Seem to be posting rather often lately......
Looking at the 24-70 f/2.8L II with envious eyes - is it really so much noticeably better than other 24-70s and the 24-105s?
I bought the 24-105 f/4L back in 2010 and was very pleased with it on my 50D, but (more recently) not overwhelmed on the 80D and very disappointed on the 6D. So I bought the MkII, which had decent optics but terrible AF shift issues; I tried and returned two copies. Next I bought the Sigma 24-105 f/4 Art, which is easily the best of the bunch (the majority of the time), however it seems to lose some of its sharpness on the 80D (superb on the 50D and 6D however). I'm now left wondering if I should just bite the bullet and splash out on the 24-70 f/2.8 II, which apparently is the daddy in this focal length range. But I'm also wondering whether the results would be too much different to lenses I own/have previously owned? I'm also looking at the 24-70 f/4 L IS, which seems to get very mixed reviews (which tells me that Canon's quality control with this product differs wildly!).
Looking at DXOMark, the 24-70 f/2.8 II is the clear winner by quite a margin, but the Sigma isn't that far behind. The 24-70 f/4 and original 24-105 f/4 lag some way back, but the former is considered better. I know DXOMark compile only lab test results rather than real-world performance, but it's a decent enough reference. Add to this apparently impressive offerings from Tamron and Tokina and I'm swamped with choices, although with no clear path to personal satisfaction.
One thing I have noticed with all the lenses I've discussed above (with the exception of the 24-70 f/2.8L II, which I can't comment on) is that they often (but not always) produce a fine, whitish-grey fringing (specifically around the cockpit windows and the bottom of the nose-gear door) when used on higher megapixel bodies, such as the 80D and 6D. Anyone know what causes this, and if indeed it is a type of CA?