ND Filter Calculator
This ND filter calculator shows how long you have to expose with a neutral density filter: enter the time without filter and the filter strength, then read the new exposure time, stops and density.
Source: Wikipedia – Neutral-density filter (Filterfaktor, Dichte, Blendenstufen). Updated: .
How it is calculated
At 1/125 second with an ND1000 filter (10 stops) the exposure time comes to about 8 seconds. The calculator multiplies the time without filter by the filter factor and shows time, stops and density.
How it is calculated
Each stop doubles the required exposure time. A filter of n stops therefore has the factor 2 to the power of n: ND8 is 3 stops and factor 8, ND64 is 6 stops. The optical density (OD) is stops times 0.301; ND8 equals OD 0.9 and ND1000 about OD 3.0. The new time is time times factor. Several filters in a row add their stops: ND8 and ND64 make 9 stops, so ND512.
Tips for long exposures
- Set framing, focus and aperture before you attach the filter, because with dense filters you can hardly see anything.
- On SLR cameras cover the viewfinder so that no stray light comes in from behind.
- From about 30 seconds many cameras need bulb mode. A tripod and a remote release help.
More photo tools: the depth of field calculator, the crop factor calculator and the time-lapse calculator.
Frequently asked questions
How do I calculate exposure time with an ND filter?
Multiply the time without filter by the filter factor. With ND1000 (factor 1024) 1/125 s becomes about 8 s.
How many stops is an ND1000?
Ten stops, because 2 to the power of 10 is 1024. The density is 3.0.
What do ND8, ND64 or ND1000 mean?
The number is the factor by which the filter weakens light: ND8 absorbs three stops, ND64 six, ND1000 ten.
Can I stack two ND filters?
Yes, the stops add up. Color casts and vignetting may increase though, especially with wide-angle lenses.
Sources and legal basis
- Wikipedia – Neutral-density filter (Filterfaktor, Dichte, Blendenstufen)
- Wikipedia – Reciprocity (photography) (reciprocity failure in long exposures)
As of: · Editorial policy
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