Well, this is my first L lens, so I'm not used to this kind of build and quality. But off hand I can say the IS on this lens works better than the 70-200 F4L, cos I was trying both lenses in the shop and this lens produced blur free images. Or it could be that this lens is sharper than the 70-200 F4L? :bsmilie:
For almost the same price, I'd take this lens over the 70-200 F4L seeing how the IS fares much better, so the drop in F-stop doesn't faze me that much.
Actually I believe the 70-300L uses the same 3rd generation IS system as the 70-200 f4L IS, providing up to 4 stop correction.. don't think the 70-300L is equipped with the HIS.
