Lens comparisons

This lunchtime I popped down to a local second-hand camera shop - camera in tow. The objective was to do a comparison test between my everyday Sigma lens and a better quality Canon lens. In particular, I wanted to check sharpness and vignetting (dark triangles in the corner of the shot due to lens deficiencies). Unfortunately the tests confirmed my thoughts - the Sigma is pants. Here are the results (Canon on the left, Sigma on the right).

Sharpness - 300mm at f/5.6













Sharpness - 300mm at f/22













Vignetting test - 300mm at f/5.6













Not very promising - the vignetting or the sharpness of the Sigma.....