This is a problem for me too - and quite a frustration at the moment as I want to make full sized pictures.
I have found that the image size recorded is (strangely) dependant on the form factor of the tablet/phone controlling the aircraft.
On an iPad - the captured image will be almost 4000 x 3000 (12MP) pixels, and on an iPhone 4000 x 2300 pixels (8.5MP) - so the 4 x 3 capture has 30% more pixels!
In my case the iPhone works well (apart from the cropped image problem), but my iPad is too old to work properly with the Inspire, and now I can't download an iOS app if I was to buy a new iPad.
Are you using an iPS or Android device?
Looks like I'm going to have to dump Apple and go to Android - but I need a tablet with a 4 x 3 format to enable the Inspire to capture a full image. Problem is - which one will work, and does anyone make a 4 x 3 form factor android tablet?