These shots were taken at the same time. The Canon lens was mounted on a 30D shooting RAW images. The Tamron was on a 350D set to the finest jpeg setting. Both images were edited. Perhaps this isn't a fair comparison, given that the Canon lens costs ten times as much as the Tamron and had a 120mm advantage due to the teleconverter. Nontheless, although the Tamron lens does a decent job, the image quality and resolution advantage of the 300mm f/4L is impressive here.