Sony alpha HVL-MT24AM Mode D'emploi page 34

Selecting apertures and power level in
manual flash
 The following tables show the values when ISO 100 is used without the wide
panel or diffuser. For other ISO speeds, or if you use the wide panel or diffuser,
adjust the aperture settings according to the table on page 38. When using the
twin flash units, the data assumes that the power lever is the same for both units.
If they are set at different power levels, see page 37.
 The aperture values given in the tables are calculated values. The actual lens will
have its own usable aperture range.
Example: Using a 50mm F2.8 Macro lens when ISO 100, with a pair
of twin flash units with no arm, power level of 1/1, and a
magnification ratio of 1:1
 The aperture is calculated at f/90 (refer to the following table).
 These following tables show the apertures where the proper exposure of the
illuminated area is obtained. Actual exposure varies according to the subject's
shape or position (p. 53). Test photographs or bracketing is recommended
especially when the subject is illuminated from side or behind.
 The following tables show data for certain lenses and magnification ratios. For
other lenses and magnification ratios, see page 55.

However, the smallest actual aperture possible with this lens is
f/32.
Therefore, if you set the power level to 1/1, the picture will be
overexposed.
But if you set the power level to 1/8, you will get a correct
exposure at f/32.