Both of the LG G6 rear cameras, the wide-angle and the normal one, utilize the Sony IMX258 1/3.06" 13MP Exmor RS CMOS sensor. This is the same sensor found in the Oppo A57, Asus ZenFone Pegasus 3s and BLUE Vivo 6 among others. Given a f/2.2 aperture, the Sony IMX258 doesn't perform well in low light, like in the OPPO A57. However, the LG G6 has actually two cameras, one with a 71-angle field of view with an f/1.8 aperture lens and a second one with 125-angle field of view, with a f/2.4 aperture lens.
I don't expect the 125-angle lens to perform any better if not worse than the OPPO A57 one, it's 1/3-stop slower after all. I'm more interested to see how the first sensor performs, the one with the F1.8 lens. Juts so you know, the Sony IMX258 sensor uses Sony's advanced Stacked BSI CMOS technology, so it was designed to perform well in low-light, at least relative to equivalent sized sensors with regular BSI technology.
Luckily for all of us, there are plenty sample images already available on the web shortly after the LG G6 announcement. I could already tell by viewing some images taken with the different sensors that the wider angle one performs more poorly than the other sensor that features a faster lens, but I had to find full resolution images with the EXIF data, so I can better analyze the image quality and come to a more accurate and objective conclusion.
i found two G6 sample images shot by phone arena, showing the same exact scene, one shot with the f/1.8 camera and one with the f/2.4 camera. The F1.8 one shot in ISO50 1/609s shutter speed and the F2.4 one shot in ISO50 1/361s shutter speed. First of all, the 125-angle camera has severe distortions. It definitely capture a much wider field of view, but with strong barrel distortion. The distorted area is also very soft. I know it's a Leica lens, but the lens definitely performs very poorly in the corners. The center of the frame however is sharp.
The Primary camera with the smaller FOV produces a sharper image and it's very sharp at the center. It's kind of weird though, because I saw sample images with some weird noise patterns ant jaggies that might suggest a poor image processing or over-sharpening for JPEGs by default, but in some images I couldn't notice it.
I have to admit that I wasn't impressed with the image quality considering this is LG's flagship smartphone and it was supposed to showcase a very high image quality and low-light performance. I've seen some low-light sample images taken with the f/1.8 camera and wasn't impressed at all.
I think that the major problem is that Sony IMX258 sensor and its tiny pixels. I've seen that poor performance on other smartphones, and it's not just that it's going to do any magic on the LG G6. The f/1.8 help a bit of course, but the LG G6 just can't match the performance of the leading flagship models like the Google Pixel, Samsung Galaxy S7 and iPhone 7 Plus. How can it even compete against the upcoming Samsung Galaxy S8. I just hope that Samsung didn't opt to go with that sensor. It's just a nail in the coffin for LG, at least when it come to phone's camera capability.
I also didn't like how it handles front light, the dynamic range is low and even the colors seems a bit off. I just couldn't point out the exact problem, but looking at duzen of images, I just didn't like what I've seen. The 125-angle camera is just not suitable for low-light due to its f/2.4 aperture lens. It will force the camera to shoot at very high ISO which will lead to very noisy images.
I don't know what to say. I had high expectations from the G6. In some ways I really wanted to convince myself that maybe the photographer just did a bad job in taking a good image and it doesn't represent what the LG G6 cameras are capable of. However, I did spend time inspecting the EXIF data and went over quite a lot of sample images. So this lead me up to a conclusion that the LG G6 rear cameras' performance is quite poor, especially in low-light.
Regarding the video quality. I found it to be very good. Of course it's moving images, so I can't really analyze the video the same way I analyze sample images. I cans ay that the color reproduction looks very good, I love the vivid colors and the video, at least that taken by GSMArena, look really sharp.
Here is the sample video taken by GSMArena with the LG G6 at 4K resolution.
I am interested to hear what you think about the LG G6 image quality from what you've seen so far. Thanks. Please keep in mind that those sample images that I examined were most probably taken with a pre-production model not the retail unit ones. The results might be different from the final product. Still, I am little optimistic that there will be a significant change.