A kite aerial photography field report
Date of flight: January 27, 2013 Site: North Branch Nature Center, Montpelier, Vermont Occasion: Ice on Fire deep winter celebration
Each winter, right around the traditional Gaelic celebration of Imbolc, http://en.wikipedia.org/wiki/Imbolc, Montpelier, Vermont hosts a deep winter festival dubbed Ice on Fire, www.facebook.com/pages/Ice-on-Fire-Central-Vermont-Winter-Festival/136583219729210. Set in a field at the North Branch Nature Center, http://northbranchnaturecenter.org/, the festival includes an opening parade, winter games (three-legged snowshoe race, anyone?), theater, song, and storytelling. In the midst of everything is a roaring bonfire. In other words, fascinating subjects for kite aerial photography!
The story behind the pictures
Kite technical notes
Camera and photography technical notes
About the authors
The story behind the pictures --by Carl Etnier and Kalyn Rosenberg The two of us mounted our second-ever KAP expedition on Sunday, January 27 at Ice on Fire. We're still very much in the experimentation and learning phase of KAPping, and the day was a success in locating things to improve with the set-up! We also found that a bit of good luck can (sometimes) compensate for even multiple mistakes.
One of the goals was to test the limits of the equipment in cold weather (13-14 F) and a location in a valley, sheltered from winds. Winds were recorded as 10 mph at the Montpelier airport during that time, and the airport is sited in open terrain around 600 feet higher than the Nature Center where we were flying.
The camera performed surprisingly well, taking over 600 shots over 45 minutes in the cold, with almost half the charge left over in the single pair of rechargeable AA batteries. Winter KAP is indeed readily doable at temperatures well below the minimum operating temperature specified in this camera's manual. (See below for technical notes on the kite and camera.)
We launched from an area a hundred feet from the Ice on Fire "village," where the snow had been packed down to make a course for the kids' three-legged snowshoe race. The low winds were challenging at first. We started flying the 9-foot Levitation Delta Kite, http://intothewind.com/shop/Traditional_Kites/Delta_Kites/ITW_9-ft._Levitation_Delta_Kite, just before 2 pm, but the early flights were short. The wind was light, with mild gusts. We would get the kite into the air and give it maybe a couple hundred feet of line, and then the wind would drop to the point that the kite would slowly drift earthward. Sometimes the kite came all the way back to the ground, and sometimes we managed to pilot the kite back to a reasonable elevation and taut line. We launched the kite at least a half dozen times.
The wind picked up just enough by 2:45 or so to keep the kite reliably in the sky and even generate some significant lift. After five minutes or so of steady wind, we decided to try hoisting the camera. We used a Canon PowerShot A720 with the CHDK firmware hack, http://chdk.wikia.com/wiki/CHDK, in a PET bottle and rubber band rig, dangling a couple feet below the kite line. The camera was programmed to take three pictures every five seconds, and it was angled a bit away from straight down.
Wandering through the Ice on Fire "village," we found people were delighted both at the spectacle of a 9-foot kite and at learning that there was a camera on the kite string. Lots of people waved at the camera or otherwise mugged for it. A few kids asked if they could fly the kite, but we politely explained that we were in the midst of a photography session. (If we allowed anyone else to fly the kite even briefly, it was likely we'd be swarmed by kids asking for their turn, and it would be very hard to get back on track.)
The technique was to walk ten feet or so, stop for a while--to allow the camera to take some shots without the extra joggling from the walking--and then walk on.
After our perambulations were wide enough that we were satisfied we had photographed most of the area, we walked the kite back to the launch field and reeled the camera in. It had shut down, which didn't surprise us, given our concerns about battery life in cold weather. What surprised us was that when turned back on, it showed 100% battery strength and only a few score photos taken. (See the technical note, below, for the reason.)
We started the camera going again and let the kite back into the air. This time we covered less territory, in part because we were beginning to lose the wind. At one point, when the camera was over the central bonfire, the wind dropped fairly quickly, and we ran the kite away to a place where the camera could gently crash to earth without hitting anyone or being incinerated. We quickly got it launched again, though some bits of snow at the outside of the lens show up in the subsequent shots.
Mostly we kept the camera pretty low, to get details. Before finishing, we let out all 500 feet of line to send the camera as high as it would go with that set-up. Unfortunately, the highest altitude shots may be ones showing only unpopulated parts of the field.
When we pulled the camera in for good, the camera was still taking three pictures every five seconds. We were just eager to drink some hot cider and observe the festival from the ground, without the distraction of a kite and camera on a string. The camera took a total of 637 shots that afternoon, with power to spare in the two AA batteries.
More of the day's best shots are, for now, at https://www.box.com/s/7xd84pmjhinsr7cvjule. (Please credit Carl Etnier if you use them anywhere.)
One thing that jumps out from the photos is how pronounced shadows on snow are when seen from the air at 3:20 pm on a late January day in Vermont. One of the consequences was that the kid being thrown on the blanket is invisible in the darkness of the blanket's shadow in most shots; the one above, which catches him in mid-air, is one of the few where he's visible. Viewing the scene from the ground, we did not notice how long the shadows were.
We're complete newbies at this, so any constructive comments or advice is appreciated!
Kite technical notes --by Carl Etnier Kite: Into The Wind's 9-foot Levitation Delta The central section of the kite's three-part cross spar broke the week before this outing, on the kite's third flight. Winds that at that time were 17 mph, with gusts to 25 mph, according to readings at the airport, which is at a nearly identical elevation nearby. The kite is rated for winds of 4-20 mph. Brandy at Into The Wind agreed to replace the piece under warrantee, but cautioned me to be careful, as she'd only do that once. (Fair enough, I thought.)
With the light winds at Ice on Fire, I tried to replace the cross spar with a ¼-inch dowel. The dowel broke as I was inserting it into the kite. Next time, I'll try a beefier dowel and/or reinforce it with a wrap of strapping tape every few inches.
With the lighter dowel broken, and the replacement not yet arrived, I flew with a cross spar I'd constructed out of three tent poles. It is somewhat heavier than the original (4 oz. vs 3.5 oz. on an imprecise 10-pound kitchen scale) and appears considerably thicker.
One endearing characteristic of this kite is its ability to gently float downward when the wind dies, rather than pitching downward rapidly. It's like it turns into a parachute when it lacks enough wind even to lift the line. Occasionally the nose tips down briefly in a stall, before it rights itself again, but the kite can just float in the air with the line slack on the ground. The extra time in the air means that if the wind picks up again within a short time, the kite is already in the right place to catch the wind; no relaunch required.
Camera and photography technical notes --by Carl Etnier Camera: Canon A720 with CHDK Weather: Sunny, 13-14 F recorded at Knapp State Airport (600 feet higher elevation); winds 10 mph at the airport
I was very satisfied with the quality of pictures taken, but only dumb luck was responsible for the exposures being right. The settings used were not the ones I'd intended.
I had planned to set the shutter at 1/800 and let the camera choose the aperture in the camera's Tv mode. Further, I thought I was bracketing each shot with two other shots at aperture settings +/- 2/3, using the method of “Make ANY Single-Shot Intervalometer into an HDR- Bracketing Script, http://chdk.wikia.com/wiki/UBASIC/Scripts:_Make_ANY_Single-Shot_Intervalometer_into_an_HDR-Bracketing_Script, .” (The high contrast of bright snow and dark shadows seemed like an especially important situation to bracket in.) Neither plan worked out.
What went right: I did get the basic CHDK Intervalometer script working properly, set for 5 seconds. And ISO was set at 80, which I'd intended.
What went wrong: First, I put the camera on M mode, instead of Tv. That meant that not only was the shutter set at 1/800, but the camera would not change the aperture according to light conditions. It happened to be set at f/4. Furthermore, I had checked a box in the CHDK bracketing menu that turned off the bracketing settings when the camera powered down and powered back up. The camera still took three pictures every five seconds instead of one, but all three pictures used identical settings. Every single one of the 637 pictures shot was at 1/800 and f/4.
Luckily, conditions were pretty good for 1/800 and f/4 at ISO 80.
I was amazed at the life of the batteries in the cold. I used two freshly charged Eneloop AAs and never needed to swap them out. I turned the camera's display off before starting the intervalometer, but I forgot to use the Menu button to turn Review off, so each picture was displayed in miniature for a couple seconds after it was taken. Even so, the camera was still shooting when we reeled it in the last time, and CHDK's battery meter indicated 44% charge remaining. (When I got the camera back home and at room temperature, the meter indicated the batteries still had 94% charge.)
The camera was out in the cold for 45 minutes, and the second, much longer round of shooting lasted for 20 minutes solid.
The camera's documentation indicates its minimum operating temperature is 32 F, 18 F higher than the day's high temperature.
A significant hindrance due to poor camera design occurred when I was trying to attach it to the PET flask rig. I would start the camera shooting and, as I manipulated it into the PET flask rig, a bunch of times I brushed the on/off button on top and turned the camera off. There are no air photos from the first round of shooting, when we walked around more of the area than in the second round. Since there are a bunch of photos from the beginning of the first round, showing the camera's view of my hand inserting it into the PET bottle rig, I am convinced that I inadvertently turned the camera off just before releasing it on the kite string.
I have now made the on/off button much more difficult to hit accidentally by taping a piece of firm, clear plastic over it. I used the stiffest one that I thought would still allow me to easily push the button when I wanted to--not quite as stiff as a 2 L PET bottle, but almost. I haven't stuffed the camera into the PET bottle holder yet with the plastic in place, but I have tried quite hard to "accidentally" trigger the on/off button while manipulating the camera. No “accidents” have happened.
I've also added a pair of binoculars to my KAP equipment checklist. With that, I hope to be able to see whether the camera is still firing without reeling it in, either by spotting the extended lens or by seeing the orange light on the front of the camera that flashes every time the shutter closes.
The PET bottle rig is designed for protecting a camera that points straight down, which is the ideal position for mapping. I jammed the camera in at an angle (maybe 15-25 degrees from vertical) to get what I hoped would be more visually interesting shots at this venue. I cut away part of the PET bottle do so. Still, the photos had a quality pretty close to looking straight down. It would be nice to figure out how to provide the protection of the PET bottle rig while setting the camera at a more oblique angle.
Also, the camera was zoomed all the way out, to 35 mm lens equivalent. For shots at a winter festival, I'd like to be zoomed in a bit more, to get more detail. But the jiggling of the kite line may make it harder to take sharp photos when zoomed in more. Next time, I'll maybe try a round with the camera zoomed to 50 mm lens equivalent and see what happens.
I'm looking around other winter festivals in open areas, to put all these lessons learned into practice and find out what new things can go wrong.
Checklist for using the camera in the field Checklists of actions are important for getting things right. They're widely used by pilots, and doctors are starting to embrace them, http://www.indiebound.org/book/9780312430009, . If I'd had a complete and correct checklist on this flight, I would not have relied on dumb luck to get good photos. Here's the checklist I'll take with me in the field next time--it's a little long to keep in one's head. With this checklist, a Canon camera set up with CHDK, and a PET bottle and rubber band rig to attach the camera to the kite line, I can set the ISO and shutter speed I think are appropriate for conditions and allow the camera to choose the right aperature. To allow for tricky light conditions, like dark objects on snow, or to make high dynamic resolution photos possible, the bracketing method selected takes a total of three shots: one allowing the camera to choose the aperature, and one each with the same ISO and shutter speed but the aperture 2/3 greater or smaller than the basic shot.
- Turn camera on
- Check that lens cover opened completely
- Check that battery charge is at 100%
- Set dial to Tv mode
- Use the <-- or --> button to set the shutter speed, say to 1/640 or 1/800
- Hit Function Set and set ISO to 80 or 100
- Set drive mode to Continuous
- Hit Function Set again to leave that set of menus
- Check that red text in the upper right corner of the display reads "Bracket: +/-" and "AV: 2/3Ev". If not, follow the indented instructions. Otherwise, skip them.
- Hit ALT then Function Set to enter CHDK scripts
- Check that Intervalometer script is selected and interval is set to 5 seconds
- Select Remote Parameters --> Bracketing in Continuous Mode
- Check that Tv Bracketing Value is Off and Av Bracketing Value is 2/3 Ev
- Check that Clear Bracketing Values on Start is not checked
- Hit ALT twice, to leave CHDK menus and re-enter ALT mode
- Skip the next 3 steps and go to "Push the shutter button once," below
- Hit ALT then Function Set to enter CHDK script mode
- Check that Intervalometer script is selected and interval is set to 5 seconds
- Hit ALT twice, to leave CHDK script mode and re-enter ALT mode
- Push the shutter button once. When the camera takes 3 pictures, hit the shutter button again to interrupt the bracketing script
- Put camera in Playback mode using the switch in the upper right corner.
- Hit ALT to leave CHDK mode
- Review the last 3 photos to make sure that bracketing worked.
- If not, troubleshoot. Otherwise, continue.
- Switch back from Playback to Shooting mode.
- Hit Menu
- Scroll up to Review and set it to Off
- Hit Menu to leave that set of menus
- Hit DISP to turn off display
- Hit ALT to enter CHDK mode
- Put the camera into the PET bottle rig
- Attach the PET bottle rig to the kite line
- Hit the shutter button and check the orange light on the front to make sure the camera is shooting.
- Give the kite some line and let it fly!
The authors would like to thank Public Laboratories volunteer Chris Fastie for much encouragement and helpful advice as we ventured into KAP.
About the authors Carl Etnier enjoys viewing the earth from above, http://www.indiebound.org/book/9780810934955, . He used to fly a Rally 2B, http://lightsportaircraftpilot.com/rotec_rally2b_ultralight_aircraft/pictures.html, ultralight airplane but now looks for less carbon-intensive ways of flying, actually or vicariously. He has tried his hand at hang gliding and paragliding, and would do that again, but now he mostly views the world from above by hiking ridgelines, living on a hill, and starting this year, by sending a camera aloft.
Kalyn Rosenberg, Vermont Community Organizer of Toxics Action Center, www.toxicsaction.org, can be found poring over kite and camera specs as she prepares to buy KAP equipment for use by grassroots environmental organizations in mapping projects. Toxics Action Center is a public health and environmental non-profit that works side-by-side with residents to prevent or clean-up pollution. Toxics Action Center is working to connect ad hoc community groups to tools developed by PLOTS to help advance their local campaigns.