Sony α7S III Gebrauchsanleitung Seite 17

The method for setting the exposure (shutter speed and aperture) in
the movie recording modes depends on the MENU 
[Shooting Mode]  [Exposure Ctrl Type] setting.
When [Exposure Ctrl Type] is set to [P/A/S/M Mode]:
MENU  (Shooting)  [Shooting Mode]  [Exposure Mode] or
Exposure Mode]  Select the desired exposure mode from among
[
P/A/S/M.
When [Exposure Ctrl Type] is set to [Flexible Exp. Mode]:
You can use the custom button to which [Av Auto/Manual Switch] or
[Tv Auto/Manual Switch] under [Auto/Manual Swt. Set.] is assigned
to switch between the automatic setting and manual setting for each
aperture value and shutter speed. If you select the manual setting, turn
the front/rear dial and set the desired value.
(C) Registration recall modes
Mode dial Shooting mode
1/2/3
Recall Camera Setting
Description
You can call up frequently used
modes and numerical value settings
that have been registered* in
advance then shoot the images.
* In [ Camera Set. Memory],
you can register various shooting
settings, such as the exposure
mode (P / A / S / M), aperture (F
value), and shutter speed.
(Shooting) 
GB
17
GB