ISO speed coefficient

ISO100

ISO200

ISO400

ISO800

ISO1600

ISO3200

 

 

 

 

 

 

1

1.4

2

2.8

4

5.7

 

 

 

 

 

 

Photography distance range = Guide number × ISO speed coefficient ÷ Aperture

Ex) 35 mm-format or manual flash, power level: 1/1, focal length: 35 mm, aperture:

F4, ISO: 400

25 (Guide number) × 2 (ISO speed coefficient) ÷ 4 (Aperture) = 12 m The flash light reaches to 12 m.

When using the HSS flat flash (flash with HSS)

The flash range becomes shorter than that of normal flash photography when the high speed sync is used. You can get the correct flash range using the following guide number table and an ISO speed coefficient.

Guide number

35 mm-format or manual flash (ISO100)

Shutter speed

 

 

Flash Coverage Settings (mm)

 

 

 

 

 

 

 

 

 

 

16*

24

28

35

50

70

105

 

 

 

 

 

 

 

 

1/250

4.7

8.8

9.1

9.5

10.9

13.4

16.4

 

 

 

 

 

 

 

 

1/500

3.3

6.2

6.4

6.7

7.7

9.5

11.6

 

 

 

 

 

 

 

 

1/1000

2.4

4.4

4.5

4.7

5.5

6.7

8.2

 

 

 

 

 

 

 

 

1/2000

1.7

3.1

3.2

3.4

3.9

4.7

5.8

 

 

 

 

 

 

 

 

1/4000

1.2

2.2

2.3

2.4

2.7

3.4

4.1

 

 

 

 

 

 

 

 

1/8000

0.8

1.6

1.6

1.7

1.9

2.4

2.9

 

 

 

 

 

 

 

 

1/12000

0.6

1.1

1.1

1.2

1.4

1.7

2.1

 

 

 

 

 

 

 

 

* When the wide panel is attached.

GB50