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Flash Guide Number Aperture Estimate

Online flash guide number aperture estimate. Guide number must be quoted at ISO 100 for the chosen zoom and modifier.

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flash guide number aperture calculator online

Use flash guide number aperture estimate online for guide number m, distance m, ISO. Guide number must be quoted at ISO 100 for the chosen zoom and modifier. Geometric or data-budget estimate. Sensor behavior, processing, focus breathing and recording overhead are excluded unless explicitly modeled.

How to use it

Enter guide number m. Set distance m, ISO. Select Calculate and check the labeled output. Copy or download the JSON result.

Options and example settings

OptionChoices / valueExample default
guide number mMain input. Positive values. 40
distance mOption. Positive values. 5
ISOOption. Positive values. 100

Calculation method

f_number = guide_number_m*sqrt(ISO/100)/distance_m (^ means exponentiation; trig functions ending in d use degrees).

Worked examples

Apply flash guide number aperture estimate to the case below, keeping the displayed units and assumptions. Guide number must be quoted at ISO 100 for the chosen zoom and modifier.

Flash Guide Number Aperture Estimate — worked case

Settings: distance m: 5; ISO: 100

Input:

40

Calculated result for these inputs:

Output:

{
  "f_number": 8
}

Choose the right tool

Exposure equivalence, depth-of-field equivalence and file storage describe different questions. Review whether a value is a focal length, a crop factor, a shutter time, a frame rate or a bitrate before calculating.

Limitations and common mistakes

  • Guide number must be quoted at ISO 100 for the chosen zoom and modifier. Geometric or data-budget estimate. Sensor behavior, processing, focus breathing and recording overhead are excluded unless explicitly modeled.
  • Use the displayed unit in every field. Ratios and percentages are different inputs; percent fields use values such as 25 rather than 0.25.

Frequently asked questions

How can I use flash guide number aperture calculator online?

Enter guide number m. Set distance m, ISO. Select Calculate and check the labeled output. Copy or download the JSON result.

Where is my input processed?

The bundled tool processes input in your browser. It does not upload tool input to a conversion service. Other site plugins, analytics, advertising and browser extensions may have separate behavior.

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