Chromatic Aberration
Chromatic aberration, on an optical/technical level, occurs when different colors of light, refracted within a lens, do not precisely align at the plane of focus. The result is an unnatural, colored outline superimposed along the edge of objects in the frame. The artifact is particularly noticeable against solid backgrounds (such as the sky), and can be a difficult correction to make in post-processing; prepare to spend significant time removing it (even using the CA sliders in Photoshop).


We measured chromatic aberration on both Micro Four Thirds kit lenses by photographing an ISO Resolution Chart with an Olympus PEN E-P2 and Panasonic Lumix GF1 camera bodies, and analyzing the files in Imatest testing suite.


The graph below shows the chromatic aberration produced by each lens throughout its aperture range. As you can see, the optics maintain a nearly identical curve, producing increasingly more aberration when stopped down. Panasonic’s Lumix G Vario lens, however, shows consistently less chromatic aberration at all settings.
 

The Panasonic lens peaks with respect to chromatic aberration at f/8, while Olympus’s M.Zuiko lens performs best at f/6.3. However, even at its peak, the Olympus M.Zuiko lens produces over 50% more chromatic aberration than Panasonic’s counterpart. Mousing-over the image below, you can toggle between results from the two lenses, and see the broader dispersal of light from the Olympus lens. Note, in an ideal lens, the RGB lines would overlap perfectly.