The Nokia 6 has a very compelling HDR (High Dynamic Range) mode. I usually judge the HDR image quality based on how well it is able to bring up the details in overexposed and shadow areas, but at the same time, I look to see whether the image look unnatural or not. I've seen many results that although expose more details in HDR, but the image just look unnatural. Luckily yugatech.com has posted a really nice selection of sample images taken with the Nokia 6. The Nokia 6 camera samples are resized and without EXIF data, but for the HDR I didn't even need one and I could judge it based on the fairly large 1920x1440 pixel resolution image the author posted on the website.
I was really blown away in how good the Nokia 6 handles HDR and how natural the images look. The all idea is to get an image with more unified brightness as seen with our own eyes. Many phone cameras suffer from a low dynamic range and uneven exposure. This leads to the image looking less interesting, lacking of details in bright highlight and dark shadow areas and just less interesting to look at. To make it more enjoyable to look at, it needs to "open up" and let those details, especially in the dark shadow areas come back to life. This Nokia 6 HDR mode does incredibly well.
I didn't look into the technical details how exactly the Nokia 6 does its HDR, but I believe it does that with two or more exposures, because the shadow areas just open up almost completely and you can see many details with even much less noise than before. It like you are looking at a different image, this is how good the HDR mode on the Nokia 6 is. On Yuga Tech website, the author of that post that I was reading say that the HDR combines multiple exposures, so it actually fits my observation analysis perfectly.
It turns image that look flat, dull and boring into vivid, brighter and more interesting photo to look at. It also helps to improve the image quality because usually the dark tones and mid tones have more visible noise, and this is overridden by a brighter color with less or no noise at all. It opens up many details in the shadows that before that weren't even visible, like the color in the leaves of a trea in a photo taken in the afternoon, give clouds more shades and bringing up details in overexposed areas in the sky, which happens a lot when you shoot images with bright clouds in the sky in a very bright day. Even images where the sun is in front of the camera and behind the subject, lighten up the subject and taking it out from the dark. Backlight is usually disastrous for photos because the camera light metering detects strong source of and tells the camera to use a faster shutter speed. The result is that the image then appear darker than it should be, and sometimes the subject looks completely black with the only way to recognize it is through its silhouette. So the Nokia 6 high dynamic range mode does an excellent job there as well.
I highly recommend checking the Nokia 6 camera test photos on yogatech.com. Check out the HDR (High Dynamic Range) images in the middle of the page and see what I mean.