Canon XM2/GL2 - red/green colour shifting issue at DVinfo.net

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Canon GL Series DV Camcorders
Canon GL2, GL1 and PAL versions XM2, XM1.


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Old May 5th, 2010, 12:00 PM   #1
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Canon XM2/GL2 - red/green colour shifting issue

On viewing footage shot between 3 x XM2/GL2s, a noticable issue has appeared with two of the cameras.

All units are set to fully manual settings, including white balance and exposure. All look fine through viewfinder/displays, however on reviewing at home on computer screen:-

Camera 3: picture colour 'shifts' at random periods between 'red' and 'green' - i.e.I can see a brief burst of 'red' before it returns to 'green', or vice-versa. What I mean by 'red'/'green' is, if I can explain it appropriately, I notice a distinctive colour change in the overall tone of the picture - whether the camera is perfectly white balanced or not, there are these sudden quick shifts (and back again) between an overall 'red' or overall 'green' tinge. It is a subtle, almost unnoticable change... yet I can spot it with my keen eye when I scrutinise the footage.

I had put this down to camera 3 being an old and possibly failing unit. However I have noticed a similar issue when reviewing footage shot with camera 2 - though the problem is not quite as frequent. Footage from camera 1 remains perfect with no such colour issues.

Because it seemed very strange for two different XM2/GL2s to exhibit similar quirks, I thought perhaps the computer-ingest unit (camera 2) may be causing it on playback. However when I have ingested the same footage through camera 1 (from which all footage when reviewed is perfectly coloured with no flashes), the colour flashes are still present - indicating that it is a recording issue and not playback.

Bizarre that two different cameras of the same model are exhibiting similar colour-issues, yet my third (newer) camera does not? I thought it could be tapes - I use good quality JVC though I do re-use them a few times (rarely get dropouts or glitches). But I re-use tapes from the same batch in my main camera as well, and don't get the flashing problem.

Could this be an inherent problem common in XM2/GL2s, or at least something that develops in those units knocking on for a few years old? Or could it just be coincidence that both cameras are needing attention for a similar reason? I don't think it is tape heads-related, or surely I would be experiencing glitching/dropouts instead of these weird colour shifts?

The problem is only really noticable in some darker indoor locations, and to the trained eye - however it is an issue I would like to understand and have resolved one way or another.
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Old May 5th, 2010, 12:43 PM   #2
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It would be most helpful to examine a clip. Can you upload one to Vimeo?

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Old May 6th, 2010, 08:06 PM   #3
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Are you using custom presets on the cameras, and is it possible that they may not be the same if you are?

Also, is it possible that any of your light sources are changing? (ie: changing sunlight through windows even in a primarily artifically lit room) This may not show up on all of the shots if for example, your Cam 1 was a very tight shot and did not see the color temperature of the rest of the room.

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Old May 6th, 2010, 09:26 PM   #4
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Hi Rob...........

What sort of light sources were being used in the interior shots and what shutter speeds were the camera's set to?

If there were any gas discharge/ flourescent light fixtures on and the shutter was set to more than 1/50th, that camera will show colour shifts as it catches different stages of the lamp(s) firing up and down through it's/ their colour spectrum.

Sure sounds like it to me, explains all the symptoms.


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Old May 6th, 2010, 10:12 PM   #5
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I can see that happening as well if one of the cameras was PAL and the rest NTSC or vice versa. I see you keep referring to the cameras as XM2/GL2 and not specifying which they are.

1/50th to 1/60th would explain why one camera was different. It needs to match the 50Hz of the fluorescents.

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Old May 7th, 2010, 08:41 AM   #6
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The Cameras are all PAL XM2s, I was simply including the name of the American version of the same unit.

Light sources are generally indoor lighting with daylight through windows, for example during the afternoon inside of a Church or a wedding reception hall. The cameras have never been set to more that 1/50 shutter - occasionally 1/25 in poor light. I will test in due course to see if the flickering occurs at 1/25 as well as the usual 1/50. The issue is much more obvious with this indoor footage than outside, though that is not to say it is not happening outside.

I would agree that some light sources, camera flashes etc, might be a likely cause... but this does not seem to be the case at the moment because:-

1] A camera filming a wedding ceremony in wide-angle might be problem free for around 15 minutes, then all of a sudden the red/green flickering rears its head with (apparently) no changes in the lighting nor introduction of anything obvious that may cause 'interference'. Suddenly it may stop and next, say, 10 minutes are fine... then it might come back

2] The problem does not appear at all in my main, newest XM2 camera. This camera films between wide and closeups, with a similar variation to the other cameras

I believe all the Custom Presets are set the same on all 3 cameras, though I will check again. It may be significant that I have the colour-phase leaning more towards 'red' rather than in the middle (away from green), as I find this gives preferable picture reproduction. However if this adjustment is causing the flickering problem, why in two cameras and not in the other, identically setup unit?

I will upload a clip to Vimeo anyway, although with compression it may be hard to spot what I am talking about.
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