Inspired by the thread here http://www.fourthirds-user.com/forum...ead.php?t=7449
discussing the 14-35 Zuiko Digital and the Sigma 18-50 f/2.8, here are some test shots that show the Sigma is rather soft at 50mm although it sharpens up nicely at mid and wide focal lengths:
Sigma 18-50 f/2.8 - @ f/2.8 and 50mm
Sigma 18-50 f/2.8 - @ f/4 and 50mm
Olympus Zuiko Digital 12-60mm f/2.8-4 @f/4 and 49mm
Sigma 18-50 f/2.8 - @ f/2.8 and 25mm
Sigma 18-50 f/2.8 - @ f/2.8 and 18mm
The crops shown here are from the centre of the frame.