<span style="font-size: medium;"]Bill,


<span style="font-size: medium;"]I actually had the 24-105L before I exchanged for the 24-70L.


<span style="font-size: medium;"]By optically superior, the f2.8 is indeed a great deal for me. I shoot portrait and indoors; my experience shows that to go from f4 to f2.8 some time is the difference between "give-a-go" and "give-up", or between "nice blur" and "distracting background". Other than the aperture, the 24-70 has far less distortion at 24mm compared to the 24-105 - that sometime shows up on my landscape shots. The 24-70 @ f4 seems to perform a little bit better than the 24-105 wide open at comparable focal lengths (especially for contrast and vignette).


<span style="font-size: medium;"]Sharpness is something that I personally don't worry too much about as long as I'M USING A "L" LENS (which is an insurance for overall optical performance). I observe every parameter of my lenses from my real life shots not from just reading the ISO12233 results - because i believe what makes a lens a better performer is what it can deliver in real life. Don't get me wrong though, the ISO12233 charts that Bryan has been putting great effort in doing give me, in fact, everybody out here a great idea about which lens is sharp and which one is not so sharp. On the other hand, people looking at the charts and conclude (I always hear) that the 24-105 is sharper than the 24-70, the 70-200/4L IS is sharper than the non-IS 70-200/4L, etc... In practice, those difference in sharpness is something that's extremely hard for me to find and justify. It's not even because I don't pay enough attention on finding the difference in sharpness from my photos, it's just the matter that those difference in sharpness can be well ignored and you certainly will by no means get less sharp images if you choose one lens to the other. Choosing a 24-105 over the 24-70 because of the concern regarding sharpness does not make any sense to me, neither choosing the 70-200/4L IS over the non-IS model.


<span style="font-size: medium;"]I LOVE the IS on every lens that has it. It helps a lot when I handhold it to shoot. However, it's does nothing to stop your object from moving as you know. To me, to be able to shoot with a faster shutter speed in low light is more important, and I do need the extra stop background blur.


<span style="font-size: medium;"]I think it's personal to choose between the 24-70L and the 24-105L. Both are great lenses, depends on what you use them for. But in terms of optical performance, the 24-70 is the overall winner.


<span style="font-size: medium;"]Just my BS, no offence[]


<span style="font-size: medium;"]Benjamin