Oldoc,
Cron IV is usually compared to UC-Hex 35/2 (or the other way around) since they have similar size, similar optics, etc. UC-Hex focuses down to .9m, while cron - down to .7m. Now, this is not to be confused with M-Hexanon 35/2 - which is larger - looks very similar to Summilux sizewise. M-Hex focuses down to .7m also and draws more like Lux IMO.