HDR Bracketing Calculator

Features

• Real coverage = `(frames - 1) x interval + single-frame dynamic range`
• Solves the minimum frame count and gives a separate verdict on whether it is enough
• A symmetric exposure sequence: three frames are -D/0/+D, four are -1.5D/-0.5D/+0.5D/+1.5D
• Give the scene range directly in EV, or as the brightest minus the darkest spot
• Enter a manual frame count to check whether it suffices
• With noise in mind, take one more frame for shadow stacking
• The verdict is colour-coded: covered, just enough, or not enough
• Everything runs locally and nothing is uploaded

How to use

1. Pick how to give the scene range and enter the scene and camera ranges
2. Enter the bracket interval (2 EV covers most scenes)
3. Enter a manual frame count to test it (0 uses the automatic value)
4. Read the verdict: whether it covers the scene and by how much

FAQ

How is the frame count worked out?

Each frame covers the single-frame dynamic range and neighbours are offset by one interval, so N frames at interval D cover (N-1)*D + the single-frame range. The tool solves that inequality for the minimum count and reports both the actual coverage and the headroom. Knowing the frame count alone is not enough.

Why must the exposure sequence be symmetric?

Three frames are -D/0/+D and four are -1.5D/-0.5D/+0.5D/+1.5D, from the general form (i - (N-1)/2)*D. Writing -2/-1/0/+1 instead puts the centre of gravity on the bright side, so the merged midtones shift while the picture still looks plausible, which makes it hard to spot afterwards.

What interval should I use?

Two EV covers most scenes with fewer frames and simpler merging. For a very wide range or smoother transitions, use 1 EV or even 2/3 EV, at the cost of more frames. An interval of zero or less is meaningless (zero makes the frame count infinite), and the tool rejects it.

Why take one more frame for noise?

Shadow noise is reduced by stacking several exposures, so one more frame is worth taking. The cost is a longer total capture time, which makes hand-held shooting harder; a tripod is a better thing to fix first.