In the previous video I posted on a Black Magic Pocket Cinema Camera 4K rig mounted on a DJI RS 2, I showed that I had some issues with vibrations. In one of the comments, Australian Image said “the camera is so badly arranged that you are going to get vibrations no matter what”. And he was right. All those loose cables and especially that focus gear, which I should have cut, were probably moving around when I walked. These movements caused changes in the centre of gravity of the rig mounted on the gimbal.
If the centre of gravity moves around it will statically unbalance the gimbal, meaning that motors will struggle and the gimbal will vibrate.
To see this you just need to move a cable from one position to another position. You just need a tiny change to statically unbalance the gimbal.
Another thing Australian image mentioned is dynamic unbalance. Dynamic unbalance is the result of a non-symmetrical mass distribution, which can be quantified with the Product of Inertia or POI. The POI is equal to the product between extra mass, radial offset from the centreline, axial offset from the centre of gravity, and two. Take this cylinder for example, the centre of gravity is in the middle. There are no extra weights so POI is zero. If we spin the cylinder about its vertical axis, it will spin without problems, without vibrations. If I add two equal masses in this way the centre of gravity won’t change and the cylinder is still statically balanced. Now POI is non zero. If we spin the cylinder about the vertical axis, centrifugal forces will act through the two weights to produce a couple. So basically the spinning cylinder will wobble and vibrate.
This is something you can test on a glide cam, but on a gimbal it’s much more difficult. So as a rule of thumb what you can do to reduce dynamic unbalance is to minimize the product of inertia. You can do that by bringing the extra masses, which in this case are the power bank and the CFAST card adapter, closer to the centre of mass of the camera.
So, in summary make sure cables don’t move around when you move the gimbal to keep static balance and make sure accessories are as close as possible to the camera.
With this configuration I got less vibrations than what I had before. As you can see in the following tests some vibrations are still there.
This is what I got with the standard mode. I was active tracking this target.
This is what I got after turning supersmooth on.
Here I changed lens. I replaced the 45mm lens with a 16mm lens.
I tried selfie mode, but walking with 3.5Kg on an extended arm is really heavy.