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keisanHigh-precision calculations for everyday life and work

Aperture settings for taking clear photos with a flash

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Calculates the optimal aperture value (f-number) based on the flash intensity when taking a photo.
Number of flashes
個
Flash (GN)
ガイドナンバー
Distance (d)
m
Film Sensitivity (ISO)
Aperture Value (F-number) The smaller it is, the more light it captures
Guide Number

(GN) is a measure of flash output. It is expressed as the product of the aperture value (f-number) and the shooting distance (in meters) required to achieve proper exposure at ISO 100.
Film sensitivity

(ISO) is a measure of a film’s sensitivity.The
aperture value

(F-number) is a measure of a lens’s brightness, calculated by dividing the lens’s focal length by its effective aperture.

Exposure Calculation Using Guide Number (GN)
\(\\ \hspace{30px}F=\frac{GN}{d}\sqrt{\frac{ISO}{100}}\\\)


For multi-flash setups, GN’ is calculated using the following formula:
\( \hspace{30px}GN'= \sqrt{(GN_1)^2 + (GN_2)^2 + \cdots (GN_X)^2} \)


This applies when flashes are fired from the same position and in the same direction.

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