FOSS for Android

I will start with Libre Camera, the whole app with data and cache sits at 25mb on my device, a 64gb/4gb one. It's one of the most lightweight things I have used. The greatest feature of Libre Camera, in my opinion, is that you can choose to take photos and videos in it without any exif data -no need for something like Scrambled Exif or any other app. Alongside that you can quickly shift between the "quality" of photos and videos right from the screen, a great feature for when you need to fire up the quality or just need some "potato" quality stuff. And finally, this is perhaps specific to my device, but I had only been able to get "tap to automaticaly adjust iso" (I am not sure what else to call it, but you get the point, right ?) working on it while every other app just returns a dark picture or requires to manualy adjust it all.

With Open Camera, I just like the interface and the fact that you can get reliable pictures and videos quickly. I use it mostly to record videos and it's ability to "lock exposure" has rarely if ever failed me. Also, it offers a truckload of control. I can choose to shoot videos in Webp/Mpeg/HVEC etc, with separate resolutions, and even choose the framerate - again as someone with limited storage that is a blessing.

So, these I think are the greatest quality of these two apps. Finally, these are the only two "good" open source camera app I had seen around in F-Droid. I try to use foss as much as possible, so that's that too.

I hope this was useful in answering your question :)