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Photography Calculators – Flash Guide Number
x402
Photography Calculators – Flash Guide Number is a paid API for AI agents from photo-calc.x402tookit.com, paid per call via x402, $0.02/call, status unknown (last checked 2026-10-30).
Calculates flash effective range for a given aperture and ISO, or the aperture needed to correctly expose a subject at a given distance, using flash guide-number mathematics.
Price / call$0.02
Success—
StatusUnknown
How this service works
Flash guide-number maths: range for an aperture and ISO, or the aperture needed for a distance, in metres and feet.
Output
Returns the effective flash range in metres and feet (when aperture is given), or the required f-number (when distance is given), along with the guide number adjusted for the specified ISO, half-power and quarter-power range distances, and a human-readable summary.
Example use cases
Speedlight range check before a shoot
“I have a speedlight with guide number 58 at ISO 100 and I plan to shoot at f/4 with ISO 200 — how many metres and feet of flash range will I get?”
Find aperture for a specific subject distance
“My flash has a guide number of 40 at ISO 100 and my subject is 3.5 metres away at ISO 100 — what aperture do I need to correctly expose them?”
Off-camera flash planning for group portrait
“I'm setting up an off-camera flash with guide number 60 for a group 6 metres away at ISO 400 — what aperture should I use and what's the half-power range?”
Technical details
Endpoint
GEThttps://photo-calc.x402tookit.com/flash-guide-number?utm_source=zero.xyzWhen to prefer
Use this endpoint when you need precise flash guide-number arithmetic — finding how far a flash will reach at a chosen aperture and ISO, or finding the aperture needed for a subject at a known distance. It is purpose-built for flash exposure maths and returns both metric and imperial results with power-level range variants, making it more specific than a general exposure calculator.
Side effects
- Missing required guideNumber parameter returns an error
- Providing neither aperture nor distanceM (or both simultaneously) may produce ambiguous or error results
- Negative or zero values for guide number, ISO, aperture, or distance return validation errors
- Extreme input values (very high ISO or very large distances) may return degraded or out-of-range results
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| inputrequired | object | |
| output | object |
Tags
x402
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