Image stabilisation is a great feature to help your photography, especially with the longer lenses like the Sigma 150 to 500mm shown above, which I use for motorsport, air shows, medieval shows and nature shots where I can’t get too close to my subject. The best IS lenses can give an up to 4 stops advantage when shooting.
But these lenses need a certain amount of care when handling in order to avoid damage to the stabilisation mechanism. These lenses all work on much the same principal. A group of elements near the rear of the unit is held in position by magnets. A couple of motion sensors detect camera movements, and the circuit uses this part to make corrections, which ends up producing a much steadier image.
With what is effectively a tiny computer sitting loose in the lens, it goes without saying that care should be taken with it when attaching or removing the lens to or from the camera.
When you put the lens onto the camera and switch it on, the magnets are powered up and release the elements, ready to stabilise any shot you may take. It’s activated at the same time as the autofocus. But when the camera is switched off, the power to the magnet circuit is also switched of, which locks the floating elements in one place to avoid damage should the lens get knocked.
If the lens is removed before the locking has chance to complete, then the elements can move around thus leaving them susceptible to damage. So, the best way to protect you valuable investment in technology is to wait a couple of seconds after you switch off the camera, in order to allow the lens elements to lock into their safe position. Depending on make, some will give a click once that locking is complete, but some will have to done with judgement. But a couple of seconds usually does it.
Repairing lenses with broken IS units can be extremely expensive. You have been warned!