The View Up Here

Random scribblings about kites, photography, machining, and anything else

Posts Tagged ‘Brooxes’

Panorama Workflow

Posted by Tom Benedict on 23/07/2010

I’ve had some opportunities to play with my camera on the ground as well as in the air, and to test a number of image sets on the software I’ve been using.  Two days ago my wife and I took our kids to Pololu Valley to go hiking.  On the off-chance the weather would be nice, I brought my KAP gear.  The weather was fantastic, with solid winds for kite flying, and beautiful partly-cloudy skies.  Time to play!

I ran about 5GB of images through the camera from various vantage points.  In creating the base images I tried to incorporate everything I had learned from the earlier experiments.  The resulting photographs turned out quite well, so I’m considering the new workflow to be a win.  I’m sharing it here in the hopes that someone else doing kite aerial photography will give it a try and take it even further.  Here are the details:

  • If you can shoot RAW, shoot RAW.  I can’t, but in the near future I’ll be able to.
  • Use Manual Exposure mode on your camera.  Set it on the ground, check it, and double-check the histograms to make sure you’re getting bullseye exposures.
  • Use at least 1/1000 second exposure speed.  I’m using 1/1250.
  • Use the slowest ISO setting you can to control noise.  This is of less concern with a DSLR, but every bit helps.  I made this set at ISO 80.
  • Use the sweet-spot aperture on your lens if possible.  My lens is sharpest around f/4 to f/5.  I couldn’t use this aperture and hold the other numbers, so my lens is wider than ideal.  But the benefits in noise at ISO 80 make this a reasonable choice.  I give up some sharpness for lower noise, and keep the fast exposure speed to avoid blur.

Once the camera is in the air, all my panoramas were made with the camera vertical.  With a KAP rig this either means building the rig around a vertical camera (Brooxes BEAK rig), or using an L-bracket on a conventional rig, or having a dedicated Horizontal/Vertical axis on the rig.  I recently modified my rig to add the HoVer axis, so this is the route I went.

The idea with this technique is to start the rig on a slow spin, and to trigger the shutter continuously.  This technique was developed by a French KAPer who goes by the name of Vertigo on the KAP forums.  With a sufficiently fast shutter speed, this works perfectly.  My A650IS does one frame every 1.1 seconds.  With a 10-second-per-rev rotation rate, this works out about perfectly.  I’m upgrading to a Canon EOS T2i DSLR in the near future, which has a much faster frame rate.  I’m planning to build an electronic release cable for this camera that will give me the same 1-frame-per-second rate my A650IS has so I can continue to use this technique.

  • Start the rig rotating at a rate that gives you adequate overlap between images, and minimizes motion blur from the rotation, given the camera’s shutter speed.
  • Once the camera is rotating cleanly (no see-sawing on rotation, no jerkiness in the pan axis, no swinging around, etc.) trip the shutter.
  • Make at least two complete orbits of the camera, tripping the shutter non-stop the entire time.  This is for a couple of reasons:  First, it gives you plenty of frames to choose from in case one is blurry.  Next, it gives you a range of random tilt angles that you can use to fill in gaps later on.  Finally, if the rig starts to move, the second orbit will still produce a clean panorama.
  • If you want to make a larger panorama, change the tilt after two orbits and make two more orbits at the new tilt value.
  • While all of this is going on, do everything you can to minimize camera motion.

This should produce a nice set of images from which to work.  You may well end up using them all, so don’t toss any of them!

I use Autopano Pro for stitching.  Some of the tricks I’ve picked up will apply to other packages.  But if you find yourself scratching your head and thinking, “No, I’ve never seen that,” don’t sweat it.  Your software is different.  Skip that part.

One of the first problems I ran into is that Autopano Pro deals really well with point features, but not very well at all with linear features.  For example, it’ll match up individual stones on a beach like a champ, but it will produce lousy horizons if the horizon is just water and sky.  It makes no effort whatsoever to correct for lens distortions if the bulk of the picture is water and sky.

The fix I found was to use PTLens to correct lens distortions before using Autopano Pro.  PTLens is a $25 plug-in for Photoshop.  Even better, it’ll run as a stand-alone program and will batch process hundreds or even thousands of images at once.  If you’ve got a block of images you photographed as fodder for panorama stitching software, it’s no problem at all to batch process them all to remove lens distortions.  Water horizons should now be ramrod-straight lines across the frame.

So back to the process:

  • Run the entire image set through PTLens to remove barrel distortion, vignetting, and chromatic aberrations, but nothing else.
  • Process the images with Autopano Pro, or the panorama software of your choice.
  • Do everything you can to get completely horizontal, completely straight horizons for water.  Nothing kills a pano faster than a grossly errant horizon.
  • Save as 16-bit TIFF images.  16-bit workflow can be a real PITA, especially on a smaller machine, but it hides a lot of ills when it comes to large-scale processing like Levels and Curves.

At this point I open up the images in Photoshop.  I’m still using Photoshop 7.  I’ll upgrade to CS5 as soon as I can afford it.  But for now it still does everything I need.  Want is a whole ‘nuther story, but as far as my needs go, it’s fine.

  • View 100% and check for stitching errors.  Repair all of these with the rubber stamp or heal tools.
  • If your kite line shows up in the image, remove it using the same tools.
  • If you cropped your panorama wide enough to have gaps in ground or sky, open up all the images that went into the panorama, as well as the second orbit you made from that same location.  Use the rubber stamp tool to pull patches from any and all of the input images to repair problems on the panorama.  (This is one of the best reasons to make a second orbit!)  Since you used a fixed exposure, you should be able to rubber-stamp these into the panorama with no changes necessary.
  • Once the panorama is defect-free, look at your levels.  If you did your job setting the manual exposure on the ground, the exposure should be dead-nuts on, or need very little tweaking.
  • Do all your dodging and burning at this point to get the exposure just the way you want.  This can involve lots and lots of time, depending on how meticulous you are with your exposures.  If you’re the kind of person who got into photography in the days of film, and spent your afternoons in the positive darkroom dodging and burning the same negative over and over and over, you may be on this step for a while…

At this point the bulk of the workflow is complete.  But I would advise you not to stop here.  In Photoshop under the File menu is a command called File Info.  Click it.  It lets you edit the header information associated with your image.  At the very least I would fill out:

  • Title – What is the name of the original file on your computer?  Leave out the extension since that can change without changing the image.
  • Author – Your name.  You’re the author of your image.
  • Caption – Describe the photograph clearly and concisely, and include enough information so that you could read it and know where on the planet you were when you made the photograph.
  • Copyright Status – Change this to “Copyrighted Work”.  The moment you tripped the shutter, your photograph was a copyrighted work.  Not marking this just sets you up for someone to use your photograph without your knowledge.  If you choose to license your photographs under the Creative Commons license, of course, you should set this appropriately.
  • Copyright Notice – Mine reads: Copyright © Tom Benedict
  • Date Created – The date you tripped the shutter on your camera to make the photographs that went into this image.
  • City / State / Province / Country – Fill them in.
  • Source – Give yourself some hints here.  Is it a straight shot?  Digital?  Film?  Stitched?  My digital panoramas are all marked “Digital-Stitched”.

The neat thing is that most of the photo sharing sites on the Internet will automagically read your header information and fill in their own forms for you.  You may still want to provide more information than this, but the base information will be there.

The even neater thing is that in the event someone downloads your photograph and puts it on their own site without your knowledge, your header information is indexed by most search engines.  Even better, when you challenge them and they claim the photograph as an “orphaned work”, you can demonstrate that they did not make an honest effort to find the photographer in order to ask for permission since your info is all right there with the image.

So that’s it in a nutshell.  How well does it work?  See for yourself:

Pololu Valley Wetlands 2

– Tom

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A KAP Rig for Panoramas

Posted by Tom Benedict on 30/04/2010

I finished the modifications to my KAP rig to give it an additional axis of rotation: plan.  With the flip of a switch, I can rotate my camera 90 degrees for doing verticals or for making vertical panoramas.  The additional axis was almost entirely constructed using parts from Brooxes.  The only custom part could be replaced with a slightly modified commercial part.  Here’s the axis as-built:

HoVer Axis

The modification didn’t really add that much weight to the rig, but it did add a considerable amount of bulk. I didn’t really pick up on how much until I rotated the camera to vertical:

Subtle as a Dump Truck

I modified my transmitter by removing one of the unused axes and installing a TPDT switch in its place. Two 10-turn 5k potentiometers wired on either side of the switch give me two independent set points I can switch between. One was set to position the camera horizontally, and the other was set to position the camera vertically. The 10-turn potentiometers allow plenty of room for fine-tuning and dialing the HoVer axis in really accurately.

Sit 'n Spin

I haven’t had an opportunity to fly it yet, but that should come over the weekend.  The only other modification I still need to make is to add provisions for my safety lanyard, which is shown hanging in the wind here, and to add Velcro safety straps for the camera itself.  My previous method for strapping the camera down would interfere with the new HoVer axis.

The parts used for the HoVer axis are a Brooxes Utility Frame, a Brooxes Deluxe Gear Guide, and a custom hub.  The reason for the custom hub was to provide a positive connection between the camera bracket and the HoVer axle.  Using a plain-shaft hub runs the risk of having the set screw come loose and the camera falling free of the frame.  So I made a hub with a threaded hole in the middle.  This screws onto the HoVer axle, and a set screw then locks it in place.  If you’d like to make this modification to your rig and don’t have a machine shop to make parts in, a good alternative would be to pick up a 1/8″ bore gear hub from Servo City, enlarge the bore, and tap it #8-32 to go on the Deluxe Gear Guide axle.

One unanticipated benefit of this is that attaching the camera to the rig is very straightforward now.  The camera can rotate in all three axes, so it’s a simple matter to flip the camera on its side, roll it back a little, and really get some easy access to the tripod screw.

I can’t wait to get this rig off the ground and see what Autopano Pro does with the resulting photo sets.

– Tom

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Return to Kiholo Bay

Posted by Tom Benedict on 08/09/2009

I’ve flown a camera at Kiholo Bay a number of times now, but for some reason I’ve never been all that overwhelmed by the sweeping landscape pictures I’ve come back with.  They’re either too long and narrow, or don’t really capture the sense of the place, or are just plain awkward.  In a way this may explain why I keep going back.  But when I do go back, I tend to photograph it the same way.  Photography is one of those things where living in a rut just doesn’t work out in the end.

Rather than repeat what I’d done before (ok, rather than repeat my mistakes) I decided to take a fresh look at the problem:

Kiholo Bay is a gorgeous stretch of water just south of Anaehoomalu Bay.  It’s got a fantastic reef, a really good view of Hualalai, and the inlet is one of the most striking features on that entire stretch of coast.  It’s one of the few spots along the Kona coast of the Big Island that has a scenic lookout.  So what was missing?  I realized I’d been focusing on the inlet at the expense of everything else!  Once I decided what I wanted to include in the frame, it was a matter of figuring out how to do it.

I decided I wanted the inlet as a diagonal slash across the bottom of the frame, with the reef getting plenty of space.  I wanted a horizon line that included Hualalai, the volcano above Kailua-Kona, a really clean sky, and the whole stretch of shoreline along Kiholo Bay.  With that in mind I pulled up Google Earth and started fishing.  In the end I also wound up going back to some of my earlier photography there, but in the form of a Photosynth.  This combination of tools and ideas gave me what I wanted: a vantage point.

There’s a spot about five hundred feet north of the inlet, about four hundred feet inland, and roughly three hundred and fifty feet above the ground that would give me the angle I wanted.  You could do it from a helicopter with FAA clearance to fly at that altitude over what is admittedly not a populous area, but it’s a lot easier to do this sort of thing from a kite.

The mornings have been sparklingly clear, but by mid afternoon the volcanic gases coming out of Kilauea creep north of Kailua-Kona and cover the Kona coast in a thick haze.  It can make going to the beach less than pleasant.  But it makes photography downright impossible.  The ideal time of day for the picture I wanted was about an hour before sunset.  But waiting for the light meant losing the atmosphere, so I opted to go early in the day.

Monday was a holiday, so I checked the local weather conditions.  By 10am the wind around Kiholo Bay was supposed to be four knots onshore with little to no turbulence.  Perfect for slack-line flying, and ideal for a picture of this kind.  I grabbed my gear and headed out.  It’s a half hour drive to Kiholo Bay, and another half hour hike across the lava.  By the time I reached the water I realized something was terribly wrong.  My four knot steady onshore wind was more like a two to ten knot gusty down-shore mess.  It was with some trepidation that I pulled out my rokkaku and got my camera airborne.

It wasn’t the steadiest flight in the world, and at one point my rig came down and landed hard on the lava.  Some recent modifications to my rig made for a safer landing, but my heart was still in my throat when I saw it sink behind a ridge and felt the line go slack.  But seconds later it was airborne again, and I was able to reel it back in and check it out.  Everything worked perfectly.  I didn’t even bend the leg brackets on my rig.  It’s a testament to the good design work and engineering Brooks Leffler puts into his KAP rig products.

I knew the field of view I needed for the picture, and knew my camera didn’t have a wide enough field to pull it off.  So I planned to use stitching software right from the start.  This was important to know, because the methodology is different when going for individual frames and composites.  This time I wanted a composite.  Rather than use the tried and true Gigapan style pattern that most KAP panoramas are made with, I used a modified version of one pioneered by Vertigo, one of the French KAPers: burst KAP.

In traditional KAP panorama work, the rig is pointed in one direction, stopped, and a picture is taken.  The rig is then tilted down slightly and a second picture is taken.  This process is repeated until the camera is pointed vertically.  At that point the rig pans to a new “slice” location and the process starts over.  With a good camera and rig, this takes roughly five seconds per shot.  For a ten shot composite, it’s almost a minute of photography.  A KAP rig can move a lot in a minute.

In burst KAP panorama work, the rig is set to spin on its pan axis, and frames are fired off as fast as the camera can take them.  A combination of high shutter speeds and carefully calculated pan speeds makes for very fast, but still quite sharp work.  In this case I needed more height than my camera could give me, so I did the burst in two passes.  To be more accurate I did it in four passes, starting with the camera horizontal and ending with it near vertical, making a single pass with the pan axis for each tilt angle.  In post-processing I only used the first two tilts, however.

Rather than waste a trip, I photographed Kiholo Bay this way over and over as the kite and camera moved around the sky because of the shifting wind.  The end result is that I made numerous burst KAP sets with the camera at a variety of altitudes.  When I got home it was a matter of choosing the set that gave me the angle I wanted.  Nine images, taken over roughly fifteen seconds, supplied the imagery necessary to build the composite I had imagined.

Kiholo Bay

The final image came out at 9057×4800 pixels with no stitch errors during compositing.  This is sufficient to print it 60×32″ with no visible pixelation.

I truly enjoy the serendipitous moments that happen when doing photography in general, and KAP in particular.  There’s a particular smile I’m sure every photographer wears when they go through their pictures at the end of the day and find something they really weren’t expecting.  But there is a great deal of satisfaction to be had from thinking through a photograph, planning the composition, and then pulling it off despite not having things go quite as expected.

– Tom

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KAP at Hawaii Volcanoes National Park

Posted by Tom Benedict on 24/06/2009

For a long time, it has been a dream of mine to do KAP at Hawaii Volcanoes National Park on the Big Island of Hawaii.  I’ve wanted to do this ever since I first suspended a camera from a kite line.  But when I first asked about the possibility of doing KAP in the park, the answer was a very definite no.  I’ve been trying to teach my kids to get permission first, and not have to ask for forgiveness later, so even though it hurt at the time, I followed my own advice and remained patient.  Apparently that approach worked, because I’ve now been invited to do KAP in the park.  Not only that, but the rangers who invited me would like me to fly over the active vent in Halemaumau Crater.

Gulp!

It’s one thing to have a dream, especially one that’s been filed in the pipe dream category for so long I never thought it would happen.  It’s quite another to have an invitation, and to need to set dates and times. In the hopes of getting some feedback from someone who had done similar work, I posted all this to the KAP Forums.  The responses I got were very helpful.  Aside from the obvious safety issues, there were a couple I hadn’t thought about:

  • Because of the distance from the surface of the lava lake, heat damage isn’t likely.  Even with the kite line at zero degrees off the horizon, it’s several hundred feet down to the lava lake.  Not a problem.
  • Chemical attack is an issue, but probably not a big one.  Nylon and polyester, the two materials present in my kite sails and my kite line, are prone to attack from sulfuric and hydrochloric acid, but only at concentrated levels.  One of the folks on the KAP Forums said that the UV damage from sunlight exposure would probably outweigh the chemical damage from exposure to acid gases.  Besides, the acid gases are concentrated in the plume.  Keep the kite and line out of the plume, and all’s good.
  • The aluminum parts of the rig are anodized, and shouldn’t be prone to chemical attack.  The anodizing process uses sulfuric acid to grow the oxide layer on the aluminum, so further exposure shouldn’t cause issues.  Anodized aluminum is far more prone to chemical attack from caustics.
  • The camera electronics may be damaged from even mild acidity, so I’m planning to bag the camera.  Optical coatings may also be prone to attack, so I plan to use a sacrificial UV filter over the lens.  If it looks like the coatings are being damaged, I’ll have to re-consider my approach.  But the camera should remain unharmed.

There were other safety issues raised about the actual kite flying.  This is one area that will take some direct experimentation since there’s no way to predict what any of these will mean:

  • The Halemaumau crater is down inside the Kilauea crater.  The crater walls of the Kilauea crater are about 330′ high upwind of Halemaumau, and are about 10,000′ away from the launch site.  This presents about a 30:1 distance:height obstruction up-wind.  This is at the edge of what is acceptable for placement of meteorological equipment.  There shouldn’t be a significant wind shadow at that point, but there may be turbulence that will have to be taken into account.
  • There are two ways that heat can be transported from the lava lake into the atmosphere.  The first is convective.  The second is radiative.  Both will be present.  Convective heating should be confined to the gas plume coming out of the vent.  So long as the kite isn’t in the plume, it should be ok.  Radiative heating may cause issues even with the kite well above the plume.  One KAPer who spent time flying a KAP rig over a volcano in Vanuatu said he experienced massive thermals that fell off as the kite slid sideways away from the vent.  In the end his kite inverted and flew into the ground, despite all his efforts to get it back under control.  This must be tested before a rig is hung from the line.

And finally there are the personal safety issues to be dealt with:

  • Find out what personal protective equipment should be used (hard hat, steel toed boots, respirator, etc.)  Most of these I use regularly at work, so it will be a matter of finding out which PPEs are necessary, and under what conditions they’ll be needed.  If it’s necessary to use a respirator, I’ll need to shave.
  • Do not clip my winder onto my person at any time.  This has come up on a number of flights I’ve done that involved flying out over cliffs.  So long as there’s a cliff, don’t clip on.  Period.  With a winder in-hand, it’s always possible to let go.  With the winder clipped on, a sudden gust and an over-sized kite could drag the kite flyer off the cliff.
  • Find out how long I get before we have to head back.  This last one will determine what approaches I take, and whether I can get all the testing done up front before the photography begins.

All in all, it looks like I’ll need at least one dry-run test without a load, and then with an 860g water bottle dummy weight to match the weight of my rig.  If there are strong thermal effects, or if I can’t successfully keep the kite, line, and rig above the plume, I’ll have to pull the plug on the flight.

On a better note, the pictures themselves should be quite good.  I was concerned that the lava lake would be vanishingly small in the picture frame: a spot of orange.  But at a 40 degree angle between kite flyer and camera, the spot should be just under a thousand pixels wide.  At a 10 degree angle, it should be just under two thousand pixels wide.  Aiming will be critical, but the results should be worth it.  The lava lake should dominate the frame.

Which brings up the last point:  How to actually photograph the place?  I’m planning a couple of approaches:

  • Open with ortho autoKAP using an intervalometer set to a five second interval.  I get roughly 400-600 images per chip.  This gives me between half an hour and 45 minutes to fly a camera over the crater and get orthogonal pictures.  During this flight all my attention will be on the kite and camera, without having to worry about a remote.
  • Next do a second autoKAP flight, this time using the prototype controller a friend and I have under development.  This is where we’ve been putting the bulk of our efforts for how we like to capture a place with a camera, so it’s the best approach I could take for this part of the photography.  With the frame rates we’ve been getting, this is about a 30 minute flight before the chip fills up.
  • Finally, if time allows I’d like to do remote controlled KAP.  I would only do this if time allowed, and if the flying conditions were such that I felt comfortable splitting my attention between the remote and the kite winder.  If in doubt, this part of the program would be cut.  But this is the one I’m most looking forward to.

But in a larger sense, what I’d like to do is demonstrate KAP for the folks at the park, and show that it can provide access to vantage points that aren’t otherwise available, that it can be done safely without significant risk to personal safety or to the safety of the park itself, and that it offers the park a very real, very available method for close distance remote sensing.  In a perfect world, my follow-up to this would be to build out a set of rigs for the park rangers, and to help them get started in the world of KAP.  I think it has a lot to offer.

And I can’t wait to see how the pictures turn out!

Tom

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Kiholo Bay Inlet

Posted by Tom Benedict on 07/06/2009

Worldwide KAP Week is over for 2009, but KAP is a year-round activity for me.  The past six months we’ve been plagued with volcanic gasses coming out of the Halemaumau Crater on Kilauea, but a few days ago the tradewinds came back, blew the volcanic plume out to sea, and for the weekend, at least, our sweeping panoramic views were back.  It was a tough call whether to do ground-based photography or to fly a camera, but in the end the kites won.

Unfortunately because we’d had such uncharacteristic wind for such an uncharacteristically long time, the wind models I rely on to decide where to fly were reporting bogus information.  The models predicted 6-8 knot kona winds at my house, whereas I could look outside and clearly see it was blowing 10-12 knot tradewinds.  When technology fails, the eyeball prevails.  I packed my gear and my son and drove down to the coast.

In addition to editing the book for Worldwide KAP Week 2009 and starting work for a book of my own, I’ve also started making some KAP posters.  But in order to print them at the size I would like, I’ve been faced with the resolution limit of my photography.  I’ve been getting my posters printed using the El-Co Color Labs Internet Special.  They use a Durst Theta printer, and print on Fuji papers using Fuji chemistry.  A quick word about digital printing:  There are two basic ways to make a digital print.  One is to use a transfered medium, like a dye sublimation process, or an inkjet process.  The other is to take a photographic paper and to expose it to light.  Each has its own advantages, but I like the second for the bulk of the photo work I do.  The Durst Theta printers expose photographic paper to light, and then develop the paper the same way a film-based photo lab would.  The result truly is a photographic print.

But resolution is the key.  The Durst Theta can print at up to 254 dpi.  At 24×30″ that’s an image 6096×7620 pixels, or a 44 megapixel image.  I’ve made prints at resolutions as low as 150 dpi on a Durst Theta printer, but I prefer not to go below 200 dpi.  For this set of posters 200 dpi is my lowest resolution.  This is still a huge image, and the bulk of the pictures I have on file simply aren’t up to the task.

This has driven me to re-visit sites where I’ve been able to make good photos, but without the resolution necessary to print.  So I was overjoyed when driving down the coast to find that the wind at Kiholo Bay was a nice 7.4 knot on-shore.  Perfect.

Kiholo Bay has a fantastic reef, and is an outstanding place to do snorkeling and SCUBA.  There’s a good dirt road that will take you all the way to the water’s edge, so there’s no great hardship to get there.  It’s a popular spot, but not so overcrowded as, say, Hapuna Beach.  But if you’re willing to go a little further and work a little harder, Kiholo Bay has a feature that’s not to be found anywhere else in the Islands: the inlet at Kiholo Bay.

Wainanali`i Pond

There are two approaches to the inlet.  One is around the water’s edge from the park at Kiholo Bay.  The other is to park off the side of the highway, a little more than half a mile away.  The walk across the lava is not bad, but it’s not a traditional trail.  The “trail” is a series of paint splotches on the rocks to tell you vaguely where to go.  But the ground is rough lava.  It’s more than possible to get hurt, and this time I did.  I twisted my ankle.

A Study in Salinity

What makes the inlet special is that it’s a relatively deep patch of water with a very shallow mouth connecting it to the sea.  The level of the pond rises and falls with the tides, but tidal flow causes very little mixing of the water inside the pond.  As a result it is highly stratified, with seawater salinity levels at the surface, and high salinity levels further down.  The salinity at the bottom of the pond can easily be double that at the surface.  Select euryhaline organisms inhabit the higher salinity levels, turning the water its characteristic opaque aquamarine blue, whereas the surface water is all crystal clear.

The shallow mouth and opaque water in the inlet make it the perfect habitat for honu, or Pacific green sea turtles.  The pond is relatively free of predators, so the honu are able to forage in some measure of peace and security.

Flying Solo

The honu swim in the high salinity waters at the bottom of the pond, moving like phantoms through mist.  Every once in a while one will come to the surface for air, slipping into the clear waters above and then descending once more into the obscuring depths.

The arm of land that cuts the inlet off from the sea is mostly composed of rounded rocks rather than the hard lava flow that makes up the opposite shore.  This provides a good spot for honu to come up out of the water to rest and sun themselves.  Honu are protected by law, so people are not supposed to approach or touch them. A 20′ minimum distance is required, but I try to maintain at least 40′ between me and a honu on land.  With the low traffic of humans at the inlet, and the lack of predators, this provides a wonderful spot to study them.

A Study in Turtles

Hawaii Preparatory Academy (HPA) maintains a remote observation station at the Kiholo Bay Inlet.  The station has had some upgrades since my last visit, and now sports three PV panels, a fixed mount infrared camera, a fixed mount visible camera, a pan tilt zoom camera, and an RF link back to Waimea.  To learn more about this installation and the research program, you can visit:  HPA/NOAA Sea Turtle Research and Conservation Program.

But for me, the Kiholo Bay Inlet is simply a beautiful place that I have the privilege of being able to see and photograph.  It’s not the easiest place to get to, and there’s no fresh water or shade to speak of.  But Kiholo Bay isn’t here for us, it’s here for the honu.  I just feel fortunate I get to visit from time to time.

Idyllic

Tom

(Note:  I have been calling the Kiholo Bay Inlet by the wrong name: Wainanalii Pond.  This is how it is commonly labeled on maps, hence my mistake.  But during a conversation with Bobby Camara, he pointed out that the village of Wainanalii is a two hour canoe ride to the north of Kiholo Bay, and that it was destroyed by the same lava flow that created the inlet.)

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Mechanics of KAP

Posted by Tom Benedict on 28/05/2009

On the off-chance that my previous post sparked some interest in doing kite aerial photography, I’ll go into the mechanics of actually hanging a camera from a kite line, and convincing it to do what the photographer wants.  The approach used can be anything from quite simple to otherworldly complex.  A lot depends on what the photographer actually needs, but even more depends on what the photographer is convinced they want.  It’s important to keep these two ideas separate when you look at hanging a camera from a kite line.

Lightweight Rig - Ready to Fly

By far the simplest KAP rig I use is one I designed spedifically for doing mapping.  It was built for one specific trip, but it’s such a versatile rig I’ve used it numerous times since.  The requierments of the trip drove the design:  For starters, there is very little wind at the site, so lifting a heavy KAP rig was out of the question.  The bulk of the weight in this rig is the camera itself.  The rig’s weight is almost negligible.  For the purpose of mapping, all the pictures needed to be as orthogonal as possible, so there is no provision to tilt or pan the camera.  And we would need to take pictures over the course of several hours with no opportunities to change batteries during the flight, so battery life was of paramount importance.

There is no provision for the photographer to tell the camera when to take a picture.  Instead the camera is running CHDK, a toolkit that runs on top of the camera’s native firmware.  In this case CHDK was running an intervalometer script that let the camera take pictures every five seconds without any user intervention.  No mechanical linkages, no servos, no fancy electronics, just the camera itself running a pre-canned program.

Lightweight Rig Airborne

In the end the rig performed marvellously.  Complete with camera and the four AA batteries the camera requires, the rig came in just over 450g.  It flew on one set of batteries for two straight days, and took more than 2,000 photographs.  The photos from that trip are being used to map an archaeological site, and will be used in papers that should be published in the next year or so.

Current Rig - Late 2008

At the other extreme is my radio controlled KAP rig.  It’s built almost entirely out of off-the-shelf parts from Brooxes, the main supplier of commercial KAP equipment. The rig allows the photographer to pan and tilt the camera, and to operate the shutter.  Brooxes sells other components that would allow the camera to rotate from horizontal to vertical, and other accessories exist that allow the photographer additional control over the camera itself.

The rig started off as a Brooxes BBKK, but over the course of a few years I added a carbon fiber leg kit, gear reduction for the pan axis, a set of PeKaBe blocks for the suspension, and a number of other improvements.  Two changes have been made since this photograph was taken:  The first was to replace the aging 72MHz AM radio with a 2.4GHz Turborix.  The second was to remove the shutter servo and replace it with a GentLED-CHDK.  Unfortunately I haven’t photographed this rig since the changes were made.

The GentLED-CHDK is one of the cooler pieces of hardware I’ve bought for my rig.  It is a smart cable that plugs into the RC receiver on one end, and the camera’s USB port on the other.  When the photographer flips the shutter control on the RC transmitter (in my case I set it up as a switch rather than a joystick), the GentLED-CHDK sends +5V down the USB cable to the camera.  One of the features of CHDK is that you can monitor the +5V line on the USB port and take action when the camera sees it.  In my case I run a script on my camera that says as long as +5V is being applied, behave as if the shutter button is being held down.  In single-shot mode, this means each time I flip the switch the camera will take a picture.  In continuous shutter mode this means that I can hold down the switch on the transmitter and the camera will keep taking pictures as fast as it can, roughly every 1.1 second.

The two rigs are as different as they could be and still get the job done.  One was the product of a few hours of thinking and about an hour’s worth of time in the shop.  Total expenditure was maybe $50 for the Picavet suspension, most of that being the PeKaBe blocks.  The bulk of the rig came out of the scrap box.  The other was the product of a few years of tinkering with a commercial rig.  Total expenditure is probably several hundred dollars by now, but still probably less than a good carbon fiber tripod and professional ball head.

What is important to take away from this is that there is no one right way to hang a camera from a kite line.  And depending on what you actually need, an extremely simple rig like the ortho mapping rig may get the job done just as well as a more complicated, heavier rig like the BBKK.  Before becoming discouraged at the prospect of designing and building a rig from scratch, consider the commercial options.  And before becoming discouraged by the cost of the commercial kits, consider the possibility of simplifying your requirements and making one yourself.

It’s possible for anyone to do aerial photography.  If you want to do it, do it.

— Tom

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