I am researching some potential upgrades to my kit. I have three great primes that I love (28mm f/1.8, 50mm f/1.4, and 85mm f/1.8). But I find myself wanting to travel light (as in fewer pieces of equipment, not necessarily weight) a lot, so a decent zoom or two would really fit well with what I want to do. That being said, I don't want just any zoom. I have a 55-250 f/4-5.6 IS currently and it does ok but not really the image quality or low light capability that I want.
I also plan to get a used 5D3/4 in the next couple of years, so I want to stick with EF lenses rather than going EF-S. I had considered the 15-85 and the 18-135 but neither seem to answer all my needs.
When I get the 5D3, my wish list would include the 17 TS-E, 17-40 f/4, and the 70-200 f/2.8 IS II. Those are all down the road type purchases.
For now, I am considering the 24-105 f/4L IS (I and II) and the 24-105 f/3.5-5.6. That range is good for my needs on my 60D for now, and will also serve me well on the full frame later.
My thoughts:
24-105 f/4L IS I: statistically insignificant differences in image quality as the version II (potentially?), but light weight and smaller
24-105 f/4L IS II : best of the three, but heavy; not sure I'd want to carry it all day
24-105 f/3.5-5.6: almost as good as the f/4 above (according to many reviews I've read), more affordable, and much lighter. I might not have issues carrying this all day. Issues with low light versus the f/4.
Which would rise to the top of your list? Which lenses not on this list would be high on your list to consider?
Devils advocate, if I wanted to stay with a crop sensor lens (EF-S), which ones offer the closest image quality to the L series glass in a similar focal length range as above? Perhaps I am wrong in thinking none of the non-L glass comes close to the L glass in image quality.
Thanks!



