Olympus G.Zuiko Auto-S PEN F 40mm f/1.4 OM on NEX 3
This is the middle of three compact standards from the PEN F system, how does this compact large aperture 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 47 mm with the adapter and lens. The adapter also tapers down and the lens is only about 46mm in diameter. This appears to be in the same barrel as the 20 mm f/3.5 lens, which is about 5 mm longer than the 38 mm f/1.8 and 25 mm f/4 lenses, but still nice and compact. Build quality is superb, with all metal construction, nice smooth focus and aperture ring. I find the front aperture ring easier to use than some of those next to the body.
Same as with other PEN F lenses, you can pull out (towards the objective element) on the aperture ring and spin it around so you can control in specific aperture numbers (f/1.4, 2, 2.8, 4, 5.6, 8, 11, and 16) or you can use f/stops relative from wide open (0, 1, 2, 3, 4, 5, and 6)
The lens has 7 elements in 6 groups, with a 5 slightly curved bladed diaphragm. The minimum focus distance is good at 0.35 m (1.1 ft), which is the same as the rest of the standards, and the weight is not heavy at 165 g (5.8 oz). It uses rangefinder standard filters of 43 mm.
Comments on the Results
The lens has good to excellent performance in terms of resolution and sharpness in the center, and corners don’t reach very good levels until f/4 or f/5.6.
The lens has noticeable barrel distortion, but is typical for an f/1.4 standard at about -1% barrel.
Lateral CA is noticeable, and high for this class of lens. Longitudinal CA is visible, and I see some purple fringing to the bokeh light shots. I have gotten more consistant on white balance on these, now setting it to the same thing for all lenses, so some of my older lens tests might be off in white balance on these. Lightroom 4.1 allows for correction of longitudinal CA and it does a good job, as long as you don’t overdo it and there aren’t strong colors behind the fringes that will desaturate.
Coma and astigmatism are fairly minor, but as with the others the bokeh is cut off due to mechanical vignetting (the bokeh circles are not circular in the corners at large apertures).
Resistance to iris reflections is low, and veiling glare is high. Not resistant to flare.
Measured focal length is 42mm at 1:53 magnification.
Pros and Cons
- Center performance at all apertures
- Entire frame from f/5.6
- Small Size
- Corners at Large Apertures
- Field Curvature
If you shoot mostly at f/5.6 or 8 the 40 or 38 are probably just as good and better value. The 38 a little better across the field with less distortion and the 40 offering a little larger aperture. The 38 is the best wide open, but is also the smallest aperture wide open. Measured focal length on all of them at 1:53 are about 2 mm low, I measured them at 40, 42, and 44 respectively.
I don’t have a lot of extra to say about this lens, I would personally only get 1 of the 3 unless you are a collector, any of the 3 are good. All can have crazy bokeh in forested settings, so you just need to be careful and step down in those situations so the bokeh smooths up.