It's pretty safe to say that PureView is one of the best cameras ever put in a phone. What is PureView, you ask? It's a 41 megapixel camera
stuffed into the body of a phone. And yes, stuffed it is, as it's large enough to make a sizable bulge on the back of today's thin phones. You can read the full details on it from Nokia here
, but I'll give you the summary of how the technology works.
It's similar to something called Full Scene Anti-Aliasing, which you may have noticed in a game's graphical settings as FSAA. In games, you render the screen at several times the resolution of the screen itself, then downscale to make it fit in the given resolution. This process helps to reduce sharp edges and gives a more natural look, but it's computationally expensive to render at such large sizes, and vastly more taxing as the size multiplier is raised. In the case of PureView, you start with a 41 MP camera, then downscale the image eight times, rendering to a 5 MP image, meaning eight pixels on the actual sensor will be only one pixel in the finished image. The camera is capable of having this anti-aliasing reduced or removed as well to increase the resolution of the image if desired.
Of course, the sensor is only one part of what makes a camera good. The sensor needs good optics in front of it and good software behind it to gather the light and process it into something beautiful. The software is especially important when it comes to video, which is certainly a difficult feat with dealing with a 41 MP camera. Nokia is certainly skilled with both hardware and software, and the optics in the Lumia 900 were something to set it apart back during CES. At the moment PureView is only available on Symbian as the technology is actually five years old and only now coming to fruition, but as you may notice from the second article I linked earlier, Damian Dinning states that "Aspects of this technology will be used in future products yes." WPCentral states that it will be coming to Windows Phone specifically.
This isn't the first time new hardware has been tested on Symbian first; after all the Lumia 800 is extremely similar to the Nokia N9. It makes sense for Nokia to start development on the platform they created, then as the kinks are worked out move it to the platform they continue to redefine to higher standards with every bit of news. Maybe we'll get lucky and net some huge cameras before WP8 even comes out?