Pentax K-500 Guia De Utilização

252

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Relationships among the guide number, aperture and distance must be

considered when shooting with the flash to obtain a correct exposure.

Calculate the shooting distance or aperture value in the following way,

and adjust the shooting conditions if the flash output is not sufficient.

The following equation calculates the effective distance of the flash.

Maximum flash distance L1 = Guide number ÷ Aperture value

Minimum flash distance L2 = Maximum flash distance ÷ 5 *

* The value used in the formula above is a fixed value

which applies only when using the built-in flash alone.

Example:

When the sensitivity is ISO 200 and the aperture value is F5.6:

L1 = 17 ÷ 5.6 = approx. 3 (m)

L2 = 3 ÷ 5 = approx. 0.6 (m)

Therefore, the flash can be used in a range of about 0.6 m to 3 m.

However, the built-in flash in this camera cannot be used when the

distance is 0.7 m or less. When the flash is used at distances closer

than 0.7 m, it causes vignetting in the picture corners, light is

distributed unevenly and the picture may be overexposed.

Distance and Aperture when Using the Built-in

Flash

ISO Sensitivity

Built-in Flash

Guide Number

ISO Sensitivity

Built-in Flash

Guide Number

ISO 100

Approx. 12

ISO 3200

Approx. 68

ISO 200

Approx. 17

ISO 6400

Approx. 96

ISO 400

Approx. 24

ISO 12800

Approx. 136

ISO 800

Approx. 34

ISO 25600

Approx. 192

ISO 1600

Approx. 48

ISO 51200

Approx. 272

Calculating Shooting Distance from Aperture Value

K-500.book Page 252 Friday, June 14, 2013 2:29 PM