How do ND filter stops translate to shutter speed changes?

Starting from a 1/125s base exposure, a 3-stop ND filter lengthens the shutter speed needed to roughly 1/16s, a 6-stop ND to about half a second, and a 10-stop ND (commonly labeled ND1000) to roughly 8.2 seconds — each additional stop of density doubles the shutter speed required to hold the same total exposure.

Why This Chart Uses One Specific Starting Point

Every row here scales from a 1/125s base exposure, which is a realistic bright-daylight shutter speed at a moderate aperture and ISO, but it's just a starting point — the actual shutter speed you need is your correctly metered exposure without the filter, multiplied by two for every stop of ND density. A darker starting scene needs a slower base shutter speed before the filter is even applied, which shifts every row in this table proportionally longer.

Why Manufacturers Label Filters by Density Factor, Not Stops

ND2, ND8, ND1000 and similar labels describe how many times darker the filter makes the scene (2x, 8x, 1000x), not the stop count directly — converting requires taking log base 2 of the density factor, which is why ND1000 works out to 10 stops (2^10 = 1024, close enough to 1000 that manufacturers round to the cleaner number) rather than an obviously round stop count.

Work out the exact shutter speed for your own base exposure and filter in the Exposure Triangle Solver.