One of the best things I love about the OnePlus 3T main camera is its HQ mode. In this mode the capable of capturing high ISO images with a fine grained noise patterns. A noise patterns that looks like little sand particles that cover the photo. In this mode, the camera can capture images with better fine details because the fine details aren't destroyed by strong NR reduction algorithm.
The main benefit for me is that image noise of this type is can more effectively be removed/reduced using noise reduction software. I don't mean mobile phone apps, but noise reduction software that you run on your computer. The reason why I prefer a NR software is because of the more powerful and sophisticated algorithms that are used their because of the powerful processor found in PC computers compared to mobile phone CPUs and GPUs. Even several RAW image processing software allows you to choose between a slow processing and faster processing, so even a very powerful PC with Intel i7 processor can take time to process a high resolution image.
My favorite noise reduction software is Noise Ninja, developed by PictureCode. I've used their product before when it was a standalone product, but now Noise Ninja 4 is integrated into a n all-in-one RAW converter software.
I've searched the web for a OnePlus 3T high ISO sample image that has a lot of noise and I wanted to see how good Noise Ninja will process it. This is the original image on imgur.com (image credit: hyuratzu user from xda-developers.com) If you magnify it to 100% size you can see that it has a lot of finely grained noise patterns.
Now, I processed the image using Noise Ninja and you can clearly see how well the image looks.
I could tweak the noise reduction to my liking and maybe add extra sharpness at the cost of more noise. It depends on the specific image that you want to process. Of course the reason I've edited it is to show you how good noise reduction software can process an image with that noise patterns. I have a lot of experience in processing many images with different type of noise patterns, but this one just works the best because the algorithm is looking at neighbor pixels to determine what is noise and what is not. If there wasn't an area of the sky there, I would probably put a little more sharpness to the image.
The settings I used with Noise Ninja 4: For Luminance noise reduction: Smoothing 100%,Residual noise and detail 29, Color noise reduction: 73 strength and 0 Defringe.
Keep in mind that the image above shows a 100% crop of the original image. When resized you won't even notice any noise and it would appear very clean and sharp. There is of course lose in very fine details, but if I brought an image with smudgy noise patterns, it would have looked much worse. The results are great as you can see.
This is why the OnePlus 3T HQ mode, as well as RAW shooting mode, both produce image noise patterns that are easy to remove using advanced noise reduction software. There might be some good noise reduction apps for Android that work well, I just didn't tried them out because I enjoy editing images on my home computer and not on a mobile phone screen.
I highly recommend downloading the free trial license of Photo Ninja and try it out. Who knows, you might discover how amazing it is editing your photos on your home computer if you haven't tried it before.
This is certainly an advantage that this OnePlus 3T has that can sometimes be overlooked by enthusiast photographers and I though it's important to bring it up.