Lens Compatibility With The Built-In Flash - Pentax Q10 Operating Manual

210
Calculating Shooting Distance from Aperture Value
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 ÷ 6 *
Example)
When the sensitivity is ISO 200 and the aperture value is F2.0
L1 = 7 ÷ 2.0 = approx. 3.5 (m)
L2 = 3.5 ÷ 6 = approx. 0.6 (m)
Therefore, the flash can be used in the range of about 0.6 m to 3.5 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.
Calculating Aperture Value from Shooting Distance
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 3 m, the
aperture value is:
F = 7 ÷ 3 = approx. 2.3
If the resulting number (2.3, in the above example) is not available
as a lens aperture, a smaller number that is closest (2.0, in the
above example) is generally used.
10

Lens Compatibility with the Built-in Flash

Depending on the lens used with this camera, even if a lens without a hood
is attached, the use of the built-in flash may not be available or may be
limited due to vignetting.
The built-in flash is not available due to vignetting
03 FISH-EYE
* The value 6 used in the formula above is a fixed value
which applies only when using the built-in flash alone.
Lens Name