The iPhone 5S has an all new camera compared to the previous generation iPhone 5. This new camera has a sensor that is 15% larger than the iPhone 5 but stays at the 8-megapixel count.
Apple made it clear that the iPhone 5S has bigger sensor nodes, the nodes are at the size of 1.5 microns. The Nokia Lumia 1020 has 1.1 microns. Apparently this is supposed to help the camera catch better pictures and especially have better dynamic range.
The camera now uses an f/2.2 aperture which should offer brighter pictures compared to the f/2.4 in the iPhone 5.
The sample pictures from the device are pretty amazing for a camera on a smartphone. But the real test will come when it compares to the likes of the Nokia Lumia 1020 and the Xperia Z1.