With SLRs and my OM-D, I typically shoot with both eyes open, so that my left eye can remain aware of what's going on outside the viewfinder. I've noticed that while looking through the EVF of my E-M5 with the 12-40mm lens attached and set at 40mm, I get a nice stereoscopic image of objects visualized in the finder (i.e. 3 dimensionality because both eyes are working together, and the apparent magnification of objects matches closely enough that my visual system can fuse them). Interestingly the focus distance doesn't seem to matter. Anyway it's notable because I haven't experienced the same phenomenon with other lenses (Olympus 40-150mm at 40mm, Canon 40mm f2.8 on 5D). Not sure if it's something special about the 40mm focal length, the 80mm effective field of view, or the particular lens construction, but it's an interesting and pleasing effect while shooting.