Olympus E-P1 Review: 23. Lens tests: Digital Photography Review

Studio Tests - M. Zuiko Digital 17mm F2.8 Pancake lens

The EP-1's second kit lens is the fixed-focal length 17mm F2.8 'Pancake'. At just 22mm long and 2.5 oz / 71g in weight, this is the smallest and lightest Micro Four Thirds lens, and fits well with the camera's compact concept.

UPDATE 9/24/09: Lens test data has been updated using the full release version of Adobe Camera Raw 5.5 for image processing. The results are essentially the same as from the beta version we used for original publication, and the conclusions unchanged.

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NOTE the line marked 'Nyquist Frequency' indicates the maximum theoretical resolution of the camera body used for testing. Whenever the measured numbers exceed this value, this simply indicates that the lens out-resolves the sensor at this point - the calculated MTF values themselves become meaningless.

The M. Zuiko Digital 17mm F2.8 Pancake gives acceptable results in our studio tests, but again its extreme portability comes at the cost of some optical compromises. Image quality at the centre of the frame is high, but it's less impressive towards the edges due to a combination of (relative) softness and chromatic aberration. Compared to the kit zoom, there's no hugely compelling optical advantage to the 17mm (although it's faster and more portable), and overall its performance leaves us feeling just a little 'flat'.

Sharpness	Central sharpness is very good wide open, but the corners are distinctly soft. Stopping down improves matters, and best results are obtained between F4 and F6.3; however the corners lag behind the centre at all apertures. As usual with the Four Thirds sensor, apertures smaller than F16 are unacceptably soft for most applications.
Chromatic Aberration	Unlike Panasonic, Olympus is not correcting lateral chromatic aberration in software on Micro Four Thirds. This is unfortunate because chromatic aberration is rather high, with strong red/cyan fringing visible across much of the frame. Fringe widths also increase on stopping down, peaking at around F11.
Falloff	We consider falloff to become perceptible when the corner illumination falls to more than 1 stop less than the centre. There's just a little falloff wide open (1 stop), that disappears by F4 - nothing to worry about.
Distortion	Geometric distortion is being corrected in software, but again not quite completely - our tests reveal a little residual barrel distortion (0.9%). This shouldn't be visible in most shots, but could show up in the occasional highly geometric composition.

Macro Focus

The measured closest focus distance is an impressive 0.16m, (compared to Olympus's specified 0.2m), which gives a working distance of about 11 cm between the subject and the front of the lens. But this being a wideangle, that doesn't translate to a particularly small image, and magnification is just 0.15x.

Image quality is OK; the centre is sharp at F2.8 but, mirroring our studio tests, corners are very soft, and don't properly sharpen up until about F5.6, with best results around F8 - F11. There's just a little barrel distortion, and some red/cyan fringing.

Macro - 119 x 89 mm coverage
Distortion: Mild barrel
Corner softness: Low
Focal length: 17mm (34 mm equiv)

Software correction of distortion

As with the 14-42mm, the 17mm F2.8 Pancake takes advantage of the Micro Four Thirds system's ability to correct geometric distortion in software. The comparison below illustrates the transformation from the highly barrel-distorted raw image to the properly-corrected final version.


Uncorrected (+ 4.2%)	Corrected (+ 0.9%)

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