360 degree panorama of the End of the Ash River Trail: (click on it for a larger image)
If you have been following me at all concerning my adventures into multi-rotor platforms for photography you may already know that I was pursuing a rock steady stable platform from which to take aerial photography shots from. Videography is definitely a back burner issue with me, my main interest is with still photography.
My initial disappointment was with the DJI Phantom 2 Vision in that the camera was rather poor quality, at least when measured against professional photographic equipment. The dynamic range was low, the lens was too wide an angle, the fisheye aspects were unacceptable, and worse the images from this camera were difficult at best to correct for image distortion.
I almost immediately sought out alternatives, the Go-Pro was also unacceptable to me since it also has a pronounced fisheye look to its images. Initially I adapted my Nikon J1 camera to the Phantom but found that it was simply too heavy to be safely flown with the Phantom. After exploring other avenues I found that I would have to spend over five grand to get a decent platform that could safely lift my Nikon J1, let alone my intended camera, my Nikon D800.
I was searching for a cost friendly alternative so I first built a quad using DJI’s E800 motor/ESC combination but found that these motors don’t come close to their advertised thrust in their “Tuned Propulsion System” it should, in all honesty, be called the Detuned Propulsion System. So I set out to build my hexacopter.
I was having troubles tuning the necessary vibration isolators to prevent the inevitable resolution robbing vibrations away from the camera. I was even looking to scrap my drone program entirely in favor of a balloon based system which has very little or no vibrations at all.
Then it dawned on me after a test flight. I have used tie cord as a safety backup in case the vibration isolators would become separated from the camera platform and after a previous hard landing all four indeed became detached. The next flight I forgot to reattach the isolators so the platform was hanging by the tie cord loops. The four tie cord loops were not all equal in length so the camera was flown at a ten degree, or so, tilt angle. After landing and giving my self a Homer Simpson DUH! I decided to download the flashcard and see what I got.
To my surprise the sharpest images that I have taken to this day from any aerial platform! That was the key! For the first time I was able to stitch a decent ten image panorama together! The problem with fisheye lenses is that they don’t stitch into decent quality images very well. Even though the camera was tilted and the copter wavered around due to both the normal GPS wondering and well as the ten to twenty MPH gusty breezes my stitching program, PtGui Pro, was able to easily stitch the ten images together. The other main problem with this particular panorama is that I did not take the images with enough overlap. While there are some areas of the image that certainly need improvement it is the IMAGE RESOLUTION that beats all previous images taken from any ariel platform, at least by myself!
Next to stabilize it even more I will be looking into a downward facing stabilization camera to supplement the GPS for position hold as well as an ultrasonic range finder to supplement the altitude hold function. Using vibration isolators between the camera platform and then suspending the gimbal from the airframe with tie cord is a perfect answer for total vibration isolation for still imagery, while this is obviously not a very good solution for videography – well I really don’t care that much about moving pictures anyway 😉
Update: I may have spoken too soon when suggesting that tie cord may not work for video, here is a video taken with the exact same setup as was used for my stitched pano:
You can clearly see the difficulties in taking a series of still images to stitch together for a pano, the copter is flailing around in the wind. Most of the jitteriness seen in the above video would be minimized when a two axis stabilizing gimbal is utilized. Note that the video from the Nikon J1 is not very good to begin with, compared to the D800, slow panning on a stationary tripod results in marked loss of resolution, not seen at all in this video. I am becoming convinced that a third axis gimbal motor may be necessary due to the unreliably unstable rotation control of the hexacopter is around the z-axis, especially when windy. Yup, retractable landing gear and a third axis gimbal motor may ultimately be necessary.