At the HTC One launch, it was clear that HTC had put a lot of effort into the camera assembly of the HTC One, including the use of larger pixels to capture "up to 300%" more light than competing smartphones, and optical image stabilization similar to the Lumia 920. Now I was carrying my Lumia 920 to the event in Sydney, and couldn't resist testing the camera out against the HTC One.
The following shots were taken in similar conditions with both cameras: the Nokia Lumia 920 was using default settings and no flash, and the same for the HTC One except Zoe functionality was also disabled so both phones were taking only still shots. The Lumia 920 is the top photograph from each of the few samples below, while the HTC One is on the bottom.
The Lumia 920 here appears to display more contrast than the HTC One, although the One does display relatively acceptable dynamic range
Again it looks like the Lumia 920 (top) has taken the better photo, as it has more vibrant colors with less grain.
This is a true low-light test of the Lumia 920 vs HTC One, with the shots being taken in a dark environment around 9 PM. The Lumia 920 is not only sharper in the image it produces, but it's also brighter and clearer. The lighting delivered by the HTC One appears closer to the amount of lighting I perceived at the time, but the quality of the shot is not necessarily better.
Of course it should be noted that these tests were conducted in a very short amount of time, and they aren't particularly scientific comparisons. Also, the HTC One could potentially be using pre-release software and the photos I took at the event may not be indicative of what a final product will produce. However, it does give a good idea as to what the "Ultrapixel" camera is capable of versus the trusted "PureView."