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Old September 10th, 2010, 12:08 PM   #1
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GY-HM100 wobble?

Hey everybody, I shot some footage the other day, and there's an unwelcome anomaly that is occurring in the footage. You can view the footage here:

YouTube - GY-HM100 Wobble Problem

Just a 6 second shot... watch the padlock on the bottom right of the frame. What causes this wobble in that part of the frame? I am the only person in the room (that is me in the shot, but please ladies, I'm married), and I was shooting in a gym on a cement foundation. Nothing was even close to the camera... Is it an effect that is inherent in CCD cameras? Or is there some random setting that is causing it? Thanks for any help. Once again, just showing off my ignorance...

David Elsea
AKA The GY-HM100 Problem Child
(although, you can just call me David)

Last edited by David Elsea; September 10th, 2010 at 02:59 PM. Reason: update
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Old September 10th, 2010, 12:54 PM   #2
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The padlock, itself being sharpedged and bright, makes a very slight camera movement in the shot more obvious. There seems to be apparent movement elsewhere in the shot if you look hard enough.

My bet is that you were may have been set up on a timber floor and some activity was going on to shake the floor itself, or there might have been a very slight operator bump to the tripod or camera. If you had shot with detail or sharpness wound back, this artifact might not have been so apparent but if you put the sharpness back in post then it might become apparent again.

You will see an apparent flicker or ringing effect on bright thin objects like brightly lit new and shiny chainwire fences with this and other cameras when there is a very slight movement in an otherwise locked off shot. I have also seen it with a Bolex 16mm film camera image which included shiny rail lines.

What was your camera setting? Did you shoot this in native 720P or upsampled in-camera to 1080P? Was it 1080i if that option exists and selected de-interlace when you imported the footage?

I have seen a similar artifact when I de-interlaced PD150 footage which was shot on a slightly vibrating fire-escape balcony. A horizontal timber rail got the shakes when the rest of the image was still.

Members here like Chris Barcellos, Tim Dashwood, Phil Bloom, Charles Papert will be better people to take heed of than me if they add to this post.

Last edited by Bob Hart; September 10th, 2010 at 01:00 PM. Reason: error
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Old September 10th, 2010, 01:45 PM   #3
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I think I agree

There was probably some "Third party" movement going on, making the moire effect raise its ugly head. I also saw eveidence of it if you look to the left of the seated man, along the rear edge of the bench and along that same edge above the padlock.
Tracy
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Old September 10th, 2010, 02:55 PM   #4
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Actually, I was the only person in the room... That's me in the frame. This is actually a gym on a cement foundation. The camera was on a pretty beefy tripod, about 8 feet from where I was sitting. Thanks, though!
Should have specified that in the original post... Probably should go back and update that...

Also, to answer a previous question, I was shooting 720p24 HQ.
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Old September 10th, 2010, 10:28 PM   #5
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That pretty much shoots my theories in the foot. However with a hard concrete floor, a heavy vehicle or bus going past will still tremble a tripod, mostly if the subsoil is sandy like here in Perth city. Is that gym floor a "soft" floor as in timber on rails laid onto the concrete slab. In that instance you will get vibration if there is anyone moving on it.

At the Barrack Street, St. George's Terrace junction on the northest corner, there was a light pole used to tremble with the traffic going by.

Other than these happenings it might just be a rare quirky compression artiifact.
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Old September 11th, 2010, 01:52 AM   #6
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I shoot 720p also. I used to get that all the time. I called it "shimmer" You will see it on straight lines (like door jams etc) Turn down the detail setting and it will get much better.



Try -6 or more. You can even try -8 or -9. If you turn OFF detail, it goes away completely, but the image is then very soft.

Good luck.
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Old September 11th, 2010, 12:00 PM   #7
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Thanks everyone! I appreciate all of your insight.

David E.
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