Olympus PEN F 42mm f/1.2 Half-Frame

Olympus PEN F 42mm f/1.2 Half-Frame

This Pen F half frame SLR lens is not as small as the 38mm f/1.8, but is a full stop larger aperture. How does it perform?

The Olympus PEN F series lenses are compact lenses designed for a half-frame (135 format 35mm) film SLR, which conveniently enough is basically the same size as an APS-C digital sensor. The PEN F shot a vertical picture on a 35mm frame. The longer dimension was up and down on the film, this meant you had to shoot with the camera held vertically to get a landscape orientation shot.

Being a half-frame lens, it was designed with a much shorter flange distance than a traditional SLR lens, so the adapter on the NEX is only about 10mm thick, and an overall length is only 57mm with the adapter and lens (to mounting surface). The adapter also tapers down and the lens is only about 54mm in diameter. This is still noticeably, but not a lot, smaller than a 50mm f/1.4 lens and adapter from an SLR. This lens is going to be close in size to the upcoming 50 mm f/1.8 OSS which is 62 mm x 62 mm (about the same size as the compact Olympus OM 50mm f/1.8 with adapter). Given that this lens is 1 f/stop larger aperture, it is relatively compact.

The lens has 8 elements in 6 groups, and has an 8 bladed diapragm, with slightly curved blades. Even by f/2 it is looking fairly octagon. The minimum focus distance is a short 0.35 m (1.1 ft), and is dense at 255 g (9 oz). Filter threads are standard 49 mm (larger than other Pen F lenses).

Optical Characteristics

Please click on the tab you want to view. Only 1 tab may be active at a time.

Comments on the Results

This lens has very good center performance across the range, but also very strong field curvature. The charts above show the best values for sharpness achieved at each position. Focused for central performance, the corners will be very soft wide open. If you want across the frame performance at large apertures you will need to make a compromise between center sharpness and corner sharpness. However, by only f/2.8 has great resolution across the frame.

Distortion is very noticeable, but not extreme -1.6% barrel (numeric average for all apertures).

Lateral CA is not well controlled and is visible on shots. Longitudinal CA in the out of focus regions is noticeable at large apertures, but is pretty decent for this class lens.

Coma and astigmatism are fairly minor. There is noticeable optical vignetting (cats eye shaped bokeh and a spiral look to the bokeh) at large apertures.

Purple fringing is minor, but there is some visible wide open.

The lens is sensitive to flare.

Bokeh is subjective, and it does get harsh in some conditions, but overall I find it very pleasing. Not sure why it gets such harsh reviews online, as the bokeh of this lens is less questionable than the 38mm f/1.8.

Measured focal length at 1:53 magnification: 44mm

Pros and Cons

Bottom Line

This lens is special because the performance basically peaks at f/2.8. This is a large aperture for the level of performance. You can stop down more, but it doesn’t improve a lot, and the contrast jumps between f/1.2 and f/2, and also between f/2 and f/2.8 are very noticeable. The largest aperture of f/1.2 is best reserved for centered subjects with less detail, but it is acceptable for available light portraiture. The reason to use this lens over the 38mm f/1.8 is performance at f/2.8 and the extra f/stop of light for available light. It is higher distortion and higher CA. A 50mm f/1.4 from a full size SLR might be a better value, but sometimes an f/1.2 lens is nice, and this lens is still more compact if the adapters are considered.


The gallery images are © 2011-2012 Eric Tastad, and may only be used for personal evaluation of the lenses. You can visit the gallery and download all the images (hover over a single image and click download and all available).