There are currently two prevalent kinds of image stabilisation being offered right now in the market, lens-shift image stabilisation and in-body sensor-shift image stabilisation. While both forms of stabilisation essentially deal in the same line of work, it's not necessarily correct to equate them as being entirely the same thing. As both methods of image stabilisation go about achieving results in a completely different manner, slight differences exist in their effectiveness and the question is, who does it better?

Optical Image Stabilisation: The Clear Winner?
Between the two, the general consensus states that optically stabilised lenses are the more superior kind of image stabilisation. Backed by the opinions of major camera manufacturers like Canon and Nikon, it is opined that since lenses are able to make small shifts in its optical elements to counter against large deflections of the image, they are much more capable at handling a wider range of turbulence. Moreover, besides stabilising the image on the sensor, it also stabilises the image seen through the viewfinder and further allowing users to see a much clearer view.

Sensor-Shift Image Stabilisation: Equally Effective?
In contrast with in-body sensor-shift image stabilisation, motion is detected through motion sensors inside the camera and directs the imaging sensor to respond by constantly readjusting its position for a much steadier shot. This works well to a large extent and perhaps even excellent when shooting with wide-angle to normal telephoto lenses.

However, the effectiveness of it gradually becomes limited or drowns when escalating up to the longer telephoto lenses (at focal lengths from 200mm and up). In Canon's Rebel XTi (400D) White Paper, Canon provides the example that a 300mm lens would require moving the sensor (APS-C size) about 5.5mm to achieve image correction, which claims is beyond the capabilities of current technology. Although, in Sony's recent A900 DSLR, it has managed to incorporate sensor-shift stabilisation to an entire full-frame sensor which does challenge this statement somewhat.

Down, But Not Out
Despite the limitation of in-body image stabilisation, don't be so quick to call it inferior just yet. If your photography deals mostly in the wide-angle to normal telephoto ranges, in-body stabilisation proves just as effective in preventing blurs. Even when you find yourselves using focal lengths from 200mm and up, wouldn't you be using a tripod or monopod to steady your camera instead? This would negate the need for image stabilisation tech altogether.

If that's not enough to make a case for in-body image stabilisation, let's not forget about its major advantage here. Any lens you wish to mount on to your DSLR, stabilised or not, you'll still be protected with a degree of stabilisation. With stabilised lenses generally costing more than those without, you'll be saving yourselves a pretty penny by opting for the non-stabilised versions and getting stabilisation from the sensor. You can further reap the benefits especially with lenses that don't specifically come in image stabilised versions.

So, Who's the Winner?
The fact of the matter is, optical image stabilisation is still theoretically the better kind of image stabilisation available. Since no matter what focal range you decide to use, this method assures you of effective stops to blurring. On the same breath, we shouldn't interpret this as a reason to shun in-body image stabilisation as it's still proven to be effective at most focal ranges and more importantly, their convenience is something to be acknowledged. Perhaps improvements are underway but at current, Canon and Nikon have chosen to distant themselves with in-body image stabilisation, while Sony, Pentax and Olympus have all released DSLRs featuring this form of image stabilisation.