Best bang for the buck...medium size zoom lens?

[Pascal]

The 70-200mm f4L IS is supposedly the sharpest of the 4 the OP lists. I have used the Sigma 70-200mm f2.8 NON-DG version and wasn't thrilled with it.

The advantages of smaller size and lighter weight are huge - especially when compared to the f2.8 L IS version. I used to own the 70-200mm f4 and now have the F2.8 IS. The IS helps and if I had to get another one, I would get the F4 L IS. For $960 or so, it is a sweet lens.

If you are going to use it strictly for low light (churches or sports or indoors), the f2.8 version will help with 1-2 stops at most - depending on how steady your hands are. If you are going with a tripod, then the f2.8 non-IS works well.

You can get a nice mint copy of the 200mm f2.8 L for around $500 if you look (forums or fleabay). A very nice lens - light and compact and easily handheld but limiting as it is a prime.

[crackhead]

the Sigma 50-150 f/2.8 is an underrated performer. Much lighter than the 70-200 2.8s and cheaper too. Consider it if you don't need the 151-200 range.

[lextalionis]

I'm on a budget and need to be mobile, so I vote for the 70-200 f4...I love mine...sample shots in my Lens Review Gallery: http://www.motleypixel.com

-Roy

[Donb10]

There is a 70-200mm f/4 IS listed in the buy and sell section. At the listed price I'm surprised its still there.

[Tom]

I paid 575 for my Sigma 70-200 2.8 in LN condition. Easily the best value. I have had tremendously great experiences with all my Sigma lenses.