Getting a sharp photo is every photographer’s dream and to get there you can employ several methods. Traditionally these ranged from tripods, monopods, very fast shutter speeds and gernaly just getting your camera still.
There was, however, the problem that if you were on the move or did not have a fast f2.8 or faster lens, your pictures ended up blurry and unsharp because you moved. Human beings cannot stand perfectly still for a long time, i mean several seconds, and long(er) exposures did not go well without the proper equipment. But then came image stabilzation.
What it is
In a nutshell image stabilzation is nothing more than a few sensors in your lens or camera that detect small movement like from breathing or muscle twitch. The mechanism then calculates the mmovement and adjusts the lens or camera to compensate the movement and in so giving you a “stable” exposure and a sharp photo. Varying in implementations, the system can give a 2-4 stop reduction in shake. To put it in simple terms, if you shoot 100mm, to get a stable shot you should soot at 1/100th of a second. Well, with a 4 stop reduction, you could shoot at 1/7th or 1/8th of a second to achieve the same sharpness by reducing camera shake with a stabilizer. Remember each f-stop is half or double the light amount.
The problem is that there is no single great implementation and in different conditions they all are effective in their own right. There are also at least two different implementations up to today. The first is based in the lens, which is very common, and the second based in the camera through somthing called sensor shift.
1. In Camera
Consider the camera sensor as the puck on an airhockey board. It moves perfectly fluent in all directions. the same with the sensor shift technology. The camera detects the movement and the sensor is adjusted accordingly. This is great as lenses do not have to be modified or become more expensive and even your oldest manual lenses are optically stabilized. The following Manufacturers have in camera stabilization:
- Sony: SSS - Super Steady Shot
- Olympus: IS – Image stabilization
- Pentax: SR – Shake Reduction
2. In the lens
This is much more common nowadays and it is becoming almsot the de-facto standard features in new lenses, especially professional or “slow” lenses with an f-stop of 3.5 of lower. Basically it works the same as the sensor shift, except that it is some of the lens elements inside the lens that shift and move. The benefit here is costs are offloaded to the lens manufacturer and some clain this approach is more efficient. The cost of the sensor shift technlogy is also cut out from the camera cost, though you and I will never notice the cost difference for some weird reason (irony!).
Now different manufacturers call image stabilization differently and more and more third party lens manufacturers are building this into their lenses as well. Below is a list of what this is called form each manufacturer.
- Canon: IS – Image Stabilization
- Nikon: VR – Vibration Reduction
- Tamron: VC – Vibration Control
- Sigma: OS – Optical Stabilizer
Why you want it
Basically it gives you greater flexibility and an advantage in taking better pictures in more variable environments. So you might get a sharper shot in semi darkness without cranking the ISO too high. Some implementations give an advantage of up to 4 stops´and allowing you to shoot up to 1/8th of a second handheld with a resulting pinsharp photo. you can take the flash out of the equation and get a more natural shot etc. Overall there is not a good argument, besides the cost increase, NOT to have it.
Now on the side of cost increase, yes this thing costs more but even consumer lenses have, in some cases weaker but still efficient, implementations of image stabilization. Nikon’s cheap 18-55mm VR kit lens is stabilized and works extremely well for their entry level cameras, the same goes for Canon. Overall it is one of the best advances in technology for photography since the digital shift and if I can, I buy all my lenses with VR (Nikon). But please don’t solely rely on VR for sharp shots, leaning against a tree or stabilizing the lens/camera in any other additional way helps even further.
Please be aware that nikon and Canon both tell you to turn the feature OFF if you shoot on a tripod. The reason is that VR (or IS) will compensate and shift the elements any way and that will cause you blurry images shot from a tripod.
So in the end, Handheld= VR (IS, VC, OS etc.) while tripod = turn is all off! 
