I really good J-3, pick of the litter, properly shimmed, is as sharp as a Nikkor 5cm F1.4 and Zeiss Sonnar. It's the sample-to-sample variation on the J-3's that is the issue. I've used (shot film) with about 20 J-3's. The best was as good as the Nikkor after being shimmed. Most of the ones from the 50s and 60s were close. The later lenses were not as good. The Nikkors and Sonnars do not deviate much sample-to-sample.