The optical image stabilization system used on the G10 works pretty well for most everyday photography - though don't expect miracles. There are three modes: Continuous (IS on all the time), 'Shoot only' (IS is activated at the moment the exposure is made) and Panning (for horizontally panned shots).
The first option makes framing easier - the IS system steadies the preview image, and we found it more consistently effective at extremes (where the shutter speed is more than 3 stops slower than would normally be used for the focal length you're shooting at) than the Shoot only mode.
Shoot only - which doesn't steady the preview image, but is theoretically more efficient because it minimizes the amount of corrective movement required by waiting until the instant the picture is taken - is perfectly effective when you're nearer to the correct shutter speed (and once you're within 1 or 2 stops it is actually more reliable). You may find you get different results than us; we have no quantitative tests for stabilization, and every person's 'shake' is different; users often disagree on which mode works best, so you just have to find which best suits your style of shooting.
We continue to be impressed with the IS system in the current G series camera. The good performance is really useful considering the results of the ISO performance tests later in this review, and the auto ISO setting on the G10 topping out at ISO 200. Most users will opt to have IS on all the time. It should be noted that despite the more secure grip on the G10, the form factor of the camera is more conducive to shake than more 'SLR-like' cameras, or digital SLRs.
These tests are rather extreme - up to four stops slower than you could safely use without IS - and in 'real life' shots - where you maybe using a shutter speed two stops slower than normal - the system is remarkably effective- as long as you support the camera carefully with two hands and don't try to 'grab' shots too quickly.
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 and repeated (from 1/125 sec to 1/2 sec). The zoom was set to its maximum position (140mm equiv.), the test target was 3 m away from the camera. The test was repeated three 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 about a three stop (almost four stops in continuous IS mode) advantage over shooting without IS, and even dropping down to four stops below the recommended minimum for a 140mm lens 90 percent of shots were sharp (again continuous IS mode).
Hand-held, no stabilization (140mm equiv.)
As you can see from the chart below even at 1/60th second it was possible to get just over half the shots taken to be completely sharp (This is a slight improvement over the G9, possibly due to the improved hand grip). By the time you get to 1/15th sec (two stops down from the recommended minimum) it's almost impossible to get a sharp - or even usable - result.
Hand-held, stabilization continuous (140mm equiv.)
With stabilization on the results are much better - we got no blurred shots at all at or above 1/15th sec, and the majority of shots down to 1/8 sec have little or no blur. Even down to 1/4 sec - an amazing five stops below the recommended minimum - 60% of the shots were sharp, so if you were to take 3 or 4 'safety shots' you'll get at least one completely sharp. This is very impressive IS performance.
Hand-held, stabilization single (140mm equiv.)
The IS single shots produced similar results to IS continuous. Again at or above 1/15 all shorts were sharp. Below that the results were slightly better than that of IS continuous. The variance can be down to user error, as every time you press down on the shutter button the movement of your body can be different, effecting the end result. The thing to take away from our IS test is that the G10 can produce sharp results at shutter speeds three stops lower than the recommended hand held with IS turned on.