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.
Sensitivity
Built-in
Flash
Guide
Number
Sensitivity
Built-in flash guide number
ISO 100
Approx. 13
ISO 3200
Approx. 73.5
ISO 200
Approx. 18.4
ISO 6400
Approx. 104
ISO 400
Approx. 26 ISO 12800 Approx. 147
ISO 800
Approx. 36.8
ISO
25600
*1
Approx. 208
ISO 1600
Approx. 52
ISO
51200
*1
Approx. 294
*1
This can be used when [3. Expanded Sensitivity]
in
the
[C
Custom Setting
1]
menu is set to [On].
Calculating Shooting Distance from Aperture Valu.e
The following equation calculates the effective distance
of
the flash.
Maximum flash distance L 1
= 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 100 and the aperture value is F2.8
L 1
= 13 + 2.8 = approx. 4.6 (m)
L2
= 4.6 + 5 = approx. 0.9 (m)
Therefore, the flash can be used
in
a range
of
about 0.9 m to 4.6
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.
Calcplating
•.•
Aperture
Value•·from··Shooting·oistance
The following equation calculates the aperture value for shooting distances.
Aperture value F = Guide number + Shooting distance
Example: When the sensitivity is ISO 100 and shooting distance is 4
m,
the aperture value is:
F
= 13 + 4 = 3.25
If the resulting number (3.25,
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.
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