To test the low-light performance of the phones we took several photos after sundown, and it got progressively darker as we were working. We'll start off in chronological order, with the first photos taken at dusk.
Relying on the built-in OIS to combat camera shake, all three Galaxies were comfortable dropping the shutter speed to as low as necessary, but the wide apertures surely helped, too. A wide aperture lets more light into the sensor, which in turn allows the camera to drop the ISO as low as possible while achieving the same exposure of the scene. Shooting at the lowest possible ISO is always beneficial as the higher the ISO, the more noise there is.
The Galaxy Note5 was the one to retain the finest detail in the center of the dusk photo - you can see the fine lines below the Life sign and in front of the windows. On the other hand, the Note7 and S7 edge did better around the corners, but their processing algorithm and its tendency to over sharpen the image took its toll on the thin lines as there are square shapes were there shouldn't be.
Still, all three phones did an excellent job of shooting at low ISO200, and low shutter speed at 1/25 (1/20 for the Note5), but noise ate into some of the detail on the Note5.
And here are the samples we've used in this test.
We took the final test shot after it was already completely dark. Thanks to the wide aperture and optical image stabilization in all three phones the night photos turned out quite pleasant. The Galaxy Note5 was at a bit of a disadvantage with its f/1.9 vs. f/1.7 in the S7 and Note7 shot at ISO 1000 with 1/8s shutter speed, while the latest generation Galaxies settled at ISO 800 and shutter speed of 1/10s for the same scene.
Nevertheless, the Note5 did great at the center of the image resolving lots of detail. Its noise reduction is low and left visible noise, but it also left lots of fine detail because of that. Its sample is also the brightest one among the three.
On the other hand, the S7 edge and Note7 did great around the whole image, not only in the center. There is fine detail everywhere, and their samples don't have any corner softness. The Note7 due to its improved processing outed a brighter image with more detail in the shadows and more accurate (less warm) colors.
While the Note5 does great around the center of the image, better than the Note7, the latest phablet ticks more right boxes and is thus the better shooter for night scenes. Just don't forget all three Galaxies feature capable manual modes, which can always help you adjust the camera settings instead of settling for the audo tweaks.
We also snapped a few pictures with the flash turned on. All three Galaxies feature a single-LED yet powerful flash, while the processing algorithm compensates for lack of a dual or triple-tone LEDs.
We snapped a photo at 2 feet distance and another one at 4 feet and the wider aperture of the S7 edge and Note7 gave their samples an edge over the Note5.
The two Notes resolve a similar amount of detail, while the S7 edge does better in both scenes. The color rendition of the Galaxy S7 edge is also the best as is the contrast and the white balance.
Winner: Galaxy Note7. The Note 5 low-light photos are great at the center, but very soft around the corners. The S7 edge and the Note7 are sharp from edge to edge, which gives them, an advantage over the Note5. The Note7 has brighter and sharper images than the S7 edge and takes the top spot, though the S7 edge is better when it comes to close range flash photography.