a unique, heavy, short telephoto rectilinear prime lens with incredibly shallow depth of field (DOF) but this comes at a considerable cost in terms of price, weight, size and slow AF
two versions:
version I introduced in 1989
version II:
introduced in 2006
1.8x faster AF due to new CPU and improved AF algorithms (but still slow)
improved MF mechanism
improved lens coatings for less flare
it is one of the reasons to use a full frame camera rather than Micro Four Thirds system if you want this unique look
the 85mm f/1.2L II gives shallowest depth of field (DOF) and least flare but troublesome vignetting and long. CA
the Canon EF 85mm f/1.8 USM lens is much cheaper, gives sharp photos wide open with nice bokeh and is much faster AF but has troublesome lateral CA wide open