AF Limiter - focus range limiter

introduction

many lenses offer a focus limiter switch which is designed to prevent the lens hunting throughout the whole focus range when trying to lock auto focus or have the camera ignore subjects outside of the selected range
Olympus with the Olympus OM-D E-M1 mark II have taken this a logical step forward and added such a functionality within the camera which can not only be applied to any compatible lens, but you get to specify the range from 0m to infinity with 0.1m precision
NB. currently it does not work with C-AF Tr mode (the camera may try to track on subjects outside the range that it can focus on) - use S-AF or C-AF instead.

in the menu, go to cogs, A1, AF Limiter
you get to set up to 3 preset ranges - just dial in the near and far distance in metres and make sure you leave the menu with it turned ON to one of the settings and you are done!

unfortunately, Olympus have not made an easy way to do this while in the AF Limiter setting, so here are your options

now this is cool albeit a little clunky to have to resort to
ensure AF Limiter is OFF and lens AF limiter is OFF
set AF mode to Preset MF and press INFO then you can AF on whatever spots you like and it will give you the distance read out on screen with 0.1m precision - just what you need for the AF Limiter!
see also: using preset manual focus on the OM-D cameras

the AF Limiter range generally does not need to be super accurate and entering in 10m to 50m may suffice - just test AF will work on the spots you need it to work on

AF on fainter stars can be a frustrating experience as the lens runs through the full range of focus distances trying to find maximum contrast.
You can address this issue superbly by setting the in-camera AF Limiter to something like 900m close limit and 999.9m further most limit (this essentially is treated as infinity by the camera).
Makes astrophotography sooo much easier!