Apple has upped its selfie game for the second generation in a row - from the measly 1.2MP excuse for a front camera on the iPhone 6, through the 5MP shooter on the 6s and now 7MP on the iPhone 7. The lens aperture has stayed the same throughout these iterations at f/2.2, making it the darkest of the bunch, and with a 32mm-equiv. focal length it can also fit the fewest people in the frame at an arm's length.
The Xperia XZ and the Galaxy S7 have a substantially wider field of view thanks to 22mm-equivalent lenses, while the G5 is in the middle with what math insists is a 28mm-equiv. focal length. The S7 sports the widest front cam aperture - at f/1.7 it matches the one on the phone's primary shooter. The G5 and XZ have a standard-issue f/2.0 aperture.
The Galaxy S7, however, has the fewest pixels to work with - just 5MP, while the Xperia XZ boasts a 13MP sensor. The G5 again occupies the middle ground with 8MP.
A few peculiarities on the interface must be noted. While the shooting modes on the iPhone are changed with side swipes, switching between cameras requires a tap - not very user friendly. A downward works on both the G5 and XZ, which is great, given the distant location of the button that does the same on the G5 and the XZ. The Note7 introduced a similar feature, which may eventually trickle down to the S7, but as it is, at least the front/rear toggle is well within reach.
Additionally, the G5's resolution selector is borrowed from the rear camera, which has a 16:9 sensor, as opposed to the front shooter's 4:3 imager. Not knowing that, you may be fooled into thinking that opting for 16:9 would give you the full 8MP - it won't. We can think of at least a few reviewers that have had to reshoot their photo samples because of this. We'd hate to be them.
On to image quality. In good light, if we had to name a winner (which, we sort of have to do), that would be the Xperia XZ. The wide-angle lens offers great coverage and the 13MP sensor has what it takes to resolve the data in there, but that's hardly a surprise. Colors are generally accurate, and dynamic range is pretty good. Also, this being the only selfie camera with autofocus among our cameraphones, it's got the benefit of allowing you to shoot at various distances other than an arm's length.
The LG G5 comes next, and is close to the Xperia (without matching it) in per-pixel detail - lower-res sensor, but also narrower field of view.
The iPhone 7's images have pleasing colors, but are softer overall. It's not its biggest problem though - the narrow FOV will make group selfies a real challenge. Not to mention that none of our selfies at an arm's length came out tack sharp - it turned out that the focus was tuned at a closer distance and the camera really showed what it's capable of when we moved close. No doubts about it, this one was obviously meant to be a single person selfie cam.
The Galaxy S7 can only do so much with its 5MP - high-frequency detail like hair is inevitably lost, but it will do for social media.
Daylight selfie photos winner: Xperia XZ. Very detailed wide-angle selfie camera with good exposure and dynamic range, has autofocus, too.
When light levels drop, the balance of selfie power shifts and the Xperia no longer remains the king of the hill. Sony's smartphone chooses to jack up the ISO (800 in this next shot), which forces it to deal with noise and the noise reduction does away with fine detail. Not to mention that auto focus on the front camera refuses to focus properly once the light gets dim just like the main camera.
The iPhone 7 suffers from noise as well, but then it also desaturates the colors.
It's a close call between the G5 and the S7 in terms of resolved detail, but we'd have to give this one to the S7 for better developing the hair and shadows overall. However, the G5 is better at keeping the the skin tones looking more natural.
Low light selfie photos winner: Tie between the LG G5 and Galaxy S7. The Galaxy S7 manages to retain the most detail, but the G5 does a better job with skin tones.