Looking at the source code, they're using the newer Camera2 API. I have no expertise in implementing said API, and a quick comparison between Signal's code and that of Open Camera suggests the Signal developers don't have a whole lot more.
It also has some questionable decisions in it like cropping to close to the screen's aspect ratio rather than using the native aspect ratio of the sensor. I never want that behavior.
It also has some questionable decisions in it like cropping to close to the screen's aspect ratio rather than using the native aspect ratio of the sensor. I never want that behavior.