Just as it is obviously important to balance a jib arm, it is equally important to balance one's fluid head, especially if you are putting it on a jib arm. Unfortunately, I have found over the years that it is not uncommon for people not to know how to balance their fluid heads. When they are only working on a tripod, they can get by with it not being properly set-up, but when it's on a jib, an improperly set-up fluid head can inhibit the jib's movement considerably. You will find yourself booming the jib when all you wanted to do was tilt the camera. So if you are having trouble hitting your marks with the jib, before you blame the jib, or yourself, have a look at your fluid head.
I worked in a camera rental facility for many years and it was common to watch camera assistants simply muscle the head around a bit, dial in some fluid drag that felt appropriate, and think, "Yeh, that's good." They did not do any balancing at all, and that really is not the correct way to do it.
Almost all fluid heads have locks for the pan and tilt, fluid drag adjustment for pan and tilt, and usually an adjustment for the spring tension on the tilt. The better heads have a continuously adjustable spring adjustment which is ideal for accurately dialing in the balance. Others have a lever (or levers) to either engage or disengage a spring (or springs). Unfortunately, the really low-end heads often do not offer a spring adjustment. For those of you who have an adjustable spring, here is what I recommend:
1) Put the camera on the head and lock the tilt axis.
2) Set the fluid drag setting to zero, so that when you unlock it, you will only have the spring affecting the tilt.
3) Unlock the tilt axis and balance the camera fore and aft on its sliding balance plate. We haven't adjusted the spring yet, so it will probably want to fall either backward or forward, but it should have the same response in either direction. In other words it should be centered so that it is neither front nor back heavy. You can fine tune the fore/aft position once the spring is set properly.
4) Now set the spring tension. Heads like those made by O'Connor or Cartoni generally have continuously adjustable springs so you can dial in the tension accurately. Others like Sachtler have preset spring choices that allow you to either engage or disengage various springs and these will get you very close. Either way, you now want to set the spring. To do this, tilt the camera forward about 45 degrees to see what it does as you begin to let go of the panbar. If the camera wants to continue falling downward, then you need more spring tension. If it pulls upward when you let go, then you need less spring tension. Dial in, or manipulate the on-off levers, to find the right tension.
5) If the camera is balanced fore and aft properly, and the spring tension is set properly, the camera should always stop exactly where you point it as you let go of the pan bar.
6) Now dial in the desired amount of fluid resistance for the tilt and the pan.
7) And this brings me back to my original point--that is, for a jib arm, this will be using very minimal fluid drag. You want a floating feel to the movement of the head just like the floating feel of the jib arm itself. As I said above, you do not want the jib to boom when all you want to do is tilt the camera, which is what will happen if the drag is too strong. On a tripod, you may prefer more resistance, but on a jib you want a light, floating feel.
Please take the extra few minutes to properly balance both the head and the jib. It will make your work much more satisfying. For those of you unfamiliar with our Vector Balancing System, please read those instructions as well.