So i was bored and thought i'd do some comparisons of MTF charts from www.photozone.de
all in one go.
efs 55-250, currently â‚¬220
ef 100-300, â‚¬320 (nearly a 55-250 plus a niftyfifty) (nb this one reviewed on the 350d)
ef 70-300 nonL, â‚¬470 (2x the 55-250)
ef 70-300L, â‚¬1350 (6x efs55-250 and a few crates of beer)
<well yeah, i did have a chart here, was just a screenshot comparing the MTF charts of the above 4 lenses side-by-side>
ok, so the focal lengths aren't all exactly the same, but here's my conclusions:
widest end, all fairly similar, maybe the 70-300 non-L is the loser. the 55-250 @ 250/5.6 is almost touching the L @70/5.6 in centre resolution. (100-300 is probably out-resolving the 350d it was tested on).
at 135mm the 55-250 is down a bit on resolution (but barrel/pin is almost nothing)
200mm, you get what you pay for, although the 2 cheapest lenses are roughly the same if you average centre/corner.
longest end gets interesting, the 100-300 falls apart, but it is the oldest. 55-250 beats the 70-300nonL. The L wins of course, but not by much at the longest end.
So coming from someone who doesn't own the 55-250 (i did own the 70-300 nonL and just upgraded to the L), i'm going to say i'm impressed for what it can do, for the price. But then, i'm also impressed with the newest 18-55IS kit lenses (given that they're the same price of a niftyfifty, which i also own and love).
<i also thought i had a comment about how canon did get a lot of flack for their first kit lenses, check the MTF of the first 18-55 non-IS models. but they've definitely made up for lost ground with the latest 18-55 IS, as well as the res of the 55-250>
and back to the USM vs non arguements, i think if you gave joe average who'd only ever used a point and shoot the option, faster focussing, sharper pictures, or both for a higher price, i'd say there's a fairly good chance he'd go for the sharper pictures (hey, i would too, normally).
my old point and shoot took about 2 seconds to focus every time. both the 50/1.8 and 70-300 non-L were blazing fast compared. between those two stepping up to the efs15-85 and 70-300L ringusm lenses, the difference is noticable (definitely quieter, and the speed is just noticably faster).