for the Round-2 test, for the copy I had and the test conditions
what I observed are:
AI 50/2 is a little lower contrast compare with Ai/AIS 50/1.8 @f2, and it makes the Ai/AIS 50/1.8 longnose looks a little sharper
but 50/2 wins in the image quality of extrme corner
AIS 50/1.8 japanese pancake version(full metal) @f2 is worse compare with 50/2
Ai 50/1.8 longnose is almost identical with AiS 50/1.8 longnose at f2
Micro-nikkor 55/2.8 is better than AF-D micro-nikkor 60/2.8 when full open, surprised me!
final funny one
Micro-nikkor 55mm f2.8 vs Russian Industal 61 L/M MC at f2.8
Industal-61 is Tessar optic structure, I was love this small lens very much until I met the Micro-Nikkor 50/2.8 "eagle eyes", from today's test, we can see 55/2.8 is really sharp even fully open