Sony alpha HVL-MT24AM Mode D'emploi page 37

When twin flash units are at different power level settings
The values given in the preceding tables for the twin flash units assume that both
twin flash units are set at the same flash level.
When they are set to different flash power levels, the aperture needed for correct
exposure can be calculated using the following equation:
Aperture*
(A flash aperture)
=
Example:
Using a 100mm F2.8 Macro lens with a pair of twin flash units with no
arm, "A" flash is set at a power level of 1/8, "B" flash unit is set at 1/16, and
the magnification ratio is 1:1
The A flash aperture set at a power level of 1/8 is f/19 and the B flash aperture set
at a power level of 1/16 is f/13 (refer to the table on 36 page).
Apply these results in the above equation.
2 2
19 + 13 =
Therefore, in the above example, an aperture setting of f/22 will give proper
exposure.
* When both twin flash units are used.
+ (B flash aperture)
2
361 + 169 = 530
2
22
Continued on the next page