Sharpness at 17mm

For this test, the M.Zuiko Digital 17mm f/1.8 lens was attached to an Olympus E-PL5 camera, which in turn was mounted on a sturdy tripod. The self-timer was used in order to avoid any vibrations that may result from tripping the shutter. Slight tonal changes are due to slight changes in natural light during the session. The crops below represent 1/400th of the total frame area.

The full frame

In the frame centre, the lens is very sharp even wide open, although lens contrast is a wee bit low. Upon stopping down to f/2.8 contrast improves greatly, and sharpness peaks in the f/2.8-f/4 range. At f/5.6, the image centre is still extremely sharp, with f/8 still being very good. From f/11 onward, the effects of diffraction become highly evident, meaning you should usually avoid using the f/ and f/22 settings.

The border areas are OK but certainly not stellar when the lens is used at maximum aperture. Stopping down helps quite a lot, with results at f/2.8 and f/4 being remarkably good. The f/5.6 and f/8 settings are also eminently usable but again, diffraction takes its toll at f/11 and beyond.

Aperture	Centre Crop	Edge Crop
f/1.8
f/4
f/5.6
f/8
f/11
f/16
f/22