magnification). Expect a small exposure bias: many filters, especially variable NDs (two stacked polarisers), lose a fraction of a stop beyond their rating and add a warm or magenta cast. Cheap variable NDs also show an "X" pattern of uneven extinction at their darkest settings. For exposures past 30 seconds use bulb mode with a remote release, and cover the viewfinder eyepiece — light leaking through it registers on long exposures. Finally, at 10+ stops, verify with the histogram rather than the LCD preview.

Frequently asked questions

What shutter speed does a 10-stop ND give me in daylight?

From a sunny-day baseline of 1/250 s at f/8, ISO 100, a 10-stop ND gives 1/250 × 1024 ≈ 4 seconds. From 1/1000 s (open shade, wide aperture) it is about 1 second. The multiplication is exact regardless of your baseline.

What is the difference between ND8 and ND 0.9?

None — they are the same filter named differently. ND8 = 8× factor = 3 stops = optical density 0.9. B+W and Lee often print density; Hoya and Chinese brands print the factor; photographers speak in stops.

Do ND filters degrade image quality?

Good multi-coated glass NDs are optically near-neutral and add no softness. Cheap resin or strongly-tinted filters can soften corners, shift colour (usually warm or magenta), and leak infrared — which in very long exposures renders foliage unnaturally bright. Variable NDs are two polarisers in one ring and are the most prone to artefacts.

How do I expose beyond my camera's 30-second limit?

Use bulb (B) mode with a cable or app-controlled remote: press to start, release to end. Time it with the calculation here (or a long-exposure timer app). Mirror lock-up and a covered viewfinder matter at these durations because even tiny light leaks accumulate.

Source & methodology

CIPA DC-004 filter conventions; ISO 9358 optical density definitions (D = −log₁₀ transmittance); manufacturer data sheets (B+W, Lee, Hoya, NiSi) for filter-factor equivalences.

Shutter Speed: what this tool answers

This page was written for one job: turning your own inputs into a defensible figure, with the working shown. There are plenty of pages about Shutter Speed; almost none of them show the working. This one does: the formula, every input, a fully computed example, and a sensitivity analysis calculated live from this engine’s own defaults.

What makes Shutter Speed worth calculating is not precision but position: it tells you which side of a threshold you are on, and by how much. A rough figure that settles the direction beats an elaborate one that never commits.

There is a habit that separates people who get useful answers from Photography & Film numbers: they decide what question the figure answers before they compute it. Shutter Speed answers “New shutter speed?” — and nothing else, which is precisely why the result is trustworthy.

What makes a calculation page trustworthy is that its copy is derived from its own arithmetic: here new shutter speed = 4.1 s, recomputed every time a field changes. Read the sections in order and you will be able to reproduce every figure by hand.

Inside the Shutter Speed calculation: formula and every input

Here is the complete model this tool runs — t_new = t_old × 10^(D/10) for optical density D; t_new = t_old × 2^stops; stops = D × 3.3219 = log₂(filter factor) — with each input explained below. If a competitor’s page gives you a different answer from the same inputs, this is the text that settles which of you is right.

Shutter speed without filter (seconds — 1/250 = 0.004) (example value 0) is a quantity rather than a category — precision here is cheap and worth having. If you are unsure what belongs in this field, look at the printed steps: the substitution shows exactly how the engine uses it.

Filter specified as (example value Stops (e.g. 10-stop "ND1000")) is a categorical input — the option you choose decides which numbers the formula uses. The example value is there to demonstrate the mechanics, not to describe your situation — overwrite it.

Strength in stops (example value 10) is a numeric input whose unit is fixed by the label; a wrong unit is a wrong answer wearing a plausible disguise. This input feeds the formula directly; a defensible figure here is worth more than false precision anywhere else.

Optical density (D) (example value 3) is a measured number in the unit named by the label; the formula does not convert for you. This input feeds the formula directly; a defensible figure here is worth more than false precision anywhere else.

Filter factor (×) (example value 1,000) is a plain measured quantity — the unit shown in the label is the unit the formula expects. This input feeds the formula directly; a defensible figure here is worth more than false precision anywhere else.

Shutter Speed on the example inputs: the complete substitution

Rather than describe the calculation, here it is end to end — every substitution in order, starting from the inputs above. Starting figures: Shutter speed without filter (seconds — 1/250 = 0.004), Filter specified as, Strength in stops, Optical density (D). Run to the end, the new shutter speed resolves to 4.1 s — 10.0 stops darker · exposure multiplied by 1,024× on the bands this tool uses.

Strength is given directly: 10.00 stops (factor 2^10.00 = 1,024.0×).
Exposure factor = 2^10.00 = 1,024.0× — the filter passes only 1/1,024 of the light.
New shutter speed = 0.0040 s × 1,024.0 = 4.10 s.
Formatted for the camera dial: 4.1 s.

Exposure factor — 1,024.0 ×. This is the number experienced users quote when the headline alone would mislead.

Strength in stops — 10.0 stops. Compare it against the main result of 4.1 s before drawing conclusions.

Optical density — 3.01 D. Compare it against the main result of 4.1 s before drawing conclusions.

Marketing name — ND1,024. If your inputs change, this is usually the first companion figure to move.

New shutter speed (seconds) — 4.10 s. This is the number experienced users quote when the headline alone would mislead.

Re-running with your own figures is instant; re-running by hand once is the best way to know the tool is telling you the truth.

Interpreting the Shutter Speed verdict

The value above only becomes useful the moment you know what it is being measured against. The default case lands in the “10.0 stops darker · exposure multiplied by 1,024×” band, and bands are deliberately wide because real situations overlap. The practical reading rules: compare against your own history before comparing against other people; treat band boundaries as zones, not walls — one point on the wrong side of a threshold rarely changes a real outcome; and when a companion output contradicts the headline, believe the pair.

In Arts, Music & Creative, Shutter Speed is one instrument in an orchestra: on its own it is a number, next to Exposure factor and Strength in stops it becomes a diagnosis. The tools linked above exist so the headline never has to carry that weight alone.

The errors that quietly break a Shutter Speed figure

Meter and focus before fitting a strong ND — through an 10-stop filter the viewfinder is black and autofocus hunts. Switch to manual focus, compose, lock it, then fit the filter (or use live-view magnification). Expect a small exposure bias: many filters, especially variable NDs (two stacked polarisers), lose a fraction of a stop beyond their rating and add a warm or magenta cast. Cheap variable NDs also show a "X" pattern of uneven extinction at their darkest settings. For exposures past 30 seconds use bulb mode with a remote release, and cover the viewfinder eyepiece — light leaking through it registers on long exposures. Finally, at 10+ stops, verify with the histogram rather than the LCD preview.

Confusing a large number with an important one. Shutter Speed can be dominated by one input whose absolute value looks unimpressive, which is why this page ranks influence separately from magnitude.

A final trap is presentation: reporting Shutter Speed to more decimal places than the inputs support. The tool prints what the arithmetic gives; you should quote only what your least precise field justifies.

A quick check for any Shutter Speed figure

Record the date and the inputs alongside the number so future-you knows what was assumed.
Compare the result with one independent method or published benchmark.
Confirm the inputs are dated — a Shutter Speed figure should carry the date it was computed.
Confirm the example values are plausible for your own situation before replacing them.
Re-run the calculation with a ±10 % stress on the two most sensitive inputs.
Run the ±10 % stress on the top two levers and check that your conclusion survives both.

Step by step: getting a trustworthy Shutter Speed out of this tool

The tool does the arithmetic; the routine below is what makes the arithmetic trustworthy. Five steps, a minute total — and afterwards you will know not just what the number is, but which assumption produced it.

Step 1 — collect, then type. Everything this tool asks for is listed above (shutter speed without filter (seconds — 1/250 = 0.004), filter specified as, strength in stops, optical density (d), filter factor (×)). Pull each figure from something you can point at — paperwork, a dashboard, a label — before touching a field. Guesswork at the input stage cannot be repaired at the interpretation stage. Write the figure down before moving on; memory flatters whichever number you saw last.

Step 2 — compute the version you would not be embarrassed by. If a stranger audited your inputs, which set would you hand over? Enter that set, read the result, and treat everything else as upside. Numbers are cheap to produce and expensive to retract; the extra minute is the cheapest insurance available.

Step 3 — change one input at a time. Nudge a single field by ten percent, watch the headline and its companions move, then undo it. Two or three fields will dominate — the sensitivity table above already ranks them for this engine. Comparisons are cheap: run the identical calculation for the alternative and look at the gap.

Step 4 — compute a corridor, not a point. Three runs — worst, likely, best — turn Shutter Speed from a snapshot into a range. Plan against the pessimistic end and treat the optimistic end as the upside story. If the verdict changes with a ten-percent nudge, report the nudge alongside the number.

Step 5 — schedule the next run. In Arts, Music & Creative the inputs drift quietly. Put a reminder a quarter out, re-enter the same fields, and read the change rather than the level. The test of a good estimate is not that it feels right but that it changes what you do.

Where Shutter Speed matters in practice

Arts, Music & Creative arguments end at arithmetic or they do not end. Shutter Speed is the arithmetic: 4.1 s on the example inputs, reproducible by anyone who types the same numbers. Rounding early is the quietest way to introduce a permanent error.

Used properly this is a five-minute filter that saves weeks. Compute Shutter Speed, reject what fails, and only then bring in the expensive analysis for the survivors. A result worth acting on survives having its two shakiest inputs halved.

There is a personal-administration use people overlook: periodic self-checking. Shutter Speed quietly drifts as life changes — rates move, bodies change, costs compound — and re-running it a few times a year catches drift while correction is still cheap. A calculation you cannot explain to somebody else is a calculation you cannot defend.

Key terms on this page

Exposure factor: 1,024.0 × in the default Shutter Speed calculation — one of the secondary figures an experienced reader checks before trusting the primary number.
Strength in stops: 10.0 stops on the example inputs — a companion figure printed beside the headline of Shutter Speed so that no result is read in isolation.
Optical density: 3.01 D in the default Shutter Speed calculation — one of the secondary figures an experienced reader checks before trusting the primary number.
New shutter speed: The primary output of this tool: 4.1 s for the default inputs, computed exactly from t_new = t_old × 10^(D/10) for optical density D; t_new = t_old × 2^stops; stops = D × 3.3219 = log₂(filter factor).
Worked example: Every substitution in order, from the example inputs to 4.1 s — the audit trail for the headline figure.
Verdict band: The plain-language label — here “10.0 stops darker · exposure multiplied by 1,024×” — mapping the computed figure onto experience-based ranges for Arts, Music & Creative.

Methodology, sources and limits

There is no black box on this page — the engine evaluates t_new = t_old × 10^(D/10) for optical density D; t_new = t_old × 2^stops; stops = D × 3.3219 = log₂(filter factor). Source of record: CIPA DC-004 filter conventions; ISO 9358 optical density definitions (D = −log₁₀ transmittance); manufacturer data sheets (B+W, Lee, Hoya, NiSi) for filter-factor equivalences. Where a professional version of this calculation differs, it differs in inputs and jurisdiction-specific coefficients, not in the algebra — which is why re-checking your inputs beats hunting for a second calculator.

Nothing here replaces a qualified professional, and nothing here is approximate either — the arithmetic is exact, and the honesty is in the inputs you supply. Every intermediate value is printed so that the result can be checked line by line rather than accepted or rejected wholesale.

Turning this Shutter Speed into a decision

Re-run the calculation with your own figures, stress the two most sensitive inputs by ±10 %, and only then act on the result.

Whoever you are (people who need one trustworthy number before their next decision), the next step is the same: replace the example inputs with your own, note the date, and re-run whenever a figure moves. In Arts, Music & Creative, a dated figure is a trend, and an undated one is a rumour.