ND Filter Calculator
Find the right shutter speed for long exposure and neutral density photography. Enter base exposure and filter strength (stops or ND density), stack multiple filters, and use red light mode in the field.
What this calculator does
This ND filter calculator gives you the final shutter speed after adding one or more neutral density filters. Enter your base shutter speed (presets from 1/64000 to 30 s or a custom value in seconds), then add filters by stop strengthโfrom 1 stop (ND2) up to 20 stops (ND1M). You can stack multiple filters; stops add (e.g. 6-stop + 3-stop = 9 stops). The result is shown as a fraction for short times (e.g. 1/10 s) or as hours:minutes:seconds for long exposures. The tool rounds to the nearest 1/3-stop camera setting when useful. Red light mode and fullscreen are there for use in the field.
Stops vs. density
Filter strength is either in stops (each stop halves the light, so exposure time doubles) or optical density (ND 0.3 โ 1 stop, ND 1.8 = 6 stops = ND64). The math is with n = total stops. The calculator uses stops; the table in the info hub above maps common ND factors (ND2, ND4, โฆ ND1000) to stop values so you can match your filter to the tool.
Reciprocity and viewfinder
On film, very long exposures often need more time than the ND formula suggests (reciprocity failure); digital sensors donโt have this, so the result is accurate for digital. For DSLRs, cover the viewfinder during long exposures so stray light doesnโt affect the image; mirrorless cameras donโt have this issue.
ND Filter Calculator FAQ
? How do I use the ND filter calculator?
Pick your base shutter speed (e.g. 1/100s from the dropdown or enter a custom value in seconds). Add one or more filters and set each filterโs strength in stops (presets like 6 stops / ND64 are available). The tool shows the final shutter speed as a fraction for short times or as H:M:S for long exposures. Use red light mode and fullscreen when youโre out in the field.
? Can I stack multiple ND filters?
Yes. Hit โAdd filterโ for each filter and choose its strength. Stops add: for example 6 stops plus 3 stops gives 9 stops total. The calculator multiplies your base exposure by 2 raised to the total number of stops to get the final shutter speed.
? What is reciprocity failure?
On film, very long exposures often need more time than the simple ND math suggestsโthe emulsion becomes less sensitive over time. Digital sensors donโt have reciprocity failure, so the calculatorโs result is accurate for digital. For film, add extra time according to your filmโs data sheet.
? Why cover the viewfinder on a DSLR for long exposures?
Light can leak through the viewfinder and reach the sensor, which can cause flare or ruin the shot. Use the built-in viewfinder curtain or a dedicated cover. Mirrorless cameras donโt have this problem.