This Question is not about what aspect ratio should be chosen for the final film, it's rather about how to get the biggest "resolution" capable of the cammera.
When you take a photo with a Modern camera "usually" it's 4/3, I know you can change the aspect ratio, but that's not my point. I assume, that the sensors of DSLR cameras are the same ratio, because they are created for the purpose of creating photos, aren't they?
I guess focal lenght can be taken in account as well.
Now when you shoot Video in 16:9, I assume, that the image is "croped", because you can't change the size and ratio of your sensor.
So the only way, to have that aspect ratio, is to leave it blank or record on the top/bottom of the image (or both) a black bar.
Wouldn't it be smarter, to record with the fullsensor, to get "more" of the image"?
This might sound redicolous, because you'd have a bigge file size and have to put black bars over it in post. But like this you'd have some extra "room", for example someone dips the Microphone or the boom in the picture, you could just crop the clip a bit further down and still be able to use it.
More footage = better to edit, right?
Because you still have the same width of the sensor that you use, you just use all of the avaivable height as well.
Now here is my question: What aspect ratio, should you put your cammera into, to get the highest resolution.