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Old July 25th, 2009, 10:10 PM   #1
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Merlin Steadicam and ball bearings

For well over a year, I have been trying to chase down an unexplicable video hiccup when using my Merlin Steadicam with an XHAI. Video segments would be afflicted with an inexplicable flutter, shudder or flicker. It is hard to explain but you can see the problem in these videos of rooms:

Manchester Vermont Restaurant- Casual & Fine Dining Reluctant Panther Inn & Restaurant
Manchester, Vermont Video - Inn at Ormsby Hill

None of this occurred with the camcorder when used with a monopod, a tripod or a fig rig. But despite this, I sent my camcorder back to Canon and they replaced the entire lens assembly and charged me accordingly. But still the problem persisted. Today, a Canon representative sent me an email with the following:

The fact that the you are not seeing it with a tripod, monopod, nor a
Fig Rig, but only with the Steadicam Merlin makes it hard for me to find
a problem in the camera. The Steadicam Merlin uses a 6 ball-bearing
gimbal system to keep things smooth. If any one of those ball-bearings
were the least bit off, it would not be noticeable while recording, but
would show up as a stutter as panning was being reviewed in
post-production. The fact that turning OFF Instant AF seems to improve
the situation, only seems to indicate the same. In Instant AF, any
quick change (e.g. caused by the gimbal not quite perfectly smooth) in
the view will cause an instant change in the focus which would be more
noticeable than if the regular AF were to work at it’s own pace.



I am wondering if others have experienced this and whether this could be correct?

Tim
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Old July 26th, 2009, 08:20 AM   #2
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Interesting issue, Tim.

There must have been something wrong with your lens assembly if Canon replaced it, no? What was the diagnosed issue?

In looking at your footage, I can see the judder you describe which seems to be associated with your footsteps (I don't see it in shots where you were static and the rig was in motion, i.e. booming up from the bathtub). Are you using the g-platz screw underneath the lens, and ensuring that the camera is secured to the Merlin as tightly as possible so that there is no potential play or vibration possible at the mount? This could result in this type of vertical judder.

It is always potentially possible that you have a problem with your gimbal--you could always order a replacement (about $160) and if that doesn't improve things, you can return it. If your Merlin is still under warranty, you would be able to make a case for this being covered under same.

I would do a test where you walk very softly and carefully in place, then tread heavier and heavier and see if the problem magnifies or remains constant from the beginning. It would be helpful to see a video of you operating the rig to evaluate your form also. Outside of the vibration issue, I would suggest based on this footage that you may be "overcontrolling" the rig by applying too much force with your operating hand , which is causing the rolling horizons.
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Old July 26th, 2009, 08:36 AM   #3
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Thanks for your comments. Is there any way of knowing if the gimbal assembly is working correctly, just by feel or look?

How could a misaligned ball bearing cause such a video problem without me feeling or hearing it?


The problem has occurred even when I have only one hand holding the Merlin and no second hand control, but I will practice again on some flowers and see how it goes.

I returned the camera twice to Canon. The first time, they just made some adjustments but didn't tell me what. The second time they just said there was a problem with the auto focusing and it was intermittent.
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Old July 26th, 2009, 08:55 AM   #4
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I would recommend zooming your camera in to a telephoto position, standing in place and performing the "stomp test", where you stomp one foot (I would recommend the same side as the arm you use to hold up the rig) and seeing if you can detect jitter in the viewfinder. The telephoto setting will magnify the apparent effect. If there is any potential concern about the AF circuit, turn off AF completely and see if that has any effect one way or another.

If there was indeed a subtle issue with the gimbal, it could cause a problem without being easily identifiable via inspection when the rig is not under load. Certainly it would be unlikely to make a noise or transmit a sensation through the system for you to feel.

Again I would recommend looking very carefully over the method of mounting the camera to the stage to ensure that there is no possible play, and that the g-platz is providing enough support for the lens.

Regarding the operating hand concerns, as I indicated this is outside of the vibration issue but more of a comment on the overall results you are getting with the Merlin.
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Old July 26th, 2009, 09:10 AM   #5
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What is the function of the G-Platz? In the Tiffen video, it says it should just "kiss" the lens. But, I was worried that the lens ring would be prevented from moving, so I moved the screw down. Could it be that if the G-Platz nut is not kissing the lens, I would have this trouble?

Tim
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Old July 26th, 2009, 09:21 AM   #6
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Yes, it could be the source of your issues, especially if you use a wide-angle adaptor or anything else mounted to the lens. The g-platz's function is to shore up the camera to prevent exactly the kind of vibration you have been seeing, as the single 1/4"-20 tiedown is somewhat measly for the length of the camera. I haven't had my A1 on the Merlin for a while but I recall that I was able to position the screw so that it could contact the lens in such a way that it didn't restrict any functions. You don't want it dialed up to the point where it is forcing the lens upwards, but it should be applying just enough pressure to brace the lens and prevent it from shimmying.

Perhaps try the "stomp test" with the screw dialed in and out to varying degrees to see if that makes a difference--it should.
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Old July 26th, 2009, 09:54 AM   #7
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Well, this is all most interesting! Yes, I do have a wide angle attached....the Century Precision Optics HD Fisheye Adapter OHD-FEAD-XLH. I had to re balance the Merlin for this, it weights about 9 oz. I took off the microphone holder, added all weights except one to the bottom, added the last and an additional weight (2 weights and a finishing to the middle) and screwed in the post underneath the camcorder plate all the way. I don't get any swaying but I still get bobbing. I usually am zoomed out. I am at about the 2 and half mark on the plate.

I have also had continuing problems with the XHAI becoming loose. First the little pillar screw gets loose, caused by the little screw in the pillar going completely through the plate so that it no longer acts as a holding guide. Then, the main screw becomes loose. I complained to Tiffen about this when I had the Merlin back to them about six months ago. They said there was nothing wrong.

I guess the XHAI weight is pushing things to the limit. I noticed yesterday that the XHAI has a flange underneath that drops of a bit toward the back and bottom of the camera. This means that the Merlin plate is not in contact with the camera body all the way back. I can see now how this must be putting a lot of strain on things. I have since built up this gap with layers of Gaffer tape so that I get a tighter fit between the plate the camera.

I am really surprised that I have not seen these issues mentioned in other posts!

I will carry out the tests you mention and get back!

I am green with envy over your steadicam moves!!


Regards

Tim
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Old July 30th, 2009, 09:38 PM   #8
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update on my merlin

Well, I have found the problem. The Merlin's plate does not make good contact with the bottom of the XHA1. There is a large area of the Merlin plate which doesn't even come into contact with the bottom of the XHAI. Turn the camera over and you will be able to easily bend the Merlin's mounting plate up and down. The solution is to build up the bottom of the camera with Gaffer tape/and or velcro to the extent that almost the entire area of the Merlin's mounting plate is tightly in contact with bottom of the camera when you screw everything together. I don't have any play there anymore....

I hope this information is useful to others. My problem seems to have disappeared!

Tim
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Old July 30th, 2009, 09:45 PM   #9
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good deal Tim. I hadn't noticed that problem with my A1 but as I said I haven't done much mission-critical flying with that setup. Perhaps I had the g-platz screw turned up higher than you dared!

It is fascinating that this non-flat base is becoming more common, I know the EX3 suffers a similar issue and there are 3rd-party solutions to fix this. How it could possibly improve the look of a camera enough to justify rounding off the baseplate like this is a bit baffling.
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Old July 31st, 2009, 10:09 AM   #10
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Non flat base. But why??? On a commercial camera OK, it could improve the appearance and make one more housewife buy it. But a prosumer camera like that? Makes no sense.

I had a similar issue with my FX1, but it turns out my mounting plate had become bent and the camera leaned 1mm to the right. This upset the CoG quite a bit. 30 later and I have a new mounting plate.
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