The autofocus is fast and accurate. At the image quality are available at my copy nothing to fault. Of course, the light weakness is a certain shortcoming, but in this price range you can certainly expect nothing else. And even in the evening light go out of my hand at 500mm high and sharp images (as long as the subject itself did not move in these cases). Of course you should select an appropriate aperture and a short exposure time, if possible, when sufficient light is available, to achieve consistently satisfactory results.
Especially important: According to the manual trigger to be about 1 second pressed halfway before you shoot a photo. Only then the image stabilizer works satisfactorily. This I can confirm from my own experience: Failure to do so may lead to strange blurred and shaky results. But you can already see when looking through the viewfinder, from when the image stabilizer starts to act.
