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

Question

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 1

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.

Answer 2

Well if you're just talking about motion blur from your handheld shakiness - pretty much all the modern IS/VR/OS designs handle 1-stop differences pretty well. 1/30th at 105mm might be pushing it, but most current IS designs handle a two stop difference well, especially if you're a somewhat steady person.

At the claims of 3-4 stops is really where things get questionable.

The big difference here is that IS will counter your movement, but not your subjects. If you're shooting anything moving (people), then more shutter speed is better than IS - obviously more shutter + IS is even better. No amount of IS will counter the movement of a moving person. If you're shooting landscapes, its not an issue. If you're shooting weddings and events, it may be.

You're also getting more control of depth of field at 2.8 vs 4.

Answer 3

I can back up rfusca's advice with a practical example. I went through a similar dilemma, looking for a short telephoto to shoot people at events where flash is not an option. My choice was between the newly released Canon 100 f/2.8L macro with a four stop stabiliser and the 'king of low light' Canon 85 f/1.2L. The 100 offers four stops of stabilization. From the dpreview test it can deliver 3 stops stabilisation on a regular basis. So taking the 1/f shutter speed rule, and doubling it for safety, without stabilisation I could shoot at 1/200s. Adding three stops stabilisation gets me to 1/25s with a decent margin of error.

The 85 f/1.2L has no stabilisation but is 2.5 stops faster, but I'd have to shoot it at 1/170s, and ultimately end up with less light than the 100. In the end the added DoF the 100 gives to cover slight focus errors (not to mention weather sealing and macro ability) lead me to get the 100.

However after a while of using this lens I found that people just move too much for 1/25s. I moved to 1/50s and still found movement a problem. I had to work really hard to time shots, and often the ones with movement were the most expressive. So I ended up buying* the 85 f/1.2L anyway (I kept the 100 for macro and still subjects).

One stop is a bit different to three stops but the same principals apply, if you want to shoot people, especially up close, there's no substitute for shutter speed.

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*did I say 'buy'? I meant I invested in this lens. Given the interest rates at the moment I'll probably make more on the lens in the long run!

Answer 4

Image stabilization is generally very useful, but a faster lens is a faster lens.

In addition to the usual niceties of having access to a slightly smaller depth of field and being able to increase your shutter speed by opening the aperture instead of increasing the ISO, this article from The Online Photographer on f/1.4 lenses touches on some of the reasons you might want a faster lens (paraphrasing):

1. You might end up with a brighter viewfinder, which could improve both auto and manual focusing
2. The faster stop is available if you need it for whatever reason
3. A faster lens stopped down might have better image quality than a slower lens wide open
4. Faster lenses are typically better built

The not-trivial trade-off is that faster lenses are generally larger, heavier, and more expensive than a slower lens.

So if you're desperate for more light, you're always needing a faster shutter speed, you're addicted to smaller depth of field, or you need the more robust build, go for the 24-70/2.8.

If you care more about lighter weight or your subjects aren't moving (thus, image stabilization will be more useful), the 24-105/4 might be better. You didn't mention how you'd be using the lens, but if you go with the slower zoom and you're occasionally desperate for light, you might consider supplementing it with some fast primes (for example, a 50/1.4 or 85/1.8) for when you need the brighter aperture.

Answer 5

Keep in mind that you might wish to use your lens with studio lighting. In which case shooting at f/2.8 will give you shallower DOF. You'll need ND filters on the lights since most will not turn down low enough to shoot at f/2.8. The flash will freeze any motion effectively.

However, if you're not looking to incorporate lighting, an extra stop from the 24-70 will do two things for you: help autofocus (central AF sensors are more effective at f/2.8 or faster) and give you shallower DOF. The DOF can bite you, though, if there's not enough light to focus, or if you suspect intended focus will be hard to achieve. If neither of these are a concern, you can shoot at f/4 and push your RAW development by a stop easily.

So, if 24-105 fits your needs but 24-70 offers only occasional benefits, get the 24-105 and if you really find yourself needing the 24-70 - rent it.