Im looking at trying to consolidate my lens options. At the mo, I use a standard 28-135mm f3.5, but when Im down by the thames, chasing zooming birds and documenting life on the river, I need something higher, at least 200mm. I tried a 400mm f4.5, but it was too bulky for anything other than planned trips. So, Ive just tried a 70-300mm f4, but again, a little too bulky for carrying round in a sling bag. Sigma do something like an 18-200mm f3.5 for the EF-S mount, but not EF. Anyone suggest an equivalent good versatile ' photojourno ' type lens for about town? I cant afford an 'L', dont need something superfast.