Thanks Geoff and Dai, though I think I may have given the wrong impression that I need a long lens. I have the Sigma 50-500 which does me fine for the long end of things and I have a Sigma 105mm for macro. So the lens I'm looking to buy here is to essentially cover 105-200mm (I think the Sigma is effective at 300mm). I can't foresee myself getting tangled up in extension tubes and/or converters, just the lens on its own.
I've found somewhere where I can get a f/4 with IS for little over £760. Is the F/4 with IS going to be much different to a f/2.8 without?
Why is it so hard to make decisions
