thnx, yeh that sigma looks nice, I'll be doing all kinds of photography, including riding photophotography.
yeh i trying searching now too, though that sigma looks like exactly what i want...
yeh so you recken i need 200mm lense then? Bear in mind i won't just be taking riding photos. and I don't relly want to carry around any spare lenses so what everything i want in 1 lense preferably....
There's always a trade off and as a rule of thumb, the wider the focal range of a lens, the less the quality through the range. The flexibility generally trades off against lens speed (f/ stop), focus speed and sharpness.
There's no doubt that extra zoom range will add flexibility to the ability to take a shot. As to if it's needed or even better, that's up for debate!
I shoot wide most of the time, especially with bikes. Since I have just blown my budget (and more) on a new camera, I'll be 'stuck' with 17 to 55 mm for a while. This will do 95% of my photography - if I can't get the shot with the zoom, I'll look at it differently and recompose if possible.