it has the same field of view of a 90mm lens on a full frame camera and thus makes the perfect portrait field of view to avoid distorting facial features
it's wide aperture of f/1.8 allows a sufficiently shallow depth of field to make your subject pop from the background, this depth of field is similar to that of a 90mm lens on a full frame camera set at f/3.6
the lens has circular diaphragm blades to assist in giving nice bokeh when stopped down
it is optimised for movies with a silent AF and is one of the Olympus MSC designated lenses
it is a must have lens for Micro Four Thirds system users and at RRP $US399 is great value for money given that it seems to be sharper than the very expensive, large, heavy Nikon 85mm lens.
although presumably it does not have the incredible sharpness, flatness of field and macro capabilities of the Olympus ZD 50mm f/2.0 macro lens, it will give a similar field of view and ability to blur the background, but with much faster and more silent AF.
the Panasonic Leica-DG 45mm f/2.8 OIS macro lens offers the same field of view and with the addition of 1:1 macro capabilities and optical image stabilisation but at f/2.8 maximum aperture will not offer the same shallow depth of field and it is not optimised for silent, fast AF for HD videos.
although not on the Olympus website's compatibility table, it seems the Olympus Macro Converter will work on this lens which is very handy indeed!
45mm focal length = 90mm effective field of view
9 elements in 8 groups including two E-HR (Extra-High Refractive index) elements
7 circular diaphragm blades
closest focus 0.5m giving 0.11x magnification with long axis of subject ~13.5cm
use of Hoya Close Up filter #2 allows long axis subject dimension of ~9.5cm
use of Hoya Close Up filter #4 allows long axis subject dimension of ~5.5cm
internal focus so lens does not protrude on close focus
MSC designated fast and silent contrast detect AF capability for movies
37mm filter thread
front filter does not rotate on focus
metal lens mount
56mm wide x 46mm long thus easily fits in the palm of your hand
not as sharp in the centre as the incredibly sharp centre of the 12mm f/2.0 lens.
well controlled distortion, CA, and vignetting.
a very nice lens indeed for its size and price.
not as sharp wide open as the much more expensive combination of Canon 85mm f/1.8 on a Canon 5D Mark II but sharper than the Nikon 85mm f/1.4G on a Nikon D700 at f/2.0. It has less vignetting and distortion than either of these lenses at f/1.8-2.0.