Thursday, October 10, 2013

Fixing Jello Problems with the Phantom Quadcopter

I continue to be amazed, and charmed by the Phantom Quadcopter. I still can’t get over how easy it is to fly, and I say that despite having already had one close encounter of the tree variety(!) It’s amazingly easy to control. Even with only 20 minutes of flight time under my belt, I can get it to go where I want it too…mostly, and as long as I allow myself some space to make up for those times I go left instead of right, I’m pretty confident about flying it. That’s the good news.

The bad news; you can get a fair amount of jello in your video due to vibration from the aircraft transferring to the camera. I’m flying a Sony HDR-AS15, but people flying the GoPro have reported the same results.

So how do you remove it; or negate it?

There seems to be two major solutions offered by the gurus of the web, though I’ve recently come across a third possible “jello-fixer,” so I’ll cover that last.

Anti-vibration mount
There’s at least two carbon fiber mounts being sold for reducing jello. I’m not sure that it’s the carbon fiber that’s doing the trick; I think it’s the rubber grommets between the two pieces of carbon fiber that are doing all the heavy lifting (or dampening.)

I’ve also seen one YouTube video where the flyer suggested using silicon dampening material between the mount and the air frame (see below).

I’ve ordered an anti-jello kit because I think it’s the thing most likely to have the biggest effect (though I have no proof of this statement.)

In the meantime, I did try using some rubber sheeting about 1/8 thick to isolate the camera from the frame, and I actually think it did reduce the jello effect noticeably. On two flights without the rubber I saw noticeable jello, but on two using the rubber sheeting, if the jello effect was in evidence, at least it wasn’t glaring.

Using a piece of rubber between the camera and the mount to reduce vibration. Note that Duct Tape (not shown) is then judiciously applied to keep the camera (and rubber) attached to the frame!

But I’m waiting for an anti-jello kit.[DJI Phantom GoPro Anti Vibration Anti-Jello Vibration Isolator Low Profile Carbon Fiber Mount $16.99]

This video shows the effect, prop balancing and one method for dampening using a silicon-based material.

If you have the money to spend, you could also go with a brushless mount. DJI even sells one just for the Phantom, but it's expensive and hasn't gotten great reviews. At least on Amazon.

The next theory of vibration reduction is “balancing the props.” This one I’m not so sure about. I can understand the idea behind the theory; having a propeller that’s heavier on one side causes instability. But these are molded, plastic propellers that I don’t think are going to be significantly out of balance.

Furthermore, if you argue “sure it’s small, but these are small props so small differences can have big effects”, well sure, BUT, the solution for balancing them involves sanding material off the propeller, or adding plastic strips to the propellers i.e. changing their shape. If you can convince me that changing the weight of the propeller in a small way will change the propellers operation, then surely changing the shape of the propeller could similarly effect things?

So I guess I’m not convinced. Also, unfortunately, of the two or three videos I've watched so far, everyone prop-balanced their copter also added some isolation method; so was the prop-balancing really a factor?

That said, I have ordered a prop-balancer [JMT Carbon Fiber Magnetic Propeller Balancer] because it was under $10, and I thought I’d give it a try. Just being able to tell people that I bought a “Prop Balancer” is worth the price!

Here's a good video on balancing: The prop balancer shown, I think, is this one

Final Theory – lowering the shutter speed
The last suggestion for improving performance is lowering the shutter speed. Place an ND filter in front of the camera and lower the shutter speed. I can see how that would create a more blurred image; I’m just not sure how it reduces the jello effect. It may mask it, rather than fix it.

One other problem; you don’t have the ability on these cameras to set the shutter speed manually, so you don’t really know what shutter speed and ISO you’re going to end up with.

I’m holding off on this one for the moment, though it might be useful to change the image by adjusting the exposure.

GoPro DJI Phantom Quadcopter-Reducing the Jello Effect | Polar Pro

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