Nikon SB-5000 Bedienungsanleitung PDF herunterladen (Seite 171)

H-6

Tips on Speedlight Care and Reference Information

En-01

Guide Number, Aperture and Flash-

to-subject Distance

The guide number (GN) indicates the amount of light generated by a flash

unit. As the number increases, the flash output becomes greater and the

light extends further.

There is a relation represented by an equation, guide number (ISO 100, m/

ft) = flash-to-subject distance (m or ft) × aperture f-number. The SB-5000’s

guide number is 34.5/113 (ISO 100, m/ft, zoom head position: 35 mm, FX

format, illumination pattern: standard, temperature: 23 °C/73.4 °F). When

ISO sensitivity is 100 and aperture f-number is f/8, the illumination of the

SB-5000 reaches 4.31m (14ft), which is determined by the equation, flash-

to-subject distance (4.31m or 14 ft) ≈ guide number (34.5/113) / aperture

f-number(8).

• For ISO sensitivities other than 100, multiply the guide number by the

factors (ISO sensitivity factors) shown in the table below.

ISO 25 50 100 200 400 800 1600 3200 6400

Factor 0.5 0.71 1 1.4 2 2.8 4 5.6 8

• See “Specifications” for more details (0H-25).

t Determining aperture and flash-to-subject distance for

correct exposure

Aperture f-number

= guide number (GN for ISO 100; m or ft)

× ISO sensitivity factor / ash-to-subject distance (m or ft)

Flash-to-subject distance (m or ft)

= guide number (GN for ISO 100; m or ft)

× ISO sensitivity factor / aperture f-number

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Nikon SB-5000 Bedienungsanleitung Seite 171