The View Up Here

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

More on the Panoramic KAP Rig

Posted by Tom Benedict on 30/12/2012

After over a week of waiting, I finally got the wind to try my panoramic KAP rig with the Canon T2i. In short, I’m torn…

On the face of it, it worked ok. Here’s a two shot sample:

Anaehoomalu Bay 2012-12-30

But digging deeper, it leaves a good bit to be desired. The same day I made this, I also set the camera up to make movies and flew it while the rig panned around. It answered a couple of questions I had from going through the images. Here’s what I really learned:

The magnetic encoder on the pan axis really does work. But the kit lens on the T2i is soft at its widest setting if 18mm, so I habitually run it at 24mm. That’s just a little too narrow to work with the shot spacing I built into the pan gear (12 magnets = 12 shots per rotation). I either need a wider lens, or more shots per rev.

More shots per rev means a slower overall rotation, so the wider lens really is the right way to go. I just can’t afford the glass right now. It’s cheaper for me to pick up a new pan gear from Robot Zone, drill out a tighter pattern of holes, and make a finer pitched rig. It would be even cheaper if I just re-programmed the controller to stop twice per magnet – once on magnetic maximum, and once at magnetic minimum. Voila, double the shot density for no actual increase in price. Can’t beat it. So that’s next.

The other thing I learned is that most of the variation in orientation, shot-to-shot, comes from random movement of the rig in the air and not from variations in the pan axis. There’s a lot of roll and pitch, but there’s also a fair bit of wind-induced yaw. Something on the KAP rig is acting like a sail. In some orientations the wind tries to blow it a little further around, and in others it tries to blow it back. After staring at the video for a while I figured it out. It’s my lens! The lens on my camera is poking way out in space, just itching to be blown around by the wind. ARGH!

There’s a fix for the wind-induced yaw as well: replace my Picavet suspension with a very tightly constrained pendulum. Since I’ve been itching to build a damped pendulum suspension, this just adds fuel to that project. If I’m careful with the design, I should be able to take out the shakes in pitch and yaw, and damp both as well. Time will tell if that’s the right way to go. Meanwhile, back to the drawing board. Literally.

– Tom

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2 Responses to “More on the Panoramic KAP Rig”

  1. Video…of course. That’s what I need to show why my shots are all badly tilted. Thanks

  2. rohan said

    Its very nice to see the article like this ,nice post.thanks for sharing with us.

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