It's now a familiar story: Very fast lens, very small package. Where's the catch?
Here you go:
On the left, the RAW (CR2) file processed by Adobe Lightroom 2.5. On the left, the same RAW file processed in Canon's Digital Photo Professional (DPP).
Like the Panasonic LX3 which undoubtedly inspired its design, the Canon S90 has severe barrel distortion at its wide end. Completely expected but nonetheless disappointing.
