Sony alpha HVL-MT24AM Mode D'emploi page 55

Manual flash metering
Flash-subject
distance
The following explains how to obtain the aperture using the two twin flash units
with a power level of 1/1 at 1.5 m flash-to-subject distance and at ISO 100.
1 Draw a vertical line upwards from the flash-to-subject distance until it reaches
the flash power line that corresponds to the set power level ().
2 Draw a horizontal line leftwards from  until it reaches the vertical ISO line
corresponding to the camera used ().
3 Draw a diagonal line from  upwards and leftwards. The result indicates the
aperture that will provide the proper exposure ().
In this case, the proper exposure can be obtained by setting the camera's aperture
to f/16.
 The figures in parenthesis are employed when only one twin flash unit is used.
Flash power line Flash power line
1/1 1/1
1/2 (1/1) 1/2 (1/1)
1/4 (1/2) 1/4 (1/2)
1/8 (1/4) 1/8 (1/4)
1/16 (1/8) 1/16 (1/8)
1/32 (1/16) 1/32 (1/16)
1/64 (1/32) 1/64 (1/32)
(1/64) (1/64)