I wonder what you make of this option on my new150-600mm ?
Here's the description from , about the use of the focus switch. I know you can depress the button halfway, let it autofocus, then tweak the focus manually using the focus ring - but this can be done when the switch is in the AF position. Don't see what MO adds to that.
...and then I can't make sense of the line "With AF position, standard full-time manual focus is available." except that it also seems to indicate the MO switch is superfluous.
In addition to AF/MF, MO (Manual Override) is incorporated as one of the options of the focus mode switch.
By setting it to the MO position, it switches to manual focus by rotating the focus ring even during continuous AF.
With AF position, standard full-time manual focus is available.
Using the optional USB DOCK, it is possible to adjust the MO position’s sensitivity to switch to manual focus.