{"success":true,"version":"v1","request":{"tool":"get_calculator_schema","calculator_id":"nd-filter-exposure"},"result":{"entity_type":"calculator","id":"nd-filter-exposure","calculator_id":"nd-filter-exposure","canonical_url":"https://tttkmbb.com/photography/nd-filter-exposure","name":"ND Filter Exposure Calculator","title":"ND Filter Exposure Calculator – Long-Exposure Shutter Speed for a Neutral-Density Filter","category":"photography","category_name":"Photography & Optics","tool_name":"calculate_nd_filter_exposure","featured_mcp_tool":false,"description":"Computes the shutter speed needed after adding a neutral-density filter given in stops or as a filter factor (ND8, ND64, ND1000 ...), plus the filter's optical density and a table of resulting shutter speeds for common filters.","use_when":"You know the correctly exposed shutter speed without a filter and want the exposure time with an ND filter, or need to convert between ND stops, filter factor and optical density.","do_not_use_when":"The change comes from aperture or ISO rather than a filter (use equivalent-exposure), or you need the exposure value itself (use exposure-value).","inputs":[{"name":"base_shutter_seconds","label":"Shutter speed without filter","type":"number","unit":"s","required":true,"max":86400,"exclusive_min":0,"description":"Exposure time in seconds. Enter fractions as decimals: 1/125 s = 0.008, 1/60 s = 0.016667, 1/1000 s = 0.001.","example":0.016667},{"name":"nd_stops","label":"ND filter strength","type":"number","unit":"stops","required":false,"min":0,"max":30,"description":"Filter strength in stops (3-stop, 6-stop, 10-stop ...). Give this or nd_factor; when both are given nd_stops is used.","example":10},{"name":"nd_factor","label":"ND filter factor","type":"number","required":false,"min":1,"max":1000000000,"description":"Filter factor as in the ND name: ND8 = 8, ND64 = 64, ND1000 = 1000 (stops = log2(factor)).","example":1024}],"outputs":[{"name":"new_shutter_seconds","label":"Shutter speed with filter","type":"number","unit":"s","decimals":4,"description":"base_shutter_seconds × 2^stops."},{"name":"new_shutter_text","label":"Shutter speed with filter (text)","type":"string","decimals":4,"description":"The same value as a fraction or seconds, e.g. '1/15 s' or '17.07 s'."},{"name":"stops","label":"Stops","type":"number","unit":"stops","decimals":2,"description":"Light reduction in stops (log2 of the filter factor)."},{"name":"nd_factor","label":"Filter factor","type":"number","decimals":2,"description":"2^stops: how many times less light reaches the sensor."},{"name":"optical_density","label":"Optical density","type":"number","decimals":2,"description":"log10(filter factor): the ND value printed on some filters (0.9 = 3 stops, 3.0 = 10 stops)."},{"name":"filter_table","label":"Shutter speed by common filter","type":"object","unit":"s","decimals":4,"description":"Resulting shutter speed in seconds for ND2, ND4, ND8, ND16, ND64, ND400 and ND1000 from the same base speed."}],"input_schema":{"type":"object","properties":{"base_shutter_seconds":{"description":"Exposure time in seconds. Enter fractions as decimals: 1/125 s = 0.008, 1/60 s = 0.016667, 1/1000 s = 0.001. Unit: s.","type":"number","maximum":86400,"exclusiveMinimum":0,"examples":[0.016667],"x-unit":"s"},"nd_stops":{"description":"Filter strength in stops (3-stop, 6-stop, 10-stop ...). Give this or nd_factor; when both are given nd_stops is used. Unit: stops.","type":"number","minimum":0,"maximum":30,"examples":[10],"x-unit":"stops"},"nd_factor":{"description":"Filter factor as in the ND name: ND8 = 8, ND64 = 64, ND1000 = 1000 (stops = log2(factor)).","type":"number","minimum":1,"maximum":1000000000,"examples":[1024]}},"additionalProperties":false,"required":["base_shutter_seconds"]},"output_schema":{"type":"object","properties":{"new_shutter_seconds":{"description":"base_shutter_seconds × 2^stops. Unit: s.","type":"number","x-unit":"s"},"new_shutter_text":{"description":"The same value as a fraction or seconds, e.g. '1/15 s' or '17.07 s'.","type":"string"},"stops":{"description":"Light reduction in stops (log2 of the filter factor). Unit: stops.","type":"number","x-unit":"stops"},"nd_factor":{"description":"2^stops: how many times less light reaches the sensor.","type":"number"},"optical_density":{"description":"log10(filter factor): the ND value printed on some filters (0.9 = 3 stops, 3.0 = 10 stops).","type":"number"},"filter_table":{"description":"Resulting shutter speed in seconds for ND2, ND4, ND8, ND16, ND64, ND400 and ND1000 from the same base speed. Unit: s.","type":"object","x-unit":"s"}}},"formula":"stops = nd_stops or log2(nd_factor); new_shutter_seconds = base_shutter_seconds × 2^stops; optical_density = log10(2^stops)","method":"Assumes the filter is neutral and the scene light is constant; a marketed 'ND1000' is 9.97 stops (2^10 = 1024). Exposures beyond about 30 s need bulb mode, and film needs reciprocity-failure compensation.","sources":[{"name":"Wikipedia – Neutral-density filter","url":"https://en.wikipedia.org/wiki/Neutral-density_filter","type":"reference","retrieved_at":"2026-09-24"},{"name":"Wikipedia – Exposure value","url":"https://en.wikipedia.org/wiki/Exposure_value","type":"reference","retrieved_at":"2026-09-24"}],"freshness":{"type":"static","max_age_seconds":null,"note":"Deterministic formula with fixed constants; results never go stale. Inputs supplied by the caller determine the output."},"examples":[{"name":"1/60 s with a 10-stop filter","inputs":{"base_shutter_seconds":0.016667,"nd_stops":10},"expected":{"new_shutter_seconds":17.067,"stops":10,"nd_factor":1024,"optical_density":3.01},"url":"https://tttkmbb.com/api/v1/calculate/nd-filter-exposure?base_shutter_seconds=0.016667&nd_stops=10"},{"name":"1/125 s with an ND8 filter","inputs":{"base_shutter_seconds":0.008,"nd_factor":8},"expected":{"new_shutter_seconds":0.064,"stops":3,"optical_density":0.9,"new_shutter_text":"1/16 s"},"url":"https://tttkmbb.com/api/v1/calculate/nd-filter-exposure?base_shutter_seconds=0.008&nd_factor=8"}],"faq":[{"q":"Is ND1000 the same as a 10-stop filter?","a":"Almost: ND1000 reduces light 1000× = 9.97 stops, a true 10-stop filter 1024×; the 0.03-stop difference is far below camera exposure tolerance."},{"q":"How do I read the optical-density marking?","a":"Density d means a factor of 10^d: ND 0.3 = 1 stop, 0.9 = 3 stops, 1.8 = 6 stops, 3.0 = 10 stops (each 0.3 of density is one stop)."}],"tags":["nd filter","neutral density","long exposure","10 stop filter","filter factor","optical density"],"related":[{"calculator_id":"equivalent-exposure","reason":"Compensate with aperture or ISO instead of shutter speed."},{"calculator_id":"exposure-value","reason":"Exposure value of the base setting."}],"links":{"html":"https://tttkmbb.com/photography/nd-filter-exposure","markdown":"https://tttkmbb.com/photography/nd-filter-exposure.md","json":"https://tttkmbb.com/photography/nd-filter-exposure.json","api":"https://tttkmbb.com/api/v1/calculate/nd-filter-exposure","schema":"https://tttkmbb.com/api/v1/calculators/nd-filter-exposure","openapi":"https://tttkmbb.com/openapi.json","mcp":"https://tttkmbb.com/mcp"},"version":"v1","updated_at":"2026-09-24"},"timestamp":"2026-09-24T03:47:35Z"}