Sony FX 6 Quick Start Manual page 69

Exposure: AUTO Iris
There is no "one button" AUTO exposure mode with this
camera but that is not a bad thing!
When shooting video we don't want the camera to
randomly change shutter speed since this will change
how motion appears. The shutter should remain at twice
the frame rate unless you want a motion special effect.
Don't automate the shutter!
With video, auto exposure should ideally control the iris.
Put the IRIS on AUTO in the direct menu for this to
happen.
AUTO iris