The Apple iPhone 6s and iPhone 6s Plus Review

Video Performance

Now that we’ve discussed still image quality we can start to look at video quality. This is a major highlight for the iPhone 6s’ this year as the main reason for increasing the resolution of the sensor is primarily to enable 4K video recording. Interestingly enough, for the iPhone 6s Apple has also added 1080p120 slow motion video capture along with OIS in video recording for the iPhone 6s Plus. It’s interesting to see this change, as in the past it looked like Apple was solely relying on their EIS mechanisms to smooth out video instead of using OIS. In order to test these changes, we rely on relative testing between two phones to see how both perform in terms of video stability, resolution, and exposure/focus quality.

For 1080p30 video, Apple continues to use H.264 high profile encoding at around 17 Mbps bit rate, which is carried over from the iPhone 6. AAC at about 84 Kbps in a single channel is also carried over from the iPhone 6. It’s likely that mono audio is used because the microphone setup doesn’t really support stereo audio, but in future iterations it would definitely be interesting to see stereo audio recording. For all other modes, encoder settings appear to be constant with variations in bit rate based upon frame rate and resolution.

When comparing the iPhone 6s and iPhone 6 for general image stabilization quality it feels like they’re both pretty much identical. If you’re not careful about holding the phone relatively still EIS is going to feel a bit limiting. However, Apple’s EIS is quite good compared to something like the Galaxy Note 5’s video OIS due to its rather unnatural dampening effect, in which there are pockets of local stability punctuated by no stabilization at all. It’s also interesting to see how the iPhone 6s and 6s Plus appear to still have an edge over the Note 5 when it comes to continuous auto focus as in this scene the Note 5 takes some time to recognize that the subject of the video is out of focus and some contrast AF bracketing is used to verify the correct focus point. By comparison, the iPhone 6s appears to snap to the correct focus point almost instantly.

The iPhone 6s Plus is clearly the best out of these four phones though as it manages to combine the rather natural EIS of the iPhone 6s with properly implemented OIS. The algorithm for using OIS appears to be intelligent enough that overall image stability is prioritized over locally minimizing camera shake, which shows as footsteps in the video are properly dampened along with hand shake, but the major deviations are left alone. This looks much more stable when compared to the Note 5 because the Note 5 does appear to cancel out major movements in the video, but as soon as the OIS runs out of travel there is a strong correction that causes an unnatural jerking effect.

Here, the iPhone 6s compares pretty favorably with the best video cameras in the Android space. Relative to the Galaxy Note 5, the iPhone 6s has better color reproduction and dynamic range. This is especially evident when looking at shadows in the scene. Although this scene was shot towards the end of the day, the Note 5 makes the trees look much more yellow than they should be for accurate color. Due to the wider field of view, the Note 5 appears to have less detail as well, but zooming in should resolve the issue.

However, the iPhone 6s does end up worse than the Note 5 in some ways for this video. One obvious issue here is that the lack of OIS means that high frequency motion is especially hard to compensate for, which is more obvious in this test where I’m basically standing still instead of walking around trying to push the OIS beyond its travel limits. The Note 5 also has noticeably better audio quality due to the use of stereo recording.

The iPhone 6s Plus does go a long way to remedy these competitive deficits though, as the addition of OIS means that hand shake is pretty much eliminated in these relatively still videos. Apple’s use of a rather tight crop by default also means that the noticeable edge distortions induced by OIS are hard to notice, but given that a lot of people seem to prioritize field of view over general optical quality this may be considered a negative.

Weirdly enough, when comparing the iPhone 6s to the iPhone 6 there are some very real improvements to detail in 1080p video. It’s possible that we’re looking at the result of the 12MP sensor providing more pixels for oversampling here, as the field of view for both is pretty much identical. Overall image stability is basically the same here, which leads me to believe that cinematic video stabilization/EIS introduced with the iPhone 6 is basically unchanged when compared to the iPhone 6s. Color reproduction basically looks the same as well.  Recorded audio is noticeably different in profile to make things less tinny, which is a nice improvement but not really enough to make audio recording in these situations better than the Note 5.

Meanwhile for 1080p60, it feels like the gap is even wider when it comes to detail as the iPhone 6s and 6s Plus has pretty much equivalent detail to the 1080p30 mode but with a higher frame rate. Color reproduction takes a noticeable dive as well towards overexposure and an even stronger yellow tint which is kind of surprising to see. The iPhone 6s continues to maintain a noticeable lead in quality over the iPhone 6 as well.

In 4K30, once again we see a surprising gap in fine detail and shadows. Color rendering of the trees also continues to be strongly saturated with yellow, which is a bit unrealistic for this scene. In stark contrast with most of the phones I’ve tested, 4K video on the iPhone 6s still has cinematic video stabilization active. There’s also no actual recording limit, which I tested by recording 4K video for roughly half an hour until it was evident that the phone wasn’t going to stop recording. When comparing to the iPhone 6’s 1080p30 output it’s evident that there isn’t really any compromise other than additional storage use.

In 120 FPS slow motion the iPhone 6s’s are basically as good as it gets. Due to the resolution advantage no other OEM is really challenging Apple here. The 1080p120 video isn’t quite as high in detail as 1080p30 or 1080p60, but even a high quality 720p video isn’t really comparable.

Meanwhile in 240 FPS detail is comparable when comparing the iPhone 6s to the iPhone 6, but the iPhone 6s does appear to be slightly improved. I suspect we’re mostly looking at limits of the resolution here rather than encode or camera-level limitations.

Overall, the iPhone 6s and 6s Plus are both some of the best phones on the market for video capture. The iPhone 6s Plus manages to lead over the iPhone 6s by virtue of its OIS, but even without it the iPhone 6s is clearly pulling ahead of others when it comes to slow motion and 4K video capture. Looking at both video and still image performance together, the iPhone 6s Plus arguably has the best camera in an iOS or Android smartphone today. It isn’t necessarily the best at sheer detail for still images, but the camera doesn’t do anything wrong. The iPhone 6s Plus leads in overall low light photo quality, camera user experience, and overall video quality. The iPhone 6s is decidedly a few steps behind due to its lack of OIS, so as a result I would rank it around the iPhone 6 and Galaxy S6.