HDR Bracket Calculator

This calculator figures out how many bracketed exposures you need to capture a high-contrast scene without losing detail in the highlights or shadows, and what shutter speeds each bracket should use. It starts from the scene's total dynamic range — the EV difference between your brightest and darkest metered points — and subtracts however much of that your camera's sensor can already handle in one shot (its native dynamic range, typically 11-15 stops). Whatever range is left over gets divided by your chosen EV spacing between brackets to determine how many additional exposures are needed, plus one for the base exposure; the calculator then rounds this up to the next odd number, since cameras' auto-bracket features are built around a symmetrical sequence centered on a metered middle exposure.

From the middle EV (the average of your brightest and darkest readings) it derives the middle shutter speed at your chosen aperture and ISO using the standard EV formula, then works outward in stops to get the fastest (brightest-bracket) and slowest (darkest-bracket) shutter speeds, plus the combined shooting time for the whole sequence. A key assumption is that aperture and ISO stay fixed across all brackets — only shutter speed varies, which is standard practice for HDR since it avoids depth-of-field or noise shifts between frames. Also note the EV readings you enter should come from spot-metering the actual highlight and shadow areas of your scene, not a single average reading, or the bracket count will underestimate what the scene really needs.