I guess I'll add my inquiry here as well, if you have the current 70-200 2.8L USM IS, which for me is a bread and butter lens; sharp and fast as a tack, is there any advantage to upgrading?
As a nature / wildlife photographer, I don't see the sense in carrying around the heavy 2.8 version of this lens.
I do a good amount of event and commercial photography, and it is my main lens, as you mentioned.
I haven't read too many specs on the new lens, but have to assume it incorporates the updated IS mechanism, weight reduction, less CA, better coatings, and so forth. I find the 70-200/4LIS outperforms the 2.8IS, and look forward to upgrading.
The 70-200/4IS is lightweight, has great Minimum Focus Distance, so it's always in my bag in the field. I always dreaded carrying the 2.8IS, and thus rarely did.
For those with the new Mark4, there's another issue : with the 70-200/4IS you only get high-precision AF at the central AF sensor. With the f2.8 lenses you get to use 19 high-precision AF sensors. I tested both versions this weekend on the Mark 4 and there was a noticeable difference. But is the additional cost and weight worth it and how often will one really use the lens? If i planned to use the 70-200/f2.8 for a lot of BIF photography - perhaps worth considering, but for now I plan to just keep my 70-200/4IS.
Last edited by Peter Hawrylyshyn; 02-04-2010 at 07:01 AM.