Multirotors and Cameras

Once pilots get familiar with flying their multirotor aircraft, they look for interesting new things to do with them. Many times, they will carry some type of camera up to get an eye in the sky perspective. Whether this is done for aerial photography, FPV flights, movie making or any other reason, multirotors can be a very effective tool for getting a shot that would normally require a full size aircraft or helicopter. In this installment of Multirotor Flight, we will take a look at some of the various types of cameras and camera gimbals that are currently being used on Multirotors, as well as some of the differences between the various items.

With a camera on a multirotor you can capture a lot of interesting shots. These include aerial views of a home or property, overhead images of sporting events or to get an in-cockpit FPV view while you fly. There are an infinite number of ways to put a camera on a multirotor, but for the sake of this article, we will look at some of the most common things that are being done right now. To begin, let’s take a look at some of the popular cameras that available and suitable for use on multirotors.

Figure 1
Figure 1

The first type is the smaller sport action cameras that are very popular today. One of the first models to come to mind in this type is the ubiquitous “GoPro” series of cameras. These little movie-making gems have been around for several years now and have proven themselves through millions of hours of videos. The HD version of this camera was first released in January of 2010 with a 5MP image sensor. This model was followed up in October of 2011 with the improved HD Hero2, which had a higher resolution 11MP sensor in it. The latest version of this camera, the HD Hero3, has a 12 MP sensor, and is available in 3 different models, the White, Silver and Black Editions. The top of the line Black Edition can take video at 240 frames per second, for super slow motion shots, or take regular speed video at up to 4096 x 2160 pixel resolution. These newest versions even include a long range Wi-Fi wireless remote that allow you to start and stop video, or take still shots, from up to 600 feet away! Figure 1 shows this newest addition to the GoPro lineup.

Figure 2
Figure 2

Other miniature sports cameras that are commonly used include the Contour HD series, the Sony Action Cam, the Boscam HD19 and Drift HD series of cameras. All of these cameras are small and light weight, typically 4 ounces or less, and can be directly hard-mounted to the frame of a multirotor. These cameras are priced in the $150 to $400 range, and come with a variety of mounting brackets making it easy to attach the camera to a multirotor frame. Figure 2 shows, clockwise from the top right, several different cameras from Contour, Sony, Boscam and Drift.

Figure-3

The one drawback to any of these types of cameras is that they have an extremely wide field of view, up to 170 degrees on some models, so you essentially see everything from straight up to straight down, and from straight left to straight right, all at the same time. This wide angle of view does introduce some curvature distortion into the picture, especially around the top and bottom of the image. The photo in Figure 3 shows these curvature distortions. The horizon in the center of the photo is straight, while the power lines in the top of the photo bend down on the ends and the railing in the bottom of the image curve up on the ends.

The wide angle of view on these cameras can introduce other problems as well. A common issue is being able to see the spinning propellers in the corners of the video when filming from a multirotor. Unless the camera is mounted out in front of the props, you will always see a little bit of prop in your videos. For some modelers, this is OK, but if you intend on using the video for commercial purposes, the props can ruin the shot. Most of these style cameras have the option to crop the image to a lower resolution, and limit the field of view of the camera down to 120 degrees or even 90 degrees. They do this by just recording the center portion of the image and throwing away the part around the edges. While this can get rid of the props in the edges of the shot, they resulting video is usually a lower resolution image, typically 1280 x 720 pixels instead of 1920 x 1080 pixels. For some this is acceptable, but for others it is not an option.

Moving up in size, the next type of camera commonly used are the mid-size DSLR models. These cameras have much larger image sensors than the ones found in the small action cameras mentioned earlier, so you can get a much clearer, well defined image from them. Most of the smaller action cameras have an image sensor that is only about 6 x 4.5mm in size while most of the mid-size DSLR cameras have an APS-C size sensor, which typically measures about 23 x 15mm. This gives about 14 times more surface area on the image sensor, and this can capture more light for better photos.

Figure 4
Figure 4

Several cameras that have become very popular in this size are the Sony NEX-5 and NEX-7 series, the Panasonic Gh3, the Nikon D7000 and Canon Rebel series including the T2i, T3i and T4i models. Figure 4 shows the Sony NEX-5 camera, which is very popular due to its small body size. These types of cameras feature removable lenses that allow the user can select the best one for the job, depending on the type of shot they need. Since these cameras can all shoot in both still photo and video modes, you can use them to take excellent quality HD video or still shots with 16 to 24 MP resolution, depending on the camera image sensor. These cameras are priced in the $600 to $1500 range, and typically weigh between 12 and 24 ounces, depending on the camera body and lens used. Because of their larger size and weight, these cameras are best suited for larger multirotors in the 650 to 800mm size range.

Figure 5
Figure 5

Going up another size, we come to the full frame DSLR cameras. These cameras have large image sensors that usually equal in size to a 35mm film camera negative, roughly 36 by 24mm, so they are capable of capturing very clear images for both video and still photos. Figure 5 compares the size of full frame sensors to those found in the mid-size DSLR and sports cameras. Here you can see that the surface area of the full frame sensor more than double the area of an APS-C sensor, and 34 times more area than the sensor used in a GoPro camera.

Figure-6

Two of the more popular cameras in this size range are the Canon 5D or the Nikon D4. Figure 6 shows the Canon 5D camera, which is typical of this type. These cameras feature metal bodies, and take larger full size lenses, so they are quite a bit heavier. Depending on the lens used, these cameras weigh between 2.5 and 4 pounds, so you do need a larger multirotor to carry them. Typically, 800mm to 1000mm size hex or octo frames are used for carrying this size camera. These full frame DSLR’s can also get fairly expensive, costing upwards of $5000 for just the camera body alone. Because if this, you will want to make sure that you have an extremely reliable multirotor setup before you risk putting one of these large cameras up in the air!

Moving up from the full frame DSLR cameras are the full cinema grade cameras such as the Canon C300 or Red’s Epic and Scarlett models. The price tag on these cameras, with a matching lens, can top $40,000, so they are typically used only by professional motion picture companies with larger custom built multirotors up to 1500mm in size.

Now that we have looked at several types of cameras, let’s see how to attach them to your multirotor. There are many ways to mount a camera to a multirotor, but it breaks down to two basic types. You can either hard mount the camera in a fixed position to the frame, or mount the camera in some type of gimbal mount, which allows the camera to be moved in flight relative to the airframe. The smaller action cameras, such as the GoPro series, are often hard-mounted to the frame of a multirotor with the mounting kit that comes with the camera. Most of these mounts have a square of double stick adhesive on the base that allows the user to simply stick the camera wherever they need to on the multirotor frame. Most of the camera mounts have the ability to tip the camera up and down a little bit once mounted, but once the angle is set it is fixed for the flight. This does limit the types of shots you get, and as you maneuver the multirotor, the image will tilt and roll with the airframe as the multirotor flies.

To eliminate these issues, and to stabilize the camera, some type of gimbal assembly can be used. A gimbal allows the camera to move with respect to the multirotors airframe, so you can vary the shot without having to actually move the multirotor. This comes in very handy if you want to park your multirotor in one spot using GPS hold, and then be able to pan across a scene in a video. In many cases the gimbal can also be gyro stabilized, so as the multirotor pitches and banks while it flies, the camera stays level with respect to the ground at all times for a level image. Most gimbals have two directions of movement, typically pitch and roll. For yaw control you can simply rotate the entire multirotor. For more control of a shot, some gimbals can be controlled and stabilized in all three flight axes, pitch, roll and yaw.

Figure 7
Figure 7

There are 2 basic types of controls for gimbals, servo driven systems and direct drive brushless motor systems. The servo driven gimbals are typically designed for smaller cameras such as the GoPro and small point and shoot digital cameras. With high quality servos, these gimbals can be set up to operate smoothly, but it is tough to get rid of all the play in the linkages so there can be a little camera vibration. The servos also take a finite amount of time to respond to changes in attitude, so there can be a small amount of lag in the control loop. These gimbals are good for simple camera systems, and can be found in the $100 to $300 range, including servos. When set up properly, these simple gimbals can provide good results for basic shots. Figure 7 shows a simple servo driven 2-axis gimbal.

Brushless direct-drive gimbals are a more recent development, and there have been a large number of them introduced recently. Because the brushless motors that drive the gimbal are directly connected to the camera mounts, the response of these gimbals is virtually instantaneous and very fluid. When properly set up, the multirotor can make violent changes in pitch and roll, but the view from the camera remains unchanged. DJI has several brushless gimbals available that are popular. Their Zenmuse gimbals are available for several different midsize DSLR cameras including the Sony NEX-5 and NEX-7, as well as the Panasonic Gh2. These gimbals work exceptionally well, but they are a bit on the expensive side with a $3,500 retail price tag. DJI recently released a new brushless gimbal for the GoPro Hero cameras that allows them to be attached to their smaller RTF Phantom quadcopter, or any other smaller size multirotor frame. The retail price of this gimbal is $699, and can be seen in Figure 8. There are many other brushless gimbals that are currently in development, and like everything else, as more manufacturers make these items, the prices of them will come down.

Figure 8
Figure 8

Another type of camera used on multirotors are the FPV systems. These have been around for quite a while and are extremely popular for getting a “from the cockpit” view as you fly your multirotor. Many of the smaller sport action cameras have the ability to record HD video and simultaneously send out a lower resolution live video stream that can be broadcasted back to the pilot via a telemetry transmitter, so they can double as an FPV camera. Back on the ground, the pilot can see the video from the camera in several different ways including small video monitors attached directly to the transmitter, larger video monitors set up for multiple people to view, or in video goggles that are directly worn over the pilots eyes while flying. This type of flying give a very interesting perspective, as if you are sitting in the aircraft while you fly it, so if you ever get the chance to go on an “FPV ride” with someone’s model, be sure to give it a try. One word of caution though, if you have never done this before, it is best to sit down in a chair for your first FPV ride. When you lose your normal view of the outside world while wearing FPV goggles, the banking of the view can trick your mind into thinking that you are falling over with some rather embarrassing results!

Cameras can add an entire new perspective to your multirotor experience, and provide some interesting new ways to use your model. If you have not tried FPV flying or filming from your multirotor, be sure to give it a try. It adds an entire new dimension to your flying experience.

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