Sony HVL-MT24AM Operating Instructions Manual page 39

Selecting the aperture when using other than ISO 100, or
when using the wide panel or diffuser
1 Check the calculated acceptable aperture under the same condition with
ISO 100 by using the table on pages 35 and 36.
2 Check the additional adjustment when using other than ISO 100 or
when using the wide panel or diffuser by using the table on page 38.
3 Select the calculated acceptable aperture by using the f/stop scale using
the results of step1 and step2.
Example: Using a 100mm F2.8 Macro lens, two twin flash units, no arm, a
power level of 1/4, magnification ratio of 1:1, ISO 200 with the
diffuser
1 Check the calculated acceptable aperture when using a 100mm F2.8 Macro lens,
two twin flash units, no arm, a power level of 1/4, magnification ratio of 1:1, and
ISO 100.
f/38 (refer to the table on page 36)
2 Check the additional adjustment when using ISO 200 and diffuser by using the
table on page 38.
Increase the aperture by +1.5 stops (refer to the table on page 38).
3 The aperture increased by +1.5 stops from f/38 is equal to f/22.