A good way to check the optics on a drone is to take multiple pictures of the same object placed left, center, and right in the frame then compare. This will only give you a basic idea of distortions and varying softness but will show up issues better than trying to subjectively compare the left and right sides of a picture that has significant differences. On the ground you can try using a printed target or object that fills the entire frame. All tests will be pretty rudimentary but will show gross problems in the lens.
