Merlin Question...balance....

[Tom McDougal]

Hello all...I have a question about left/right trimming.

My merlin finally came in. Working great but I don' tthink i'm in balance.

I seem to get in balance for a second while holding the rig straight, but once i start moving, the camera will lean left. I counter it and adjust it but then it will do the opposite. Anyway to correct this? This is with a GL2 camara with similar specs as the cookbook but with 1 finish and 1 regular weight on the front.

I guess my question is, if i rotate the camera around (panning), should the camera remain balanced?


Thanks......

[Mikko Wilson]

Tom,
First off, congrats on your Merlin!

If you hold the rig still and balance it, you should be able to pan 180*, stop it, and it should remain prety much balanced.
There is a *tiny* amount of slop in the gimble - if it was 100% tight it of course would be locked up an not move!


If the camera tilts *while* you are panning, that means that the rig is not in "Dynamic Balance".
If it's balanced statically (hangs level) but not in dynamic, the solution is to open teh dovetail lockign lever to teh middle position an slide yrou camera a little way in one direction. Then use the fore-aft trim roller to move the gimble to return the camera to level. A quick pan to see the result, if it improved, repeat untill good, if it made it worse, repeat, but go the other way! (this guess and check system is the fastest way to do it.)


If that sounds too complicated, I can also walk you through step by step.

The first question is: What is your drop time?

- Mikko

[Tom McDougal]

Thanks. Merlin is great so far. We did the research and choose this over glidecam. Not that i've tried the glidecam 2000, this is a nice product.

Drop time is pretty much 1 second.

I took a break after playing with it for serveral hours yesterday. I didn't know it was that much weight on your hands and wrist.

Doesn't the dovetail plate deal with horzontial tilt....?
more of problem is the vertical tilt. every i correct it, use the rig, it seems to be off and i kinda have to hand the rig in a certain place to make the bubble level.


Prehaps its not so much the balanceing and more with my hand positioning and trying to pan/ or tilt camera. I think i will be spending alot of time practiing hand positions as its not cormfortable for me.

[Mikko Wilson]

Hmm.. I'm a little confused by what you mean by vertical and horizontal tilt?

There's a lot of diferent terminology used to describe all teh movement possible with Steadicam. Either comon camera language, or aviation terms can be used.

The first set of movements are the ones where you rotate the rig & camera on the gimble:
> Pan - same as on a tripod, "looking" (turning) the camera side to side. ['Yaw' in aviation]
> Tilt - again, same as tripod, "looking" up and down with the camera. ['Pitch']
> Roll - same as "dutch tilt", this is rolling the camera on it's side. ['Roll'] This effects the "Horizon" in the image, and is normally prefered to be flat and level.

"moving the camera" refers to actually moving it throguh space, not rotating it on the gimble. Movements are:
> Up/down "Booming".
> Left/right (AKA: "Trucking" or "Tracking").
> Front/back or in/out (AKA: "Dollying").

There's a few terms specific to balancing too:
> Fore/Aft balance - moving someing forward or back on the rig to make the camera tilt up or down. "Front heavy" will cause a Tilt down.
> Side/Side (or Left/right) balance, causes the camera to roll. If you move the camera sideways to the right on the stage it'll roll to the right.
> Vertical balance is the balance of weight above and below the gimble. This is tested with the "drop test" and described by the "drop time". If a rig is too "bottom heavy" it'll swing like a pendulum, if it's neautral it will stay at any angle you leave it, and if it's "top heavy" it'll try to flip upside down (to make itself 'bottom heavy' by inversion.) Normally you want the rig just slightly bottom heavy, so it hangs base down but doesn't pendulum much.

There's 2 types of balance:
> Static Balance ("Static") is when the rig hangs level when it's not panning (normall not moving at all). If you just hold the Merlin and it hangs base down with the camera level both fore/aft (tilt) and side/side (roll) then it's in static balance.
> Dynamic balance ("DB") is a little more complicated and due to the way stuff is spread sround teh pan axis. In short: If you are in Static balance, and you pan the rig and it spins flat, it is in Dynamic Balance too. If howeverwhen you pan, the rig wants to tilt either up or down, then it's not in dynamic balance. The solution is the move the sled slightly forwards or backwards in relation to the gimble. This will then call for slight repositiong of some other part to keep it in static balance too.

Whew, I think that's most of them.

----

An "ideal" Merlin is slightly bottom heavy, with a drop time of about or just over a second. It iwll want to return to vertical by iself, but it won't swing around like a pendulum when you move. When you hold it without moving by just the handle it should hang flat and level, and it should remain flat and level when panning.

- The number and placement of wights, the size of the caliper arc, and the "Z" adjustment at the gimbel all adjust vertical balance.
- The choice of mounting hole (A - O) helps center the camera on the dovetail plate.
- Sliding the dovetail plate (and attached camera) a a rough adjustment of fore/aft balance that affacts the tilt angle of the camera (you normally want it flat). This is also what you use to bring the rig back into static balance when adjusting for Dynamic balance.
- The fore aft trim roller (on the side of the stage) fine tunes the fore aft balance roughly set by the dovetail position. This adjustment is also used in conjuntion with (and moving opositly) to teh dovetil to set dynamic balance.
- The side/side roller (under the stage) is used to adjust side to side balance, so that the camera doesn't roll and has a level Horizon. This is checked by the bubble level on the back of the stage.

Once the Merlin is balanced properly, it then comes down to practice to perfect oprating.


Ok, *that* was a long post.

- Mikko

[Tom McDougal]

Sorry for using wrong terminolgy. I think i understand what your trying to say. I think it comes down to practice now. I'll let you know if I have any other questions. Today I will be shooting some footage and probally post something tomorrow.