{"uid":"cap_dGGIGKcFr99fvdMIVWI3N","slug":"photography-calculators-shutter-speed-rules-1197905b","name":"Photography Calculators – Shutter Speed Rules","description":"Minimum handheld shutter speed (reciprocal rule) and the longest star-point exposure by the 500 rule and the NPF rule.","url":"https://photo-calc.x402tookit.com/shutter-rule?utm_source=zero.xyz","method":"GET","headers":{},"bodySchema":{"type":"object","$schema":"https://json-schema.org/draft/2020-12/schema","required":["input"],"properties":{"input":{"type":"object","required":["type","method"],"properties":{"type":{"type":"string","const":"http"},"method":{"enum":["GET"],"type":"string"},"queryParams":{"type":"object","required":["focalMm"],"properties":{"sensor":{"type":"string","description":"full-frame (default), aps-c, micro-four-thirds etc."},"focalMm":{"type":"number","description":"Actual focal length in mm"},"aperture":{"type":"number","description":"f-number (for the NPF star rule)"},"pixelPitchUm":{"type":"number","description":"Sensor pixel pitch in micrometres (for the NPF rule)"},"declinationDeg":{"type":"number","description":"Declination of the stars, 0 at the celestial equator (default 0)"},"stabilisationStops":{"type":"number","description":"Lens or body image stabilisation in stops (default 0)"}}}},"additionalProperties":false},"output":{"type":"object","required":["type"],"properties":{"type":{"type":"string"},"example":{"type":"object","properties":{"asOf":{"type":["null","string"]},"npfS":{"type":["null","number"]},"sensor":{"type":["null","string"]},"source":{"type":["null","string"]},"focalMm":{"type":["null","number"]},"reasons":{"type":["array","null"],"items":{"type":"string"}},"summary":{"type":["null","string"]},"verdict":{"type":["null","string"]},"degraded":{"type":["boolean","null"]},"cropFactor":{"type":["null","number"]},"disclaimer":{"type":["null","string"]},"notChecked":{"type":["array","null"],"items":{"type":"string"}},"starRule400S":{"type":["null","number"]},"starRule500S":{"type":["null","number"]},"equivalentFocalMm":{"type":["null","number"]},"npfAtDeclinationS":{"type":["null","number"]},"handheldMinShutter":{"type":["null","string"]},"handheldMinShutterS":{"type":["null","number"]},"starRule500FullFrameS":{"type":["null","number"]},"handheldWithStabilisation":{"type":["null","string"]},"handheldWithStabilisationS":{"type":["null","number"]}}}}}}},"responseSchema":null,"example":null,"exampleRequest":null,"tags":["x402"],"displayCostAmount":"0.02","displayCostAsset":"USDC","priceDynamic":false,"priceHint":null,"priceStatus":"priced","priceSource":"probe","requiresHandshake":false,"reviewCount":0,"rating":{"score":"0.00","successRate":"0.00","reviews":0,"stars":null,"state":"unrated"},"availabilityStatus":"unknown","priceObserved":null,"sessionDeposit":null,"pricing":{"kind":"static","summary":"$0.02/call","primary":{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.02","per":"call","confidence":"exact"},"accepted":[{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.02","per":"call","confidence":"exact"}]},"paymentMethods":[{"uid":"pm_ZSttwsSx7pmFiwKGwzydx","protocol":"x402","methodType":"crypto","chain":"base","mode":"charge","costAmount":"0.02","costPer":"request","priority":0,"asset":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","unit":"request","depositMicros":null,"planRef":null}],"brandName":null,"brandSlug":null,"brandBaseUrl":null,"brandDocsUrl":null,"whatItDoes":"Returns minimum handheld shutter speed (reciprocal rule) and maximum star-trail-free exposure times (500 rule and NPF rule) for a given focal length, sensor, and optional parameters.","exampleAgentPrompt":"Using a 24mm lens at f/2.8 on a full-frame sensor with a pixel pitch of 4.4µm, what's the minimum safe handheld shutter speed and the longest star-point exposure by the NPF rule at the celestial equator?","exampleUseCases":[{"title":"Astrophotography star-point exposure planning","prompt":"I'm shooting the Milky Way tonight with a 14mm f/2.8 lens on a full-frame camera — pixel pitch is 5.9µm, and the stars I want are near the celestial equator. What's the longest exposure I can use with the NPF rule before stars start to trail?"},{"title":"Handheld telephoto minimum shutter check","prompt":"I'm shooting sports with a 200mm lens on an APS-C camera that has 2 stops of image stabilisation. What's the minimum handheld shutter speed I should use, with and without accounting for the stabilisation?"},{"title":"Star exposure comparison across rule systems","prompt":"For a 24mm lens on a micro-four-thirds sensor at f/1.8, can you give me the star-trail-free exposure times from both the 500 rule and the NPF rule so I can compare them?"}],"resultDescription":"A JSON object containing: minimum handheld shutter speed (as a fraction string and seconds), handheld speed with stabilisation, star exposure limits from the 400, 500, and NPF rules (in seconds), equivalent full-frame focal length, crop factor, sensor name, summary verdict text, and any warnings or disclaimers.","failureModes":["Missing required focalMm parameter returns a validation error","Very extreme focal lengths (e.g. <1mm or >10000mm) may produce unreliable results","NPF rule outputs may be null if aperture or pixelPitchUm are not provided","Invalid sensor string defaults to full-frame without warning","Negative or zero stabilisationStops may produce unexpected handheld values"],"whenToPreferThis":"Choose this endpoint when you need quick, standards-based shutter speed recommendations for handheld shooting or astrophotography star-point exposures across multiple rules (reciprocal, 500, NPF) in a single call. It is especially valuable when shooting conditions require comparing NPF precision against the simpler 500-rule, or when IS/IBIS stops need factoring in. Use alternatives if you need full manual EV calculation or exposure bracketing.","instructions":null,"reviewSummary":null,"reviewSummaryHighlights":null,"reviewSummaryConcerns":null,"reviewSummaryGeneratedAt":null,"activationCount":0,"lastUsedAt":null,"lastSuccessfullyRanAt":null,"lastHealthCheckAt":"2026-10-29T13:13:40.462Z","isFirstParty":false,"canonicalSlug":"photography-calculators-shutter-speed-rules-1197905b"}