Nobody really wins in this particular section, as each smartphone comes with its own pros and cons, none of which significantly one-ups the other.
The iPhone 6s Plus really gets one thing right in low light: Its optical image stabilization (OIS) is excellent.
In dark environments, your camera needs to lengthen the shutter speed to capture more light, but that increases the risk that your shot will be ruined by your hands moving, resulting in blurry photos. Even the smallest of movements can cause motion blur.
The iPhone 6s Plus’ OIS manages to keep shutter speeds low while remaining steady, which also has the advantage of keeping the ISO, and thus image noise, low. The two shots below are an example of how the iPhone 6s Plus’ OIS helped me get a steady shot in low light, while the S7 Edge’s shot turned out blurry. This is despite the iPhone 6s Plus shooting at an even slower shutter speed than the S7 Edge.
But the iPhone 6s Plus also takes chances, way too many chances. For one, low shutter speeds are fine for still subjects, but if you’re shooting people at 1/8th of a second, for example, any slight movement on their part will result in blurriness. The iPhone 6s Plus also doesn’t warn you to keep your hands steady when it’s shooting at such low shutter speeds, which is downright irresponsible.
The iPhone 6s Plus also tends to produce flatter colors in low light, which is a big strike against it. See the extreme test shots below in near dark; I’m completely dull in the iPhone 6s Plus’ shot, while the S7 Edge manages to retain the color of my skin and shirt. The S7 Edge also manages to collect more light, possibly due to its faster lens.
This doesn’t just happen in extreme low light, but in moderate low light as well. Notice how the colors in the iPhone 6s Plus’ images are duller compared to the S7 Edge’s.
But the iPhone 6s Plus’ biggest weakness against the Samsung Galaxy S7 Edge though, is how its AF is usually slower than the S7 Edge’s in low light, and much less accurate.
Unlike the iPhone 6s Plus, the S7 Edge can lock onto the correct subject quickly in low light — much more quickly than any smartphone camera I’ve seen to date.
As seen above, the S7 Edge’s images retain more color in low light than the iPhone 6s Plus’, which is a key highlight. I also appreciate how Samsung has toned down its (usually) harsh noise reduction on the S7 Edge, allowing more image noise, but also more image detail, to show through than on the iPhone 6s Plus. See the Note 5’s image to see how its heavy noise reduction has reduced details to indistinct smudges.
However, the S7 Edge’s OIS is not as good as the iPhone 6s Plus’, and I got more blurry shots in low light due to camera shake. The S7 Edge does warn you to keep your hands steady (in Auto, not Pro mode), but sometimes that’s just not easy to do. In the samples below, I shot the iPhone 6s Plus at a seriously low shutter speed of 1/17th sec, and it turned out sharp. The same shot with the S7 Edge at 1/10th sec, and it turned out blurry. It didn’t happen in just this one instance, but consistently across my low light shooting experience with the S7 Edge.
So, who wins, who loses? The Samsung Galaxy S7 Edge’s AF is obviously better than the iPhone 6s Plus’ in low light, and I prefer the punchier colors and fuller details from its images, although they do come with more image noise. However, the iPhone 6s Plus will help you nail sharper images in low light than the S7 Edge, with its excellent OIS, which is no small feat either.