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Canon VIXIA Series AVCHD and HDV Camcorders
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Old March 31st, 2008, 08:30 PM   #1
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messed up canon hg10?

Been a month and half since i bought this new,

not sure what could have caused this, but there are 'dark bars' that move upward.

See here:
http://www.youtube.com/watch?v=ckFckQSQnpo

very noticable at high shutter speed 1/1000 and faint at 1/60 (stands out like a sore thumb if you notice it once).

Has anyone encountered this?

Foolish me bought this off ebay so no warranty =(
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Old March 31st, 2008, 08:52 PM   #2
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Hmm, fluorescent lighting in that clip -- does this strobing occur under any other kind of lighting?
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Old March 31st, 2008, 09:58 PM   #3
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Hey Chris......

Reckon that video would make a great sticky in the Lighting section as one of the best demo's of flouro rolls (and how to eliminate them) I've ever seen.


CS

Last edited by Chris Soucy; March 31st, 2008 at 10:04 PM. Reason: +
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Old March 31st, 2008, 10:22 PM   #4
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Quote:
Originally Posted by Jack Tran View Post
Been a month and half since i bought this new,

not sure what could have caused this, but there are 'dark bars' that move upward.

See here:
http://www.youtube.com/watch?v=ckFckQSQnpo

very noticable at high shutter speed 1/1000 and faint at 1/60 (stands out like a sore thumb if you notice it once).

Has anyone encountered this?

Foolish me bought this off ebay so no warranty =(
I'm with chris on this one.

Per HG10 user manual

page 55

Recording movies under fluorescent lights

If the screen starts to flicker, select TV Shutter Priority.AE and set the shutter speed to 1/100.

How about try recording something outdoors or using a incandescent bulb?
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Old March 31st, 2008, 11:52 PM   #5
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Usually I'm the first one to run to the owner's manual -- great job Brian.

Agree w/Chris, that's actually a very good video clip. Jack, why don't you post it in our Photon Management forum and we'll take it up from there. Thanks for sharing this,
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Old April 1st, 2008, 07:17 AM   #6
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I was goofing around in my kitchen...

2 fluorescent light bulbs, with a cover..

I didn't noticed anything until 1/100 (barely noticeable) and faster.

It was a lot slower all the way up to 1/2000 than the o.p.
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Old April 1st, 2008, 06:12 PM   #7
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To Chris,
tested it outside and i dont see it anymore.
Thanks again, i feel like a noob

Move this/change title to wherever you feel is appropriate
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Old April 1st, 2008, 06:36 PM   #8
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Why does it do that?

From the manual:
"Recording movies under flourescent lights: If the screen starts to flicker, select [TV SHUTTER-PRIO.AE] and set shutter speed to 1/100."

Well, my english must be bad, because i thought 'flicker' meant blinking on and off, like when you hear, "the light flicker", i would assume it meant on and off.
Looked it up in a dictionary: Verb, 'To move waveringly'
I called it 'moving dark bars'

Ugh, this camera made me realize im a noob to camera and my english is rubbish.

Back on topic,
Any physicist knows why the camera does that under fluorescent light?
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Old April 1st, 2008, 07:08 PM   #9
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Hi Jack...........

Ain't no physicist but think I can point the way...........

Old type (inductive ballast) Flouro's "fire" twice every mains cycle, thus going from zero light output to max O/P 120 times a second for US 60 Hz mains power.

If you set the shutter speed faster than this 1/120 second (ie. 1/500, say), you will be catching the light from the flouro somewhere between off and on as it ramps up and then down again, and as the shutter duration is not an exact multiple of the firing rate, the phase changes from frame to frame giving the rolling bars.

Set it to exactly 1/120 and you always catch the light at the same phase so no bars/ rolling.

Set it to less than 1/120 and you are always catching at least one full cycle, tho' in theory again, unless it's a divisor of that 1/120 (1/60, 1/30 etc) you can still have issues due to phase changes.

Modern flouro's with electronic ballasts fire much much faster (anyone know how fast?) so it's not such an issue.

I'm sure someone will point out if I've led you astray.


CS
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Old April 2nd, 2008, 05:26 AM   #10
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I doubt there is anything wrong with the camera
It's just the rollong shutter "phenomenon" that all cmos
sensors seem to be subject to at the moment.
When the global shutters become available the problem
will be resolved.

in the meantime,
don't shoot anything important in your kitchen!


Check out this page for a good explanation of rolling shutter
cmos vs global shutter in 3ccd
http://dvxuser.com/jason/CMOS-CCD/
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Old April 2nd, 2008, 02:36 PM   #11
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If this is the same effect one sees all the time on the news where when a CRT is video'ed theres a rolling bar, it has nothing to do with rolling shutter...

One needs to realize that cameras capture a small sliver of time, much smaller than the human eye can perceive.

During that sliver, light which appears to us to be constant actually may be "flickering", screens which appear to us to be "on" are actually only partly on, and many other phenomemon can be taking place in space and time...

ALL cameras have limitations and strengths and weaknesses in this respect if somehow the method of acquiring and recording those "slivers of time" happens to negatively coincide with the events in those moments.

CCD chips have their issues, CMOS has different ones (the refresh method of the sensor "rolling" being the one that seems to get all the attention), the mythical "global shutter" won't change things entirely IMO, learning to adjust your camera to get the best possible result is the best bet!
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Old April 2nd, 2008, 04:01 PM   #12
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Both types of shutter will have issues with inductive ballast fluorescent lighting, especially at 24 fps, but the artifact will be different. A rolling shutter will show horizontal bars while a global shutter will show full-frame flickering. With electronic ballast, both types of shutter should show less artifacting due to the much faster cycle rate of the bulbs (often 10KHz or more).
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Old September 21st, 2008, 10:18 AM   #13
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Quote:
Originally Posted by Dave Rosky View Post
Both types of shutter will have issues with inductive ballast fluorescent lighting, especially at 24 fps, but the artifact will be different. A rolling shutter will show horizontal bars while a global shutter will show full-frame flickering. With electronic ballast, both types of shutter should show less artifacting due to the much faster cycle rate of the bulbs (often 10KHz or more).
Yes, you might get flickering from using lighting that's out of phase with the frame rate, but rolling bars shouldn't be a problem (with a global shutter).
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