ND filter calculator
ND filter & long exposure calculator
Every stop of ND doubles your shutter time. Pick the shutter speed you metered and the filter you own to get the real exposure time; stacking and extra compensation are included.
Exposure time—
Light reduction—
Light factor—
Aperture equivalent—
To keep the metered shutter instead, open the aperture by the same number of stops.
Anything past about 10 minutes should be test-shot; reciprocity failure may also apply at very long times.
Common conversions
| Metered | ND4 (+2) | ND8 (+3) | ND64 (+6) | ND1000 (+10) |
|---|---|---|---|---|
| 1/250 | 1/63s | 1/31s | 0.256s | 4.1s |
| 1/125 | 1/31s | 0.064s | 0.512s | 8.2s |
| 1/60 | 1/15s | 0.133s | 1.1s | 17s |
| 1/30 | 0.133s | 0.267s | 2.1s | 34s |
| 1/15 | 0.267s | 0.533s | 4.3s | 1m 8s |
| 1/8 | 1/2s | 1s | 8s | 2m 8s |
| 1/4 | 1s | 2s | 16s | 4m 16s |
| 1/2 | 2s | 4s | 32s | 8m 32s |
| 1s | 4s | 8s | 1m 4s | 17m 4s |
Pure light arithmetic. Does not include reciprocity failure, filter colour cast or metering error, and mechanical shutters can drift at the slowest settings.