To get the most accurate results from the Outfield system, the drone images need to be as high quality as possible. This document explains the two most common issues with image quality and how to avoid them.
Over-exposure happens when the camera exposure setting is set too high and too much light is allowed into the camera. The pixels in the image cannot handle the brightness, and they “saturate” at pure white. This results in loss of information in the image, and it cannot be recovered.
You can check if an image is overexposed by opening the image “histogram” in any photo editing software and looking at the right side of the diagram. If the colour distributions touch the right side of the chart this means some of the pixels are saturated, and the image is at least partially over-exposed.
Example image that is over-exposed
Example image with good exposure
How to Stop Over-Exposure
1. Make sure you use the correct camera settings in Litchi
Follow the Outfield guidance to make sure you have the correct settings in Litchi.
2. Reduce the camera EV setting
For the DJI Mavic 2 Pro, we recommend an EV setting of -0.7 to -1.3 on a cloudy day, and -1.7 to -2.3 on a bright sunny day. On the Mavic 2 Pro, the EV setting is controlled using the right wheel on the back of the controller.
3. Turn on the Litchi over-exposure warning
Litchi has a built-in system to show you parts of the image that are over-exposed. Keep this turned on and use it to decide if you need to reduce the EV setting.
Image blur happens when the camera is not correctly focused on the trees. If images are too blurry, the features on the trees will not be clear and the Outfield detection system will not be able to identify them.
Example blurred image
Example image without blur
1. During the survey, check the Litchi app to make sure the camera is focused
If the camera is not focused, the preview image on the screen will be blurry.
2. Focus the camera on the trees by tapping the screen once
You will only need to do this once near the start of the flight.
3. Make sure your lens is clean
The issue could be as simple as a dirty fingerprint on the lens, make sure to clean the lens with a microfibre cloth before the flight.