The PUMA with its improved lower collector Köhler system can deliver full Köhler illumination with objectives as low as x2 - as shown here:
I am unaware of any other microscope that can provide full Köhler illumination with full Abbe condenser down to as low as x2 so if you know of one I would be grateful if anyone can tell me (outside custom built instruments on optical benches). Thanks.
Field illumination curvature in both images above is exaggerated by the wide angle camera used to take these pictures via afocal projection through the eyepiece of both scopes. If you would like to see more details, the video explaining these upgrades to PUMA is on YouTube here: https://youtu.be/B0DOYpfdsyg
and the PUMA project page for all details and models is available here: GitHub - TadPath/PUMA: 3D Printed Microscope