Sharpness at 25mm

For these tests, the Olympus 12-25mm f3.5-6.3 lens was attached to an Olympus OM-D E-M1 compact system camera, which in turn was mounted on a sturdy tripod. The self-timer was used to avoid any vibrations from pressing the shutter release. Slight tonal changes are due to slight changes in natural light during the session.

The full frame at 25mm

Centre sharpness is commendably high even wide open at f/2.8, with peak performance achieved at f/5.6. Diffraction kicks in at f/16 and gets worse at f/22. The corners are a little soft at f/2.8, with the best performance achieved at f/5.6.

Aperture	Centre Crop	edge Crop
f/2.8
f/4
f/5.6
f/8
f/11
f/16
f/22