There are several reasons why images captured in flight might not be as sharp as expected. These reasons include slow shutter speeds, engine exhaust passing through field of view, and even the corner sharpness properties of wider lenses. If yo ubeleive the focus of the lens might be off, the best place to start is with a ground test. When performing a ground test you will need a few things:
- A power supply for the camera (this could be the wall plug or an iX Controller)
- A USB cable to tether to a computer or controller.
- A location with objects sufficiently far away.
Place the camera on a stable surface - or mount to a tripod if possible. Do not hand hold the camera during this test!
Use an appropriately fast shutter speed to prevent motion blur in the scene. Aim for 1/1000s or faster if possible. Slower is OK as long as the camera is not moving at all.
Use Aperture F/5.6 and the lowest ISO that will get a good exposure.
If you are in a hot areas with a lot of heat distortion, the test should be performed early or late in the day.
Take several images. The goal is to have far away objects visible at the edges of the frame that should be in focus at infinity. See the examples below: