We'll keep these short as there are many combinations to cover.
The Sony Xperia Z5 produced at excellently sharp image (it resolved the blades of grass across the street) and preserved a lot of information as it shot at the highest bitrate, 56Mbps. Colors are a bit pale (like the still camera). A big flaw was the constant focus breathing while video recording - the video is "vibrating," a very annoying effect.
Audio is recorded at 156Kbps/48kHz and sounds very good - ambient sounds are captured in detail and stereo separation is clear. It could use a bit more wind noise reduction though. Since audio capture is identical regardless of resolution, we won't mention it in the other chapters.
The Samsung Galaxy S6 has a wider field of view, though the dynamic range is surprisingly worse than the Sony. This leads to a lot of lost detail in the highlights, also the color processing is unnatural. The focus was rock solid though.
Audio is recorded at a high 256Kbps and is slightly richer than what the Sony captured. Better wind noise reduction helps too.
The Apple iPhone 6s captured video at 50Mbps, the second highest bitrate here (the Galaxy is at 48Mbps). The image could use a sharpening pass, but the great dynamic range allows the phone to capture detail that's almost completely missed by the Galaxy. No autofocus issues either.
The audio is a disappointment though. Apple remains the only company to record mono sound and then only at 80Kbps. The mics are decent - all three of them - with some wind noise getting through, but nothing major. Still, you miss out on directionality of sound, if you close your eyes all sounds seem to come from the same direction.
Winner: Apple iPhone 6s. Come on, Apple, would you switch to stereo sound already? But other than that, the image is detailed without being over-processed and the colors are quite accurate. If your TV has some sharpening applied (and chances are it does), iPhone videos will look great. The dynamic range helps a great deal as well.
Runner-up: Samsung Galaxy S6. We enjoyed the sonic experience, but the weak dynamic range and over-processed video isn't enough to claim the top spot. The wide FoV afforded by the hardware image stabilization is a nice perk though.
The Sony Xperia Z5 could have won this if Sony's vaunted new hybrid autofocus was on point. The image is very sharp (Sony's usual noise reduction smudging notwithstanding), though the colors make the scene look a little bleak.
We'll start off with 1080p at 30fps and then do the 60fps mode. The Apple iPhone 6s again delivers a detailed (if slightly soft) image. Part of that is the narrower field of view, which doesn't stretch the pixel count over too many degrees. Colors and dynamic range are spot on, the audio is a bust, again.
The Samsung Galaxy S6 captures plenty of detail in the image (once you account for the wider FoV), though dynamic range and color rendering are not perfect.
The Sony Xperia Z5 must have been using only a small part of its sensor for 4K, because it has the widest lens here. And it shows in 1080p, it swings from a FoV equal to the iPhone to one wider than the Galaxy. This hurts it on detail, the 2 million or so pixels have to cover much more of the scene. Sony overcompensates by over-sharpening the image, which doesn't look great. Focus hunting issues persist.
When shooting 1080p @ 60fps the Apple iPhone 6s loses a wee bit of sharpness, but almost unnoticeably so.
Doubling the framerate reduced the Samsung Galaxy S6's already short dynamic range and the sharpness dropped. It's good for action-packed scenes, but for calmer videos you would get better image quality at 30fps.
The Sony Xperia Z5 also lost some detail and compensated by dialing the sharpness even higher.
Winner: Apple iPhone 6s. Now, Apple, seriously, about that audio. That aside, the iPhone delivers a quality experience at 1080p - both at 30fps and 60fps.
Runner-up: Samsung Galaxy S6. Bleached out detail is not great and colors are off, but the image looks quite good and covers more of the scene. Going up to 60fps makes some issues more apparent.
The surprisingly wider FoV is great, but the Sony Xperia Z5 goes too wide and the processing makes things worse. 60fps hurts it too and the pain makes for worse processing.
Viewed at 100% the 4K video shot by the Samsung Galaxy S6 looks soft, but almost free of noise. Still, we're not sure it's the best balance.
The noise in Apple iPhone 6s videos is much more noticeable, but the image appears sharper too. Until now the iPhone used sharpening only sparingly, but its tuning for low-light videos allows it to bring out some extra detail compared to the Galaxy.
The Sony Xperia Z5 brings the worst of both worlds - the noise is the strongest and the amount of resolved detail - the lowest. Keep in mind we were shooting at sundown, not even proper night. Sony's inability to deal with low light strikes again.
Winner: Samsung Galaxy S6. The wider FoV naturally puts it at a disadvantage against the iPhone in resolved detail, but keeping the noise under control does a lot to make the videos look good.
Runner-up: Apple iPhone 6s. It had a leg up on sharpness, but the flickering noise isn't becoming of one of the most expensive cameraphones here.
Strongest noise and weakest detail aren't great compliments for the Sony Xperia Z5 camera and you can see that the autofocus is sluggish and uncertain when it comes to videos in the dark.
While the extra sharpening in the daytime 1080p test was a weakness, in the dark it proves to be a strength for the Sony Xperia Z5. The lower resolution allows it to keep the noise in check and with a pinch of sharpness the resulting image actually looks quite good.
The Samsung Galaxy S6 videos are again low on noise, but soft too.
The Apple iPhone 6s couldn't bring the noise down, despite lowering the resolution and the videos appear quite dark too.
Winner: Sony Xperia Z5. The wonky autofocus does it no favors, but the processing here comes together just right. If Sony could find a way to combine 4K mode's daylight performance and 1080p mode's low-light performance, the Z5 could have been a great video camera.
Runner-up: Samsung Galaxy S6. The Galaxy was as surprised to lose its top stop as we were, but while the Xperia actually improved when going from 4K to 1080p, the Galaxy S6 kept the same quality.
The Apple iPhone 6s beat out the Sony in the 4K round, but like the Galaxy it did not benefit from the reduced resolution. Here even its narrower FoV isn't enough to give it an edge in resolved detail.
Both the iPhone and the Xperia rely on electronic image stabilization (EIS), though the Sony has the support of some specialized hardware, which allows it to more accurately correct the camera shake.
The Samsung Galaxy S6 has both electronic and optical stabilization (OIS), though shooting at higher than 1080p disables the digital stabilization. We noticed the Xperia Z5 is smoother at 1080p too and this is Apple's first 4K capable camera, so we picked 1080p instead of 4K to give the phones a chance to do their best at stabilization.
For this test we shot at 1080p resolution with all three phones simultaneously.
Winner: Samsung Galaxy S6. The Galaxy S6 was the only one to dampen lateral movement and overall found the best balance between smoothing out jerkiness and following our intended movements.
Runner-up: Apple iPhone 6s. The iPhone 6s did a great job for a purely digital solution, but it was a little too keen to keep the camera pointing in the same direction, which caused it to lag behind our movements.
The updated stabilization mode of the Sony Xperia Z5 is a big improvement over the Z3+ stabilization, but that's not enough to beat the other two (especially when it comes to lateral movement).