This is the second in a multi-part series about Will's Third-Person Live-View Camera rig project. Here's the first part.
We're three weeks out from MakerFaire, and my third-person camera project is coming along nicely. After some initial tests, I'm pretty sure I have all the electronics stuff figured out. The GoPro HD Hero 2 handles live feed out of its HDMI port like a champ, and the Sony head-mounted display seems like it will work just fine. Yes, it's somewhat heavy, but it gives me a good high-resolution display to test with.
I hooked everything up for the first time this morning, using my wife as a temporary camera mount, and an extension cord to power the Sony goggles as I walked around my backyard. Watch the video, and then we'll talk about what I've learned so far.
First, there are three important things for camera placement--the height, the distance from the back of my head, and the angle of the camera. I can keep it really close to my head, if I aim almost straight down. Unfortunately, that means I really can't see in front of myself. It seems like the sweet spot is between 3-5 feet behind me, with the camera aimed 10-15 degrees down. Because the GoPro uses a wide-angle lens (170, 127, or 90°), I get a good field of view. Last week, several folks suggested offsetting the camera so it's just over one shoulder, and I'm going to try that too.
Second, it's very important that you be able to see your feet while you're walking. The close shoulder tests we tried didn't work well.
I was worried that the live feed from the camera would lag slightly, due to post-processing, image stabilization, or whatever. This was a concern with Contour's helmet cam, which is why I chose to test with the GoPro. Luckily, that didn't seem to be the case at all with this camera.
Mounting the camera is going to be trickier than I anticipated. All the mounting equipment for GoPros depends on you using the polycarbonate shell. Unfortunately, the shell blocks the HDMI port on the side of the camera. There are two ways I can fix this, either make a hole in the shell to accomodate the HDMI cable or rig up another mount that won't require the shell. I'm going to test print a mount I found on Thingiverse and see if I can use that with some rubber bands, but if that doesn't work out, I'm comfortable Dremeling the Go-Pro's shell.
Adapting to the camera and display was surprisingly easy. Maybe I can thank years of playing third-person video games for that, but my wife picked it up pretty quickly, and she doesn't play many games.
Next steps are figuring out the frame and power. After reading a bunch of comments from last week, I think I'm going to try bike parts and aluminum tubes to attach the camera to the frame. I'm thinking that I can mount a tube low on a backpack frame, and secure it to the upper corners of the frame using guy wires. That should be light, while remaining relatively stable. I'll also be able to make adjustments relatively easily, which wouldn't be possible if I was using a completely rigid design.
The last step is to figure out power--the Sony goggles rely on 120V AC. The goggles seem to draw at most 15W, so 20-30Whr battery would be good enough for an hour or two of use, minus whatever power we lose to the inverter. I can get a lead-acid battery with an integrated inverter at Best Buy--your PC's uninterruptible power supply is exactly that--but it's going to be really heavy.
Alternately, If I wanted to go all day, I could spend a few bucks more and get a backpacker's kit that includes 50Whr battery and solar cells that should help keep the battery topped off. It's a lot more expensive, but I should be able to run all day with it, and it weighs about a quarter as much as a similar capacity lead-acid battery. If I'm going to wear this around MakerFaire all day, I'll notice that extra 20 pounds by the end of the day.
If you have ideas about power or the physical harness rig, post in the comments. The first round of suggestions was very helpful!