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Tuesday, February 25, 2014

Get Above It All, Part II

This is the second in a series of articles on aerial imaging using drones. In this issue, we look at gimbals, FPV and aerial imaging techniques.

Labels: Gear
This Article Features Photo Zoom
Framing And Composition
The first time I put a camera up in the air on a quadcopter, I was elated, but I also felt totally blind. I was successfully taking aerial pictures and video, but I couldn't control the camera and couldn't see what it was capturing. To apply your photographic eye to aerial composition, you'll want two important upgrades to your aerial imaging rig.

The first is camera-orientation control. Fortunately, all gimbal controllers have this sort of control built in, and if you have a radio transmitter with an extra channel, all you need to do is connect an output from the flight controller or radio receiver to the appropriate input on the GCU. If you went with the Zenmuse and Phantom Upgrade Kit, you're in luck. The kit includes hardware to provide access to the transmitter channel that controls pitch (tilting the camera up and down), and the Zenmuse gimbal will just work when you start using the new control on the transmitter. If you're mixing and matching your own hardware, you'll need to work out your own solution. Luckily, much of this is documented online, and with a bit of web research, you'll find instructions on how to do it (wiring and soldering skills are required). You can also have your local RC dealer do the installation for you.

The second part of successful aerial composition is real-time framing via a video signal from your multirotor's camera. This is commonly called "first-person view" (FPV), and the incoming video signal is displayed on LCD monitors (typically, 7 to 10 inches) or LCD glasses, allowing a pilot to fly as if he or she was looking out of the front of the aircraft. Flying FPV is very similar to playing a video game using a joystick, and it's not uncommon to feel like your aircraft is a flying avatar capable of capturing images from anywhere!

Getting an FPV setup working can be complicated, but the principles are simple. Find your camera's analog video-out signal and connect it to a video transmitter (websites like ReadyMadeRC sell GoPro cables for this purpose). On the receiving end, use a compatible video receiver, and plug its video output into your chosen display device. Common consumer brands for FPV are Fatshark and ImmersionRC, and companies like DJI also offer FPV solutions.

Both of these aircraft upgrades are currently firmly planted in the hobby world. It can take a lot of research to understand how exactly to perform these modifications yourself, but if you enjoy building things, it can also be a lot of fun. As mentioned previously, you can also just buy an off-the-shelf dealer package that incorporates everything we've talked about so far.

LayerLens for GoPro
Two accessories are especially useful for aerial imaging using multirotors. The first is a polarizer for your aerial camera, which is particularly helpful if you're shooting over water. You have to be careful when adding accessories and using a gimbal because gimbals are designed to work with perfectly balanced loads. Putting an accessory lens on a GoPro, for example, moves the center of gravity, which strains the gimbal's motors. In extreme cases, this can cause motor burnout. Because of this constraint, I recommend using the lightest polarizer possible. For GoPro cameras, a product called LayerLens combined with a circular-polarized lens replacement is the perfect solution. At 7.5 grams in weight, it barely adds any weight to the camera, and I've done numerous flights without any problem from my gimbal. Having said that, you should be aware that these gimbals don't officially support modified GoPro cameras, so you'll be using accessory lenses at your own risk.

The second must-have accessory is a replacement charger for your multirotor's batteries. Many chargers are DC-only, requiring a DC power supply to work, but I recommend getting a charger that accepts both AC and DC so you can just plug it into your wall. Optionally, you can use a car battery or other 12V power source if you want to charge in the field. The HITEC X4 AC Plus 4 Port ACDC Multi-Charger is excellent, charging up to four batteries simultaneously and supporting storage charging, a recommended voltage level for safe, long-term LiPo battery storage.


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