Momentum of GG following Pan

Rob Evans · May 20th, 2008, 03:05 PM

Hi,
Had my extreme a couple of weeks now and am mightily impressed with it. But i have noticed a couple of times an odd thing occuring. At the end of a fast pan, or a relatively quick movement, it appears that the GG has some momentum that causes it to jump a little bit. Having had a look at the mechanism earlier I can see how this can happen, as the GG itself is mounted on 3 legs with elastic properties, but I just wonder if anyone else has noticed it - is it normal?

Thanks,

Rob

Bob Hart · May 20th, 2008, 09:12 PM

Choice of two possible causes.

There is likely enough rotational movement in the groundglass motion to induce some centrifugal forces which would resist a panning motion enough to cause a hiccup the moment you stop the pan movement.

The sudden stop of the pan movement might be enough to cause the groundglass carrier to move a little furthur, or slow momentarily depending on whether the stop is additive or subtractive to the direction the groundglass carrier is going at the time.

My personal choice is the first suggested cause because a panning movement is an angular deviation more likely to be resisted by a centrifugal force. Maybe some interaction between first and second causes.

A test using a pure lateral tracking movement would tell the truth.

I would not fret too much over it. Nothing is likely to break before the camera itself does with sensible camera moves.

I have a large glass disk in a home-made which chatters off focus for about a quarter-second if I stop a whip pan suddenly. Like the Letus groundglass carrier, my disk motor is supported on compliant mounting.

Barry Green · May 21st, 2008, 03:35 PM

Do you have your image stabilization on? You should turn that off whenever using an adapter.

Bob Hart · May 21st, 2008, 04:37 PM

Barry.

Thank you for pointing that one out and saving the enquirer from a possible dead-end answer. I had forgotten about stabilisation which I always select off.

Rob Evans · May 22nd, 2008, 01:34 AM

Thanks guys, I *think* the steadyshot function is still switched on, so that could very well explain it (in which case I will hang my head and take the walk of shame!) I'll try tonight and report back....
This style of shooting is a whole new world for me, and I ruined a load of nice footage a week ago by not stopping down enough on the camera so the grain was really visibile, but usually the answers are somewhere on this board... Thanks!!

Rob Evans · May 22nd, 2008, 11:39 AM

Yep, that was it - nail on the head, bullseye, eureka! etc etc. LOL!

Thanks - most appreciated.....

Bob Hart · May 22nd, 2008, 05:13 PM

In light of the solution found to the problem, my comment above should be ignored.

May 20th, 2008, 03:05 PM	#1
Rob Evans Major Player Join Date: Apr 2007 Location: Berkshire, UK Posts: 390	Momentum of GG following Pan - normal?? Hi, Had my extreme a couple of weeks now and am mightily impressed with it. But i have noticed a couple of times an odd thing occuring. At the end of a fast pan, or a relatively quick movement, it appears that the GG has some momentum that causes it to jump a little bit. Having had a look at the mechanism earlier I can see how this can happen, as the GG itself is mounted on 3 legs with elastic properties, but I just wonder if anyone else has noticed it - is it normal? Thanks, Rob

May 20th, 2008, 09:12 PM	#2
Bob Hart Inner Circle Join Date: Dec 2003 Location: PERTH. W.A. AUSTRALIA. Posts: 4,476	Choice of two possible causes. There is likely enough rotational movement in the groundglass motion to induce some centrifugal forces which would resist a panning motion enough to cause a hiccup the moment you stop the pan movement. The sudden stop of the pan movement might be enough to cause the groundglass carrier to move a little furthur, or slow momentarily depending on whether the stop is additive or subtractive to the direction the groundglass carrier is going at the time. My personal choice is the first suggested cause because a panning movement is an angular deviation more likely to be resisted by a centrifugal force. Maybe some interaction between first and second causes. A test using a pure lateral tracking movement would tell the truth. I would not fret too much over it. Nothing is likely to break before the camera itself does with sensible camera moves. I have a large glass disk in a home-made which chatters off focus for about a quarter-second if I stop a whip pan suddenly. Like the Letus groundglass carrier, my disk motor is supported on compliant mounting. Last edited by Bob Hart; May 20th, 2008 at 09:14 PM. Reason: error

May 22nd, 2008, 05:13 PM	#7
Bob Hart Inner Circle Join Date: Dec 2003 Location: PERTH. W.A. AUSTRALIA. Posts: 4,476	IGNORE MY POST ABOVE May 20th, 2008, 09:12 PM In light of the solution found to the problem, my comment above should be ignored.

May 21st, 2008, 03:35 PM	#3
Barry Green Barry Wan Kenobi Join Date: Jul 2003 Location: North Carolina Posts: 3,863	Do you have your image stabilization on? You should turn that off whenever using an adapter.

May 21st, 2008, 04:37 PM	#4
Bob Hart Inner Circle Join Date: Dec 2003 Location: PERTH. W.A. AUSTRALIA. Posts: 4,476	Barry. Thank you for pointing that one out and saving the enquirer from a possible dead-end answer. I had forgotten about stabilisation which I always select off.

May 22nd, 2008, 01:34 AM	#5
Rob Evans Major Player Join Date: Apr 2007 Location: Berkshire, UK Posts: 390	Thanks guys, I think the steadyshot function is still switched on, so that could very well explain it (in which case I will hang my head and take the walk of shame!) I'll try tonight and report back.... This style of shooting is a whole new world for me, and I ruined a load of nice footage a week ago by not stopping down enough on the camera so the grain was really visibile, but usually the answers are somewhere on this board... Thanks!!

May 22nd, 2008, 11:39 AM	#6
Rob Evans Major Player Join Date: Apr 2007 Location: Berkshire, UK Posts: 390	Yep, that was it - nail on the head, bullseye, eureka! etc etc. LOL! Thanks - most appreciated.....