ddk2001 wrote in post #16805065
Thank you all for the quick responses. I'm still confused . . .
Maybe I need to be schooled in the pros / cons of the various lens. For example - what do I give up (if shooting outdoors) going from the 2.8 to the 4 (if anything)?
Why will the 70-200 F4 outperform my 22-250 - assuming I'm shooting in good outdoor light?
Let's say I'm also considering a Canon EF 100-400mm f/4.5-5.6L IS USM (used - around $1,000). Other than better zoom capability - how is this different from my Canon EF-S 55-250mm f/4-5.6 IS? Is the "L" a better lens all around?
To answer your questions:
With a f2.8 lens: the extra stop would allow you to shoot in poor light (evening, indoors) without raising your ISO as much as you'd need to do with the f4. If you're going to be using the lens outdoors in daylight, this aspect is less important to you. The f2.8 will also, in some situations, allow you to blur out backgrounds a bit more. The price you would pay for this is a lot of extra weight and bulk: the f2.8 lenses are very large beasts, much more so than the f4 lenses.
The f4 lens has much faster focusing than your 55-250. Your keeper rate should go up accordingly. The price you will pay is the loss of the extra 50 mm of reach, so you might have to crop more (the same applies to the f2.8). If you choose the version without IS, that's another loss that you need to consider.
I used to own a 70-200 f2.8 non-IS, which I bought for sports, but I sold it for two reasons: weight (I hated it) and lack of IS. I replaced it with a f4 IS and was much happier. For outdoor sports during daytime, the f4 IS does an outstanding job, and the IS makes it a more versatile lens for other uses. Having tried it, I would not now buy another lens in this focal range without IS.
Regarding the 100-400: the build is better, the lens is weather-resistant, and you'll get better colour and contrast rendition (the same applies to the 70-200s). The focusing is also much faster than your 55-250. The price of this is weight and bulk (this is a large, heavy lens, although hand-holdable), and also a push-pull zoom mechanism instead of a twist mechanism.
One lens not on your list is the 70-300L, which can be found used for around $1000. It's an outstanding lens in every respect. It will give you quite a bit more reach than the 70-200s, without the bulk of the 100-400, and the IS on this lens is just outstanding.
Bottom line: there's no perfect lens. You need to decide what features you want, and what you're willing to compromise on. Have fun with your choice!