Pentax 12195 사용자 설명서

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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 *

* The value 6 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 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.

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.

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.

Lens Name

03 FISH-EYE