The folks behind the Imaging Resource web site have launched a new site that focuses on the testing of lenses for digital SLR cameras. Utilizing DxO Analyser and some custom graphing software, the results at slrgear.com for the lenses they've tested so far provide an interesting glimpse into the optical capabilities of Canon, Nikon and other makers' glass.
The site's database contains many lenses for which no test data has been published as yet; those entries marked (TESTED) contain information on a lens' level of blur (similar in concept to the better-known modulation transfer function (MTF) measurement of lens resolution), chromatic aberration, vignetting and geometric distortion at different apertures (and focal lengths in the case of zooms). As an example, the site's Blur Index for the Canon EF 50mm f/1.4 shows how lab testing can sometimes provide meaningful information about real-world performance. Our experience with this lens is that it's uniformly awful wide open in contrasty light but uniformly spectacular stopped down to f/8-f/11, and slrgear.com's testing demonstrates that unequivocally.
Be sure to read the How we test lenses, Interpreting the results and What our test results don't show pages to properly understand the data coming from DxO Analyser and how it's presented on slrgear.com.