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ADVANCED OPERATION FOR THE BUILT-IN FLASH
4.Metered Manual Mode
•When using the
1.Calculating the flash effective range according to the camera-
Maximum flash distance = Guide Number ÷ Selected aperture Minimum flash distance = Maximum flash distance ÷ 5*
✍MEMO
•When the distance to the subject is less than 0.7m (2.3ft), the flash cannot be used. If the flash is used less than 0.7m, it causes vignetting in the picture corners, light is distributed unevenly and the picture may be over exposed.
•*The value 5 used in the formula above is fixed value applied to the
The guide number (GN) depends upon the film speed used as shown below.
ISO25 |
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| GN5.5 | ISO200 |
| GN15.6 | |
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ISO50 |
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| GN7.8 | ISO400 |
| GN22 | |
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ISO100 |
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| GN11 |
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Exp. If an ISO100 film is used at an aperture of f/3.5, the flash effective distance is obtained as follows:
For maximum distance Guide Number (11) ÷ f/3.5 = 3.14m For minimum distance 3.14 ÷ 5 = 0.63m →0.7m *
* Minimum distance of the
Thus, the flash effective distance is from approx. 0.7m to 3.14m.