|
I recall reading a while ago a rule of thumb - the bigger the zoom range, the lower the quality of image. Broad brush statement, but I think what it alludes to is that it's hard to manufacture a lens that's sharp across such a range of focal lengths. Usually they have a sweet spot somewhere. Maybe the comments were based on "pixel-peepers" and in the real world you may not notice the difference. Not sure.
Another thought - check that you'll still get autofocus. If memory serves, you need at least f/5.6 wide open to get AF on Canons? So at the 600mm end where it's f/6.3 wide open, you may not get AF to work and will be forced to manual focus. Not sure, just make sure you check.
Should point out that comment above is nothing against Sigma. I have 2 Sigma lenses and they're great - among the sharpest lenses I have. I would have made the same comment about Canon-made lenses. I have the Canon 100-400 and don't reckon it's anywhere near as sharp as the Canon 400/5.6.
|