i love the idea of screwing on a simple lens that will double my lenses power, the one i was looking at was one that ive seen go second hand on ebay but have found new for £101, its the kenko teleplus mc-7 which i found here -
http://www.microglobe.co.uk/catalog/...-for-canon-eos
my only lens at the moment that are under F4 are my tamron 90mm and the canon 50mm that i have coming in the enxt day or two. my two telephoto lens are both over F4, so maybe its not worth me spending another hundred quid right now