CAMERA SENSITIVITY AND FLASH RANGE

A change in camera sensitivity (ISO) affects the flash range. The flash range depends on the aperture used:

ISO settingƒ/2.8ƒ/4.0

 

Low80

1.0 ~ 3.8m

/ 3.3 ~ 12ft.

1.0 ~ 2.7m

/ 3.3

~ 8.9ft.

100

1.0 ~ 4.3m

/ 3.3 ~ 14ft.

1.0 ~ 3.0m

/ 3.3

~ 9.8ft.

200 / Hi200

1.0 ~ 6.0m

/ 3.3 ~ 20ft.

1.0 ~ 4.3m / 3.3 ~ 14ft.

400 / AUTO

1.4 ~ 8.6m

/ 4.6 ~ 28ft.

1.0 ~ 6.0m / 3.3 ~ 20ft.

800

2.0 ~ 12m / 6.6 ~ 39ft.

1.4 ~ 8.6m / 4.6 ~ 28ft.

1600

2.8 ~ 17m / 9.2 ~ 56ft.

2.0 ~ 12m

/ 6.6

~ 39ft.

3200

4.0 ~ 24m

/ 13 ~ 79ft.

2.8 ~ 17m

/ 9.2

~ 56ft.

What is an ƒ-number?

An ƒ-number indicates the relative aperture of the lens and lets us determine how much light it lets through. But why does the number get bigger when the amount of light decreases? The answer is in the way it is written, ƒ/2.0, ƒ/8.0. etc. That means the focal length of the lens (ƒ) divide by 2 or 8. So a 100mm lens at ƒ/2 has a 50mm physical aperture (100/2) and at ƒ/8, a 12.5mm physical aperture (100/8). So the f- number indicates the size of the aperture as a fraction of the focal length of the lens.

The ƒ-number series was carefully chosen to make controlling exposures easy. In the chart, the aperture and shutter speed combinations give the exact same exposure. Notice how the shutter speed changes to compensate for the change in aperture.

ƒ/5.6

1.0~ 1.9m / 3.3 ~ 6.2ft.

1.0~ 2.1m / 3.3 ~ 6.7ft.

1.0~ 3.0m / 3.3 ~ 9.8ft.

1.0~ 4.3m / 3.3 ~ 14ft.

1.0~ 6.0m / 3.3 ~ 20ft.

1.4~ 8.6m / 4.6 ~ 28ft.

2.0~ 12m / 6.6 ~ 39ft.

f/2.8 1/2000sf/4.0 1/1000sf/5.6 1/500sf/8.0 1/250sf/11 1/125sf/16 1/60sf/22 1/30sf/32 1/15s

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