Sony HVL-MT24AM Manual De Instrucciones página 26

Selecting Apertures in TTL Flash
 The following tables show 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 tables on page 28.
 The aperture ranges 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, at a magnification ratio of 1:1
 The range of acceptable apertures is calculated to be from f/4 to
 The following tables show data for certain lenses and magnification ratios. For
other lenses and magnification ratios, see page 54.

f/90 (refer to the following table).
However, the lens aperture range is f/2.8 to f/32, so the actual
range possible with this lens is f/4 to f/32.