Olympus UPlanApo 10x0.4 WI - ultimate fun microscope lens
Apparently I am a fan of water immersion. Last time when I've got 10x0.3WI lens I thought I am set for life. But recently I've spotted even more interesting lens on ebay: Olympus UPlanApo 10x0.4 WI. That would be my first apochromatic microscope lens. It's very large field of view and 0.4 aperture makes it ~1.8x harder to achieve uniform focus over the field comparing to 10x0.3 WI. But the information density is again ~1.8 times higher.
In the center of the frame new lens (on the left) is sharper due to higher aperture (0.4 vs 0.3):
At the edge we can see that lateral chromatic aberations are lower for APO lens (who knew?). Remainng lateral CA is probably caused by microscope's tube lens. I surely correct lateral chromatic aberration in software, but this lens makes it easier and cleaner.