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| p.1 #4 · p.1 #4 · To ugrade or not to upgrade, that is the question |
Having just recently upgraded from a 40D + 17-50 to a 6D + 24-105, I can say there was a dramatic difference in IQ. Both the change in overall quality and the change in DOF due to the larger sensor are huge. There will probably be a bit less of an improvement for you, because I think the T2i has a bit better IQ than the 40D, but it will still be there.
I also had the 70-200 with the 40D, and while it wasn't originally in my plan, I shifted my kit to the wide end, as I didn't find myself using the telephoto all that much. So now I have a 17-40, 24-105, 50/1.8, and 85/1.8.
Keep in mind that the 50 is an entirely different lens on full frame, I rarely used it with my family on my 40D, but I use it all the time with the 6D.
For family stuff, I don't miss the 70-200 much, the 24-105 gives me enough extra reach on FF compared to what my 17-50 did on crop. Of course, it will be almost exactly the same range as your 15-85 on crop.
I do plan to add a telephoto zoom eventually, but for the amount that I use it, I am considering getting the much cheaper, but still pretty decent 70-300 IS instead of one of the L teles.