What is exposure bracketing?

It is shooting the same scene at several exposures, some darker and some brighter than the meter reading, so you capture detail across the full brightness range. The frames are later merged for HDR or used to pick the best single exposure.

How does the calculator convert stops to values?

Each stop doubles or halves the light. For shutter and ISO the value is multiplied by two to the power of the EV offset. For aperture the f-number is multiplied by the square root of two to the power of the offset, because aperture controls light by area.

Which parameter should I bracket?

For HDR landscapes vary the shutter speed so depth of field and noise stay constant. Avoid bracketing aperture because it changes depth of field between frames, and avoid bracketing ISO because it changes noise. Shutter bracketing is almost always the right choice for static scenes.

How many frames do I need for HDR?

Three frames at plus and minus 2 stops covers most scenes. High-contrast scenes such as a bright window in a dark room benefit from five or seven frames spanning plus and minus 3 stops. More frames give smoother tonal transitions but require a steady tripod.

What step size is best?

Full-stop steps give the widest coverage with the fewest frames and are ideal for handheld HDR. Half or third-stop steps give finer overlap for very high dynamic range or when blending shadows precisely, at the cost of more frames and more storage.

What is the Exposure Bracketing Calculator?

Build a set of bracketed exposures at plus and minus 1, 2 or 3 stops in full, half or third-stop steps around a base exposure. Outputs the exact shutter speed, aperture or ISO value for each frame, ready for HDR and focus-stacking workflows. It runs free in your browser on Gera Tools, with nothing uploaded.

Exposure Bracketing Calculator

Name: Exposure Bracketing Calculator
Creator: Gera Tools
License: https://creativecommons.org/licenses/by/4.0/

Bracketing is how you beat a scene whose brightness range exceeds what one exposure can hold. This calculator builds the full bracket for you — pick a base exposure, a span and a step, and it prints every frame’s exact shutter speed, aperture or ISO value from darkest to brightest.

How it works

Each stop is a doubling or halving of light, so converting an EV offset to a real camera value depends on which parameter you vary.

Shutter speed and ISO are linear in light:

value = base × 2^(EV offset)

A base of 1/125 s bracketed +2 EV becomes (1/125) × 2^2 = 1/31 s ≈ 1/30 s.

Aperture controls light by area, so the f-number scales by the square root of two per stop:

f-number = base × (√2)^(EV offset)

A base of f/8 bracketed +1 EV (one stop darker, smaller opening) becomes 8 × √2 ≈ f/11. The tool handles the sign correctly: a positive EV offset always means a brighter frame, so for aperture it moves to a smaller f-number.

Building the sequence

You choose:

Span — plus and minus 1, 2 or 3 stops around the base.
Step — full (1 EV), half (0.5 EV) or third (0.333 EV) increments.

The number of frames is (2 × span ÷ step) + 1, always an odd number with the base exposure in the centre.

Worked example: a sunset landscape

You meter the mid-tones at 1/60 s, f/11, ISO 100, but the bright sky and dark foreground clearly exceed one exposure. You choose a ±2 stop bracket in full-stop steps. The sequence the calculator produces:

Frame	EV offset	Shutter speed	Purpose
1	−2 EV	1/250 s	Expose the bright sky
2	−1 EV	1/125 s	Slight underexposure
3	0 EV	1/60 s	Metered base frame
4	+1 EV	1/30 s	Slight overexposure
5	+2 EV	1/15 s	Expose the dark shadow

Aperture stays f/11 and ISO stays 100 throughout, so noise and depth of field are identical in every frame. The five images merge cleanly in Lightroom, Photomatix, or any HDR-capable editor.

Choosing span and step for your scene

A ±1 stop bracket (three frames) handles moderate contrast situations — a person backlit by a bright window, for example. The tonal range is 2 stops, which most cameras record across a 3-frame AEB set.

A ±2 stop bracket covers roughly 4 stops of extra range and is the most common choice for architectural interiors and real estate photography, where the view through a window is always much brighter than the room.

A ±3 stop bracket in third-stop steps produces 19 frames and maps the full dynamic range of extreme scenes such as a church interior with stained glass. Tone-mapping from this many frames gives very smooth gradations but requires a sturdy tripod and a scene with no moving elements.

Half-stop and third-stop steps add more overlap between frames, which is helpful for high-bit-depth blending workflows. For straight HDR tone-mapping, full-stop steps are usually enough.

Notes and tips

Bracket the shutter for static scenes. It keeps depth of field and noise constant across the set — essential for clean HDR merges.
Use a tripod for anything beyond three frames so the frames align.
Watch the slow end. Bracketing +3 EV from a handheld 1/60 s pushes you to 1/8 s, well into shake territory — the tool flags very slow resulting shutter speeds.
Enable auto-exposure bracketing (AEB) on your camera to fire the sequence automatically in one press, reducing alignment errors.

All calculations run locally in your browser.