I do want another lens for my camera, a Canon EOS 400D. I know I have posted about this before. Sorry! I am looking at 2 lenses, both have their relative merits, but its a case of working out which has merits which are most significant. I want to be able to take better photo's at trackdays etc and get up closer to the cars.

Lens 1.

Canon EF 70-300mm f/4-5.6 IS USM

http://www.camerabox.co.uk/product1.asp?ProductID=4202

This lens obviously has the longer focal length of the two and is Image Stabilised, but the 'f' value range isn't as good (I think, not that I have a clue of the relevance LOL).

Lens 2.

Canon EF 70-200mm f4L USM

http://www.camerabox.co.uk/productDA...ProductID=2282

I don't think there is any doubt that this lens is better quality, but would the difference in quality (that I would notice) offset the fact that it lacks focal length compared to Lens 1? Does the f4L aspect mean that it is f4 across the whole focal range? Where the other lens is f5.6 at its maximum length? Or am I barking up the wrong tree?

Do you need 300mm of focal length to take the types of photo's that I want? Like this....



(Photo taken by Matt Woods)

Both lenses are similar money and to be honest, I really don't want to spend more than that. I'd prefer not to spend that much really, but I do want a decent lens too.

Discuss. (Please!!).