The light sensor and calibration panels are both tools for calibration that yield more or less accuracy depending on the situation. We can use different methods depending on the weather conditions and use case of the data. While our DLS does a great job of estimating changing light conditions, it's not a perfect measurement due to various factors, including movement of the drone.
When the light is constant, the errors in the DLS measurement of the light will be more dramatic. Because instead of being random, the error will come from the fact that the drone is pointing the light sensor in one direction and then the other for long straight runs which can result in biased data along these runs. This difference doesn't usually show up, but in cases where the target area is especially uniform, it can be noticeable.
With that in mind:
In the case of a clear, sunny day, we recommend using only the calibration panels. Light sensor data will not be as effective and so should generally not be used in this case.
Light sensor data is most effective in overcast, completely cloudy conditions. In this case, we would recommend using both light sensor and panel data for calibration.