Focus failed totally on aerial shoot with Z1

[Chris Hewitt]

Managed to get up in the air this morning. Vibration wasn't too much of an issue this time (same aircraft) but the Z1 is soooo sensitive....saw it in a few frames but generally ok handheld. Useable footage, however, we had a very bumpy ride, clear skies, great weather but turbulent.
As it always happens, it occured to me afterwards that maybe a couple of bungee ropes suspended from above the side window with camera resting inside the loops might have been the best way to go, these would hopefully absorb all the vibration as well as bumps and arm fatigue.
Worth a try and an idea that can be practiced on the ground.Thanks everyone for your input, that's what makes this forum so good!

[Bob Hart]

Some news crews use the bungees in a Jetranger helicopter but their cameras are much heavier which means lots of resistive mass and dampening effect.

A home-made stabiliser I made for small cams in confined spaces, worked after a fashion but was pretty much uncontrollable for pan and tilt moments at full zoom-in, smooth until one tried to do active follows.

The stabiliser structure also added axtra mass to the camera which I found helpful. I found that letting my arms float somewhat helped when hitting the lumps in the air although the visible aircraft interior can be then seen moving around the frame of the shot. This effect can be seen in the over-water formation turn about midway through this clip.

http://www.youtube.com/watch?v=cdMgDdks8MY

For a small cam, a divebelt weight would be about right. I have previously suggested drilling a hole through one and using a longer tripod screw to fasten one to the base of a small camcorder.

However in light of a very recent report here of structural failure within a camcorder's main internal frame, I have revised my ideas on how to fasten the weight in favour of full wraps of gaffer tape where it can be applied without impeding the camera controls.

As for there being less vibration this time round in the same aircraft, one reason may have been a slightly richer mixture setting which tends to smooth out the engine power pulses a little although it does not help with prop buffet. The pilot may have been following his normal mixure settings but if the air was warmer (higher density altitude) the engine may have been running a little richer.

If the mixture becomes over-rich, in a 172 with a six cylinder engine, you may encounter a barely noticeable swing in engine rpm with a period of about 4Hz which might not be helpful for your images either.

Do not take too much notice of my comments as I tend to rave on with lots of theory and less provable fact.

[Tim Ribich]

Originally Posted by Bob Hart

Do not take too much notice of my comments as I tend to rave on with lots of theory and less provable fact.

Bob,

Having experimented with shooting video from experimental/sport planes and 172s-- using everything from remote control stut mounts to handheld-- your comments and insights on the subject are most interesting.

Do you have any images of the rig you used for the YouTube footage?

If you ever need a volunteer to test any of your theories, I'd be more than happy to do so.

Tim

[Bob Hart]

Tim.


This is the stabiliser.


YouTube - STABILISER


As it presently exists it is a dead-end. It needs gyros to become controllable and an antifriction bearing on the post as with a real steadycam. I have not yet built the gyros. They will be powered by small scale aircraft electric motors and will be of about the same mass as those from a directional gyro instrument.

The pan and tilt control is via what I call tiller loops, which are those wire things coming off the side of the camera mount plate.

Tilt and roll are fairly contollable but a bounce develops which is operator induced. You will observe the pan motion is jerky. This is due to the lack of an antifriction bearing as I have tended to attempt pan corrections by rotating the hand grip, which is the gray plastic cylinder.

I also operate the stabiliser one-handed, using thumb pressure alone on the tiller loop to control movements and the right hand intermittently when things start to bounce. The tiller loop was pinned by the thumb against the hand grip, then slid vertically or horizontally for the adjustments one an equilibrium position was found.

I set the countermass to leave a little pendulum effect. Too much and the motions of the aircraft start to take over.

The gyros are not intended to actually stabilise the cam but to offer resistance to the operator inputs and thus dampen them.

OIS was set to "on" for the C152 shot in the formations clip. It is helpful until you try to do follows when zoomed right in. You will see the jerkyness in the C152 shot in the movements when I was attempting to move the shot over the aircraft.

[Greg Laves]

Here is a company that makes gyro stabilizers for this type of application. I have a KS-6 and it works really well. The only problem I have with it is the pilot that I usually fly with. He thinks his helicopter is a airborn sports car. He very often exceeds the turning rate that the gyro will tolerate. Really not good on the gyro. I have rented my gyro to a shooter using an HPX500 Pana and he thought it worked great even though his camera's weight is more than is recommended for the KS-6.

Kenyon Laboratories--Kenyon Gyro Stabilizers for cinematography, cameras and binoculars.

[Giroud Francois]

possibly it could come that you are pointing the camera down and there is some part loose in the optical stabilizer of focus mechanic. so each bump is moving all the assembly and it goes back in place with gravity.

[Vincent Oliver]

Just been watching the last episode of "Britain from Above" (BBC) and they had the same trouble, all the inside shots of the Andrew Marr (presenter) suffered from dreadful vibration. I am surprised the BBC passed this for transmission. YOu should be able to catch this show on BBC iPLAYER BBC iPlayer - Britain from Above: Untamed Britain only available for seven days from 25 Aug 2008

[Bob Hart]

I am aware of the Kenlabs products. There is a KS4 at Camera Electronics, a local independent film and digital stills equipment vendor who rents it out to clients here in Western Australia.

The KS6 is rather expensive to land here for the little bit of work I would have for it.