All consumer drones available today already have a built-in camera including a corresponding camera mount. Most cameras are optimised for video recording, but photos can also be taken. The live image from the camera is usually transmitted to the smartphone/tablet, which is also used for control. These components are adapted to the drone and optimised in size; in most cases, no changes can be made. Therefore, the following information is aimed at pilots who are thinking about building a drone themselves or who have a multicopter on which adjustments/changes to the equipment can be made.
Choosing suitable camera equipment is always a compromise between the camera's performance and its weight. First, check the maximum load the multicopter can carry. Note that the weight of a lens and the weight of a camera mount or gimbal may have to be added to the weight of the camera. In addition, the multicopter should still have power reserves for a safe flight despite the additional weight and should not be working at the load limit.
When deciding on a camera, you should pay attention to the following points:
- Distortion-free wide-angle lens: Current action cams have enormous advantages in terms of weight and resolution, but usually the extreme wide-angles of their lenses lead to strong distortions at the edge of the image, which among other things leads to a curved horizon in aerial images. More suitable are current full-frame cameras that allow a change of lenses.
- Remote release: To be able to release the camera at the right moment, the camera must have a remote release function. Many cameras have special plugs that can be used to trigger the camera by means of an electrical signal. Other cameras can be triggered via a coded infrared signal (similar to TV remote controls). It is important to find out how this remote triggering can in turn be controlled via a radio remote control.
An inexpensive alternative to this is to set the camera to continuous shooting mode so that it takes a picture by itself every few seconds. After the photo flight, this leads to a lot of waste in the shots taken, but this is no longer an issue in the age of digital media.
- Video output: The favoured camera should provide the current live image of the camera at a video output. There it can be tapped and transmitted to the pilot via video radio link. With some cameras, the live view is automatically deactivated after an adjustable time in order to save battery power. It should be possible to deactivate this.
The correct alignment of the camera cannot be achieved by manoeuvring the multicopter alone. The camera therefore needs a suitable suspension that can be influenced in at least one plane (tilt angle) by the pilot via radio remote control. Currently there are 2 types of camera suspensions:
- brushless gimbals: State-of-the-art gimbals are controlled by brushless motors. Since these motors are very fast and powerful, the movements are smooth and jerk-free. These gimbals also have their own control component that ensures that a set camera orientation is maintained even when the multicopter makes compensating movements. This makes brushless gimbals particularly suitable for filming.
- Gimbals in which the rotations are taken over by servo motors are much cheaper and lighter than brushless gimbals. However, the rotations are much more jerky due to the servo motors. But as long as you are only taking photos, this is almost irrelevant.
In order for the pilot of the multicopter to be able to check the current image section of the camera, the live image output by the camera should be sent to the ground via video radio link. For this purpose, a corresponding video transmitter is installed on the multicopter and the live image is fed into this video transmitter. A video receiver on the ground receives the video signal and forwards it to a monitor or video glasses.
Since most digital radio remote controls today transmit on the 2.4GHz band, it makes sense to send the video signal via a radio link in the 5.8GHz band. In Germany, a maximum transmission power of 25mW is permitted in the 5.8GHz band. This limit must be observed, especially with video transmitters imported from Asia, as these often have a significantly higher transmission power.