Happily, Myriam included the full source images for the tests, so we don't have to rely on the fragments from the Engadget article, I can pull out comparisons myself for analysis here.
Here's the set-up for the tests:
It looks like Nokia's controversial marketing move, which involved using pro DSLRs to "simulate" low-light shooting, was even less necessary than the smartphone maker may have thought. During our visit to the company's Tampere, Finland research and development complex, we were given access to a comprehensive testing suite, enabling us to shoot with a Lumia 920 prototype and a handful of competing products in a controlled lighting environment. Technicians dimmed the lights and let us snap a static scene with each handset at just 5 lux -- a level on par with what you may expect on a dimly lit city street in the middle of the night. The 920 took the cake, without question, but the iPhone didn't fare too poorly itself, snatching up nearly as much light as the Nokia device. The 808 PureView also performed quite well, but the HTC One X and Samsung Galaxy S III yielded unusable results.
Here's the light-box test scene, to give you an idea of scale:
Then, from left to right, lifted from the raw source images, here are 1:1 fragments of the photos (no flash allowed, devices all handheld but steadied, all set to 8 megapixels) from the Nokia 808 PureView, the Nokia Lumia 920, the HTC One X, the Apple iPhone 5 and the Samsung Galaxy S III:
Quite a dramatic difference between the five smartphone cameras. The Nokia 808 photo is a tiny bit blurred and noisy, but Myriam admits that she hadn't, despite having the 808 in 'Creative' mode, taken any of the settings off defaults. In such a flash-not-allowed test, I'd have upped the ISO figure and expected slightly better results. The Lumia 920's photo is nigh on perfect, despite the very low (5 lux) light levels, showing the benefits of Optical Image Stabilisation (OIS) allowing a shutter time of almost half a second without any blurring of the image.
Of the non-PureView competitors, the HTC One X image was vaguely usable, if way too dark, the Apple iPhone 5 was bright enough but very noisy and blurry, while the Samsung Galaxy S III photo was unusable on every count.
Interesting stuff, but I also noted that Myriam took the same smartphones out around town, including this test shot of the harbour at night:
Taking the shots in the same order and pulling out 1:1 fragments again, so that you can see the differences more clearly, here are photos (from left to right) from the Nokia 808 PureView, the Nokia Lumia 920, the HTC One X, the Apple iPhone 5 and the Samsung Galaxy S III:
Analysis time again. The images from the two PureView devices (albeit with totally different technologies/methodologies) are dramatically more detailed and of higher quality than the competition. Of the two, the Lumia 920's photo (with a full 1/3rd of a second exposure time) was far better exposed and (with the OIS) amazingly detailed. The 808's shot was moody and could be brightened with post processing, but you have to give the win to the Lumia 920 and PureView 'phase 2' here.
The HTC One X image was very noisy, the Apple iPhone 5 image doubly so, with quite appalling artefacts. While, again, the Samsung Galaxy S III camera produced unusably dark and noisy results.
So, other than proving Nokia's continuing mastery of the art of the smartphone camera, does this set of tests settle the PureView 'phase 1' vs 'phase 2' battle? Not really - these shots were purpose-designed for showing off the Lumia 920. I've no doubt that the Lumia 920 will best almost all its competition in the traditional iPhone, Windows Phone and Android worlds under most circumstances, but I'd still take the Nokia 808 PureView over it when considering photos in all light conditions and of all subjects, both static (as here) and moving (i.e. people!) - ultimately the far larger sensor, lossless zoom and quick-freezing Xenon flash would win out for me.
Until we get a review Lumia 920 in, though, I won't be able to test out these other scenarios in detail!
NB. In the interests of disclosure, from the full batch of Engadget raw images, some were in portrait and some landscape, some were also rotated. I've matched like with like here to show almost identical sections as clearly as possible.
Update: the full collection of images is now also available on Flickr.