The EF 70-300 is the best way to get a lot of range without paying a lot of money.
It’s an EF lens, which means it can mount on both full frame sensor cameras (like the 5D) and cropped sensor camera (like the 7D).
At 70mm, it opens up to f/4, closing down to a maximum of f/5.6 as it zooms in. To compensate for the light lost by the shrinking aperture, the lens offers a highly evolved (third-generation) image stabilization system. Handheld, the IS on this lens allows you to slow your shutter speed down, effectively giving up to 3 additional stops of light. The IS on this lens features a dedicated panning mode, and as Steve mentions, can also sense whether the camera is on a tripod (meaning, unlike previous generations of IS, you don’t need to turn it off when it’s on a tripod).
For an additional $100 or so, you can pick up an EF 70-200 f/4 – instead of this lens. The 70-200 is a much more durable lens with better glass and a fixed aperture that will stay at 4 even when zoomed all thwe way in. So why isn’t it a no brainer? First, because the 70-200 is much heavier. Second, and more importantly, because that version of 70-200 isn’t image stabilized (the price for the IS version of the 70-200 f/4 is nearly double).
Partly it depends on which end of the range you’ll be shooting on. Between 70mm and 135 mm, the 70-300 will only stop down a half-stop. With the image stabilizer on, you’ll probably get a images as sharp as you’d get on the 70-200. Once you get in the 135-200 range, the 70-300’s image stabilizer is cancelled out by the closing aperture, and the 70-200’s images will probably edge out those of the 70-300.
And if you’re looking to to shoot beyond 200, there’s nothing to compare: of the two, only the 70-300 extends that far 🙂
From Canon USA:
The EF 70-300mm f/4-5.6 IS USM telephoto zoom lens has been developed to meet the high-performance standards that today’s photographers demand. Improved Image Stabilizer Technology provides up to three stops of “shake” correction, and the “Mode 2” option stabilizes images while panning with a moving subject. Compared to the original Canon EF 75-300mm IS zoom lens, this telephoto lens has faster autofocus, and overall the lens is lighter and has a smaller diameter than the original. The zoom ring can be locked at the 70mm position, making this powerful lens easy to transport, too.
|Focal Length & Maximum Aperture||70-300mm f/4-5.6|
|Lens Construction||15 elements in 10 groups|
|Diagonal Angle of View||34° – 8° 15′ (with full-frame camera)|
|Focus Adjustment||Front-focusing method with helicoid ring drive|
|Closest Focusing Distance||4.9 ft./1.5m|
|Zoom System||6-group helical zoom (rotational angle: 84°)|
|Max. Diameter x Length, Weight||3.0 in. x 5.6 in., 22.2 oz. / 76.5mm x 142.8mm, 630g (lens only)|