I have been doing a bit of research on the design of this lens. It is a 1920's design, one of the Ernostars designed by Ludwig Bertele. The main characteristic of this asymmetrical design is the three large front elements. He then went on to design the Sonnar in which two of these elements are replaced by a cemented triplet. In the days before lens coatings this increased contrast (by removing glass-air surfaces) while allowing control of high order aberrations. Once coatings were developed, this was not so much of an advantage. The OM 85mm is quite like the current Zeiss ZM 50mm f1.5 Sonnar in that they both have the three separate Ernostar-like front elements. The rear groups are different: a cemented triplet for the Zeiss and a cemented doublet for the OM . It appears that even Zeiss have decided that the front cemented triplet is no longer necessary but I imagine their rear cemented triplet (as opposed to the cemented doublet of the OM) is necessary for Zeiss to control the high aperture aberrations. The OM 85mm is very like the current MS Optical 50mm f1.3 Sonnar (i.e. 5 elements in 4 groups). It appears that lens manufacturers are reluctant to revive the 'Ernostar' name, even though it is historically accurate, preferring to keep the name 'Sonnar'. Both these Sonnars are noted for the sonnar 'look' in particular a smooth bokeh. The Zeiss Sonnar suffers from focus shift i.e. a change of focus with aperture. Zeiss state that this problem is intrinsic to sonnar designs which do not have floating elements so the only way to overcome the problem with their lens is to compensate in some way at the time of taking the photo. Several of the Olympus OM lenses (e.g the 85mm) are based on German designs but Olympus, rather than simply copying them, seem to have tried to improve on them. One point before discussing the design: why 85mm? It's not possible to design a 50mm sonnar for an SLR -there's not enough room for a mirror behind the lens. Obviously 85mm is OK. Olympus designed their 85mm with floating elements in order to control high order spherical aberrations at close focussing distances. Using a ruler to measure the axial movements of the lens, it's apparent that the lens moves as a unit when focussing from 0.85mm to about 10m but the distance between the front and rear groups increases by about 0.5mm as the lens is focussed from 10m to infinity. I have never noticed any focus shift with my OM 85mm so it appears that this correction has done the trick. Olympus managed to patent this feature. In the same patent they explain that flotaing elements also have the advantage of controlling aberrations at full aperture: in particular coma becomes more symmetrical. They claim therefore that the soft focus effect at full aperture is particularly pleasing i.e. it can be particularly good for soft focus full aperture portraits. My OM 85mm is indeed a little soft at full aperture; its particularly sharp at f2.8 and only really recovers this sharpness by f8. I tend to use it from f2.8-f11 and I've never particularly noticed the sharpness (or relative lack of it) in a print. What I do notice is a particularly smooth bokeh. Accorrding to current usage of the name, it really does deserve to be called 'the OM Sonnar'.