Having recently looked in detail at the Lumia 1520's PureView camera against the flagship 1020 for stills, it's time to pitch the two devices for video capture. And with interesting results, as you'll see in the side by side video comparison below.

Long time AAWP readers may remember my video head to head of the Lumia 1020 with the previous phone world camera/camcorder champion, the Nokia 808 PureView - in my comparison, it was self-evident that while the 1020's raw performance was slightly below that of the larger 808, the presence of OIS (Optical Image Stabilisation) made a huge difference when experimenting with the lossless PureView zoom.

It therefore surprised me to discover, during the course of the test below, that the 1020's OIS utterly pales compared to the effectiveness of the (admittedly) smaller OIS mechanism in the Lumia 1520. See below for comments on the various scenes in the video.

In terms of specifications, the Lumia 1520 ('phablet')'s camera can zoom in losslessly into its underlying 20MP sensor, giving a zoom factor of 3x for 1080p capture (as shot below, c.f. 4x on the Lumia 1020) and 4x for 720 capture (c.f. 6x on the Lumia 1020). You can see 3x vs 4x clearly in the video.

As a sidenote to this test, note that the Nokia 808 achieved its spectacular video quality by using a dedicated hardware image processor to oversample from the 41MP sensor down to 1080p in real time, i.e. the 'pure' pixels applied just as much to video as to still images. The Lumia 1020 and 1520 rely on their main processor and GPU for video capture/zooming and there's no discernable real time oversampling. Of course, set against this is extra purity and stability coming from the use of OIS, plus when using the PureView zoom you end up down at 1:1 on the sensor anyway and thus there wouldn't be anything to oversample from. Pros and cons to both approaches, of course. Again, see the 808 vs 1020 piece for an example of output.

On with the test then, with footage taken in overcast conditions and in weak winter sun here in the UK. As usual with such videos, maximise the playback window and 'up' the quality if your bandwidth can stand it. 

Also, note that the footage has been rendered out in iMovie (enabling the side by side effect), plus there's also YouTube's own resampling, so you're not seeing original footage quality (see below for this) in this embed. It'll give you an idea, though:

Sections from the sample video, things to note(!):

1. Graveyard. Contrast seems artificially high in the 1520 footage. Just as with still images, curiously. Obviously something here for the boffins at Nokia to tweak in the firmware.
2. Churchyard. Again, higher contrast - though this does seem attractive at first, it gets wearing once you realise that it's artificial. The zoom test shows the difference between 4x and 3x lossless PureView zoom.
3. Churchyard walking test. The OIS in the Lumia 1520 camera is much more effective than that in the 1020 - this is almost certainly the difference between the MEMS-based OIS in the smaller camera versus the ball bearing mounting approach in the larger 1020 camera unit. 
4. Flooding and zoom. Again the 1020's zoom is obviously more effective here, plus the footage more natural, though again the 1520's better OIS keeps the scene more stable.
5. Traffic and floods. More of the same. Stable footage from the Lumia 1520 impressing again.
6. Night time. Both devices had problems focussing, not surprisingly, so each was set to infinite focus - a really useful feature in Nokia Camera. The scene to my eyes was a lot lighter than it appears in the video frames, interestingly. Other non-Windows Phone cameras produced a significantly lighter video image, albeit with more digital noise. An interesting choice made by the Nokia team here, especially given that still images in low light appear much lighter than they do to the naked eye.

You can download a sample of original Lumia 1520 1080p MP4 here (i.e. without iMovie and YouTube re-encoding getting in the way).

Audio capture on the 1520 was of very high quality, though I didn't test at 'rock gig' volume levels - I'd expect the same excellent tolerance as the 1020 here, with Nokia's Rich Recording system in place. Of note on the 1520 is that there are no less than four HAAC microphones, one at the end of each 'face' of the phone, producing a better stereo image generally and yielding a 'directional stereo' option in the Nokia Camera settings, in this case prioritising the front-mounted mike pair. We saw a good demonstration of this in action in this Nokia-shot music video. 

Verdict

As you tell above, I was alternately impressed and disappointed by the video from the Lumia 1520 - the OIS works superbly and the PureView zoom works as advertised - if this physical camera unit is to make it into multiple 2014 Windows Phones then end users are going to be delighted, especially when allied to the wonderfully large and clear screen outdoors (on the 1520, at least).

However, there's clearly work left to be done in terms of sensor processing when capturing video, and the 1520 footage above all felt harsh, artificial and with too much artificial contrast. This is exactly the sort of thing which can be tweaked in a firmware update, so I'm not too worried - again, it should be noted that the flagship 1020 has already received multiple updates.

PS. See also Rafe's comprehensive review of the Lumia 1520's hardware and place in the market.