The 24mm World Cup Final
Canon 24mm f1.4 L v Nikon 17-35mm f2.8 v Olympus 24mm f2.8
Chromatic Aberration Comparison
Even well stopped down, all but the very best retrofocus wide angle lenses suffer from (usually lateral) chromatic aberration. This is commonly manifest as blue/yellow or purple/green colour fringing wrapped around both sides of contrasty in-focus objects. Black on white transitions, such as brickwork or fine branches against cloudy skies, frequently cause problems, as they do to a greater or lesser extent for all our finalists. The following samples are screen shots from 200% views.
Even at f8, the Nikon zoom suffers from the blue flavour of lateral CA, whereas the Canon and Olympus primes have invasive reds and purples. In practice, the fringing is observable in many shots with the Nikon and Canon lenses, but you really have to go looking for it with the Olympus. Take for example these screen shots: the first are a detail at f5.6; the last one illustrates how much worse is the Canon 24mm's CA problem at f2.8.
The Nikon shows moderate blue CA around objects positioned at the edge of its image circle; the Canon suffers even more severely, as the following image shows, shot at f2.8:
It's very hard to make the Olympus misbehave in this way, so full marks to the Zuiko.