178
Using the Flash
5
Distance and Aperture when Using
the Built-in Flash
Relationships between the guide number, aperture and distance must be
considered when shooting with the flash to obtain a correct exposure.
Calculate and adjust the shooting conditions if the flash output is not sufficient.
*1 This can be used when [3. Expanded Sensitivity] in the [A Custom Setting 1] menu is set
to [On].
The following equation calculates the distance of the flash for aperture values.
Maximum flash distance L1 = Guide number ÷ Aperture value
Minimum flash distance L2 = Maximum flash distance ÷ 5 *
* The value 5 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 F4.0
L1 = 16 ÷ 4.0 = approx. 4 (m)
L2 = 4 ÷ 5 = approx. 0.8 (m)
Therefore, the flash can be used in a range of about 0.8 m to 4 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 closer than 0.7 m, it causes
vignetting in the picture corners, light is distributed unevenly and a picture
may be overexposed.
The following equation calculates the aperture value for shooting distances.
Aperture value F = Guide number ÷ Shooting distance
Example)
When the sensitivity is ISO 200 and the shooting distance is 5 m, the
aperture value is:
F = 16 ÷ 5 = 3.2
If the resulting number (3.2, in the above example) is not available as a
lens aperture, the smaller number that is closest (2.8, in the above
example) is generally used.
Sensitivity
Built-in Flash
Guide Number
Sensitivity
Built-in Flash
Guide Number
ISO 100 *1 Approx. 12 ISO 3200 Approx. 64
ISO 200 Approx. 16 ISO 6400 Approx. 96
ISO 400 Approx. 24 ISO 12800 *1 Approx. 128
ISO 800 Approx. 32 ISO 25600 *1 Approx. 192
ISO 1600 Approx. 48
Calculating Shooting Distance from Aperture Value
Calculating Aperture Value from Shooting Distance
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