In qandroidcamerasession.cpp the function adjustViewfinderSize selects the viewfinder resolution based on the aspect ratio of the captured image. Since the loop starts from the end of the supported preview resolutions, the final viewfinder size ends to have a higher resolution compared to capture image.

I suggest to match also the area as well as the aspect ratio. AFAK, from QML setting viewfindersize is currently not possible for android camera. Hence in this way, at least the viewfinder resolution will be the same as the capture image resolution (It's unlikely that the viewfinder resolution should be higher than the image resolution).

In the attachment my proposition (line 290-318).