The optical image stabilization used on the SX100 IS is certainly one of the better systems we have tested recently. The camera has three modes: Continuous (IS on all the time), 'Shooting' (stabilization is only activated when the button is half-pressed to lock exposure) and 'Panning' (only stabilizes the effect of vertical camera shake, for photographing horizontally moving objects). Continuous mode makes framing easier - the system steadies the preview image - but obviously uses more battery power (it's on all the time).
The system makes handheld shots at 2 or even 3 shutter speeds slower than normal perfectly possible, although your hit-rate will decrease significantly once you get beyond that. The 100% crops below show the effectiveness of the IS system when shooting at full focal lengths at speeds as low as 1/10th sec.
|Real world example: 360mm (equiv), 1/10th Second, hand-held|
|Stabilization off||Stabilization on|
The stabilization test
In this simplified version of our SLR IS test, ten hand-held shots were taken of a static scene with the stabilization off and on. The shutter speed was decreased for each shot (from 1/500 sec to 1/15 sec). The zoom was set to its maximum position (360mm equiv.), the test target was 5 m away from the camera. The test was repeated 3 times and an average taken.
The resulting images were then inspected and given a blur score - 'Sharp' (no visible blurring at 100%), 'Mild Blur' (the kind of camera shake that is tolerable at small print sizes) and 'Heavy Blur' (virtually unusable due to camera shake) and 'Very Heavy Blur' (little discernible detail).
As the charts below show the IS system does give you a couple or even three stops advantage. At 1/50 (which is roughly three stops below the recommended minimum shutter speed (using the focal length reciprocal rule of thumb) you still have a 7/10 chance of getting a usable shot. And even at shutter speeds as slow as 1/15 sec 50% of shots are either sharp or only mildly blurred.
Hand-held, no stabilization (360mm equiv.)
As you can see from the chart below only at 1/250h sec or above can we be confident of getting sharp results from the majority of shots, and once you get to 1/50th sec and below the majority of shots are blurred, and none are sharp.
Hand-held, stabilization on (360mm equiv.)
With image stabilization activated the results improve significantly - you have a hit-rate of 100% usable images at all shots down to 1/125 sec. Even as shutter speeds as slow as 1/15th sec you have a one in five chance of getting a completely sharp and an 50% chance of getting an at least acceptable image.