You are all very helpful, thanks. I have looked at all the material you have refered and considered carefully your comments.There can sometimes bea fine line between getting 'something for nothing' and 'bang for your buck'. Without the opportunity to actually try before I buy, I don't know how close I am to kidding myself into thinking I can get 'something for nothing' (cheap lens reach with acceptable IQ).


The lack of opportunity to try one of these lenses will probably cause me to reconsider other options. For example: 70-200 f4 L + 2X extender would probably yeld better results while also greatly expanding my photo options. Cost may be higher but so is the re-sale. This combo will should also give more predictable IQ for someone such as myself that can't try lenses befor buying.


I also have a friend who is interested setting up a tripod on the beach and photographing his mates surfing, so he is looking on with interest.