##From the manual, no aperture limitation?##
The manual of the Olympus OM-D E-M1 Mark II doesn't provide any hint about aperture limitation when using High Res Shot. The dedicated section can be found page 48 and page 99.
The only parts related to High Res Shot's limitation can be found at the following pages:
- Page 91:
Bracketing can not be combined with HDR, interval-timer photography, digital shift, multiple-exposure photography, or high res shots.
- Page 97:
The following is not available while keystone compensation is in effect : [...] High Res Shot
##From Internet: no aperture limitation !##
This website gets more in depth about how the High Res Shot mode works. Aperture is mentioned 13 times, mostly about focus shifting issues when stopping down a lens BUT, in the commentary you can read:
With native lenses you are limited to f8 or wider, legacy lenses can be used at whatever aperture you like of course.
So it seems that legacy lenses can be used!
This page says, when using High Res Shot mode (lens not mentioned):
No aperture we tried (from f/2.8 to f/8) was able to begin resolving any of dots with the E-M5 II, so diffraction limiting is not to blame.
So it confirms that High Res Shot mode is working at least from f/2.8 to f/8.