It's hard to take video modes on phones seriously. Cameras that take professional-quality video cost thousands, and regular consumer cameras don't tend to match the video quality even if the specs seem similar. If you've used the video modes on point-and-shoot compact cameras, you're going to be expecting the worst.
So the iPhone 6S video specs sound wildly ambitious – good-quality 4K video on a mobile phone? Really? Even more outlandish is the Slo-mo mode, which can – allegedly – shoot standard 720p HD video at an amazing 240fps. Played back at 30fps, that gives you an 8x reduction in speed.
The 4K is fantastic
One of the reasons for getting a video expert like Dan on board is that he knows how to use a camera so that you're only revealing any faults in the camera's performance, not in the operator's technique.
And Dan had high praise for both the detail rendition – we watched 4K video played back at 100% magnification on a computer screen – and for the way it handled movement. This clip (above) really shows the level of detail the 6S can capture, and the lack of compression artefacts and texture smoothing in the stone fountain.
I am genuinely impressed with the video quality, though you can't control the shutter speed so video shot in bright light at fast shutter speeds has a less natural appearance – this is where you need a DSLR or a CSC.
Cheap consumer cameras often blur fine detail with heavy inter-frame compression, but the iPhone's 4K footage is really clean, sharp and stutter free. If you do see stuttering, that's more likely to be caused by what you're playing it on – relatively few computers have the graphics power needed to play back 4K video smoothly.
Here's another example of the iPhone 6S's 4K video quality. The autofocus can't quite keep up with the spider as the wind blows the web to and fro – that would be a lot to ask of any camera – but when it snaps into focus the level of detail is very high. The second video, directly below is a 1080 full HD crop from the 4K version. Remember this is now just one-quarter of the 4K image area captured.
The iPhone doesn't always get it right. In the video of the swans, above, it starts off well, but the sudden switch to a darker background mid-way through makes it over-expose the swans badly. The solution, however, would be to set the AE/AF Lock before filming.
In this clip you can see the effect of the lack of shutter speed control. The shutter speed is quite high, even in these shady conditions, which makes the movement of the dogs look slightly less smooth than it should.
You might not see the need for 4K video now, but in the future when 4K devices are everywhere, you may be glad you shot it. But if you do plan on shooting 4K footage, don't even think about getting a 16Gb iPhone 6S – 4K video takes up almost three times the space of 1080, and you'll fill up the phone's memory in minutes.
It's true that even the screen on an iPhone 6S Plus is only 1080 resolution, but don't forget you can pinch to zoom even during video playback, and this is where the sheer level of detail in the 4K footage becomes apparent.
It is a bit annoying that you have to go into the iPhone Settings just to swap from 4K to 1080 video.
If the 4K video is impressive, the Slo-mo mode is better still. 240fps footage played back at 30fps is amazingly smooth and detailed, and the iPhone has a neat playback trick, where the first couple of seconds are played at normal speed and then it shifts down into slo-mo mode. For the final couple of seconds it shifts back up to normal speed again. This gives a really nice effect, like a properly edited movie rather than a straight slow-motion clip.
Interestingly, when you play these Slo-mo movies back on a computer, you don't get this speed change – the movie is in slow motion throughout. The speed changes are applied by the iPhone and not baked into the video.
In fact, you can open a Slo-mo movie, tap the Edit button and change the points at which the playback speed changes. You can also trim the ends of Slo-mo movies (and regular movies) and export trimmed movies as new video clips.
The Slo-Mo version of our fountain video is captured at a resolution of 1280 x 720, which is really impressive given the frame rate – but you can see a lot more texture smoothing in the stonework of the fountain, indicating higher levels of compression.
Handily, shooting in slow motion also helps disguise camera shake from shooting handheld – you can afford to be more experimental with your filming.
Here's one unexpected thing – the Slo-mo mode also records audio. In our slo-mo shot of a fountain, you can hear the water trickling. Things get weird with human speech, which slows into a kind of menacing subterranean growl, but it adds to the fun and it's way better than having no sound at all.
In lower light levels, Slo-mo movies can lose a little crispness, but the 6S should get due credit for being able to shoot 720 movies at 240fps in the first place.
The Time-lapse mode is fun, but fairly limited. The idea is that you capture a series of still images in real time and the camera turns them into a movie played back at a higher speed. It works fine – a stylised stopwatch spins round ticking off markings around the dial (each one is another frame) until you tap the button to stop. You then see a speeded-up movie made out of the individual frames.
You could use it handheld for a kind of first-person movie, or you could use a phone clamp and a tripod to record a sunset or a busy city street at night, say.
The Time-lapse mode is all right, but you can't change the speed. I'd just use Instagram's free Hyperlapse app, which lets you change the speed after you've shot the movie.
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