The Nokia Lumia 1020 features an impressive 41 megapixel BSI sensor ZEISS optics with six lenses and “floating lens” Optical Image Stabilization, which allows you to capture sharp, naturally colored and smooth 1080p HD videos, even under challenging lighting conditions.The Lumia 1020 features 4x lossless zoom in 1080p and 6x lossless zoom in 720p. This means that the device can zoom to that level without a drop in resolution. Check out the following 720p video sample which demonstrates the zoom of the Lumia 1020
source - The Nokia Blog