Having nothing better to do on my day off, reading some of the back and forth between the Canon 70-200 L and the Tamron 70-300mm and owning both the Canon 70-200 L non IS and the Tamron 70-300 4-5.6, I went outside and took some shots of a craggy tree I sometimes use for tests. All shots were hand held with a 7D and the Tamron had the IS on. The images were shot in raw and converted to jpegs. No sharpening or processing was used except for resizing for the web, which, unfortunately did create some image degradation, and it seems to me reduced the actual differences between the images compared to how they look on my local machine in non-uploaded form. People can decide for themselves which lens they find superior and by how much.
First is the Canon at f/4 at 200mm and below it is a 100% crop. Following those two are the Tamron at f5.6 at 218 mm and below that is a 100% crop of that shot. The Tamron goes to 5.6 at that focal length, other wise I would have matched the f stops. Below that is the Canon at f5.6 at 200mm followed by a 100% crop. Following that is the Tamron at f/5.6 at 300 mm followed by a 100% crop of that. I also have images at 70mm and around 135 mm, but due to posting limits they weren't included. I think if someone asks to see them I may be allowed to post them.
Canon f/4 200mm
Canon f/4 200mm 100% crop
IMAGE LINK: http://www.flickr.com …/64775760@N07/6560849251/
Tamron f 5.6 218 mm
IMAGE LINK: http://www.flickr.com …/64775760@N07/6560850111/
Tamron f 5.6 218 100% crop
IMAGE LINK: http://www.flickr.com …/64775760@N07/6560850187/
Canon f/5.6 200mm
IMAGE: http://farm8.staticflickr.com/7165/6560849301_49acd3266c_z.jpg
Canon f/5.6 100% crop
IMAGE: http://farm8.staticflickr.com/7035/6560849359_a620b83352_z.jpg
Tamron f5.6 300mm
IMAGE: http://farm8.staticflickr.com/7155/6560850989_7ef67ac771_z.jpg
Tamron f/5.6 300 mm 100% crop
IMAGE: http://farm8.staticflickr.com/7158/6560928033_5921d73666_z.jpg





