For the sake of understanding how the oversampling used on Lumia 1020 is different from that being used on 808 PureView, we reached out to Juha from Nokia. Our question was whether the 5 MP images captured along with 34 MP images from Lumia 1020 uses oversampling like 808 PureView. So, the answer is, yes it does, but there is something called adaptive oversampling which is employed by Lumia 1020. It priorities details in low ISO conditions, which will typically be daylight and good lighting conditions and priorities low noise in high ISO which will typically be night-time and other low-light conditions.
So, it kind of makes sense!! In daytime you capture images with lot of details and inherent noise is itself less, so no need to kill details for reducing noise, but images may be noisier as compared to 808’s images with oversampling. In low-light, oversampling on Lumia 1020 will reduce more noise as in low-light and other high ISO situations, sensor captures lots of noise. and will still provide much more details than any other phone.