aperture - What are the benefits and costs of an image stabilized, slower lens vs a non-IS faster lens?

I am going thru a trade off decision between a 24-70 f2.8 lens and a 24-105 f4 IS lens from Canon. My dilemma is that the 24-105 focal length better matches my needs, but the f2.8 would occasionally be nice indoors.

What is the board's practical experience with IS? When comparing, at the same ISO and focal length, this trade off, one can observe that at f2.8 and 1/60th, would equate to 1/30th at f/4. In this example, is it practically possible to achieve blur free results with an IS equipped lens hand-held at 1/30th? (edit: this relates to the 24-70 range both lenses share)

Since it is fairly easy to achieve blur free images with nearly any lens at 1/60th and above, how does 1/30th with IS compare? Do you end up with sharp images at these speeds?

Answer

I can speak from actual hands-on experience here, for a change :) I owned both simultaneously; I kept the 24-105 and sold the 24-70. For ME, the benefits of IS outweighed the benefits of f/2.8 and the much better lens-hood of the 24-70. Your mileage may vary though.

The 24-105 IS allows me to shoot at 1/10 second at 105mm and expect a sharp photo. Or I can go to 1/5 and take three shots of every motive, and expect at least one to be sharp. With the 24-70 I'd have to live by the 1/focal length rule, exceeding 1/50 at 70mm would be iffy. The slow shutter speeds with the 24-105 lets me stop down quite a bit for depth of field for similar exposure as the 24-70 would give me at f/2.8. Extra depth of field is a Good Thing most of the time - I use the full-frame 1DsII so I don't get any free DOF from a sensor crop.

This, of course, only applies to stationary subjects. Which, fortunately, is what I shoot with the lens. In my experience, for moving subjects, the one extra stop that f/2.8 gives over f/4 is neither here nor there; if f/4 isn't fast enough then f/2.8 probably won't really cut it either. For low-light photography of moving subjects I take out the 85mm f/1.2L which is a portable black hole which will suck up any light that is present in the room. Candlelight is more than enough.

That said... the 24-70 was a more fun lens to use than the 24-105. It had a certain something. The 24-105 is a staid, practical, useful lens without a poetic bone in its body. Ho hum. The plain sister with the good personality, if you will. But it's the lens I use the most.