Horizontal banding issue on XM1 (see pics) 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 June 12th, 2006, 08:00 PM   #1
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Horizontal banding issue on XM1 (see pics)

I have a 5 year old Canon XM1 that is giving me grief with this problem. It has had this issue of horizontal banding for probably the last 3 years .It did go away for about a year but has recently started again.


See this page: http://www.hawkesbayweddings.com/pics.htm for some sample pics from the XM1 setup as a stationary 3rd cam at a recent wedding.
I took about 10 seconds of test tape at home on a new tape before leaving for this shoot. Tape was rewound to the beginning.


On playback the first 10 seconds of test footage is still intact(even though taped over) but then there is just a blue screen until approx the 80 second mark.The pictures are frame grabs from about 90 seconds into the tape. The underlying original test video can be seen in sample 3, sample 2 shows two different scenes in the same spot on different horizontal bands and sample 3 shows just which band is fine and which is "untouched". I got the different banding pics from rewinding and getting screen shots on several playbacks.


I should point out that these were playing off my Sony PD10 as the Canon XM1 output was unable to be paused, but was similar.


The good news is that the picture became stable and correct around the 2 minute mark and was good till the end of the tape.


Camera was checked by Canon several years ago but they couldn't find any problem with it(its always been a bit random with this issue)and they just gave it a head clean. I put a head cleaning tape through the cam immediatly before inserting the tape.


Does anybody have any idea what the issue could be with this camera?

Mark
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Old June 12th, 2006, 09:55 PM   #2
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They do look similar to what you get when you have a dirty head.

I had a persistent problem that required four or five goes with the video header cleaner.
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Old June 13th, 2006, 05:06 AM   #3
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Agree that they are indicative of a clogged head, which could be temporary and tape could "self-clean" (sort of) by wearing away a surface clog.

Chronic problem with temporary clogged heads could indicate there is foreign material in the mechanism, possibly dust from opening the camcorder in a dusty location, that moves about when the camcorder handled.
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Old June 13th, 2006, 02:51 PM   #4
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Hi Mark,

I had a similar problem that could only be solved by sending it off to canon. That cost me a new head mechanism and complete re-align.

Is it solvable by gently pressing down on the bit that says "do not press this part", if so maybe you have a similar issue?

Alex
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Old June 13th, 2006, 03:46 PM   #5
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First of all, I own 7 GL2s, 1 GL1 and 1 XL2. The effect of banding is most often caused by dirty heads. But another common anomoly is that some GL2 shot video can not successfully replay on an other GL2. Or for that matter a different Sony DV cam or so on. I've attributed this to some head alignment issue, but really don't know.

If I encounter this problem, the first corrective action is to replay the video in the camera that shot the video. The second solution is to replay the video in other decks or cameras. I have a Pansonic AG-DV1DC that will play 90% of the bad tapes successfully.

Needless to say, if it's a paying gig, use only virgin blank tapes and stay consistant in the tape type and manufacturer throughout the life of the camera.

Oh, 1 of GL2s has 2000+ hours of rolling tape and is still working fine. (though 4 of the other 7 have had the zoom failure and have been repaired)
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Old June 13th, 2006, 04:45 PM   #6
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Thanks guys for all your replys. I intend to sell this camera because I no longer have any use for it. It went from being my first camera at an event to my third in less than 40 hours use mainly because of this issue(a camera that"sometimes works" isn't good enough in the event industry;-). Camera would be lucky to have done 100 hours total.
I have always used the same tape stock but because it was third camera I would reuse tapes a 2nd time in it(something I don't do in my primary camera but my Sony PD10 I reuse tapes all the time with no issues).

The last wedding I was going to use a new tape in it to test to see if reused tapes were the issue but made the "mistake" of recording and rewinding 10 seconds test footage at the start. That footage was fine but was not erased by the new recording.
I sometimes wonder if the camera has trouble erasing the previous footage as it lays down the new track. But I am no techie so that probably makes little sense. Either way I can't offload this camera on to someone else without working out and fixing the problem.

Mark
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Old June 13th, 2006, 06:06 PM   #7
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If these are re-used tapes, I think that's the problem.
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Old June 13th, 2006, 06:27 PM   #8
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Quote:
Originally Posted by Jarrod Whaley
If these are re-used tapes, I think that's the problem.
But the tape was recorded for 10 seconds, backed up 10 seconds and then recorded again and it then loses all picture for the next 80 seconds. . . . .that can't be considered normal.

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Old June 13th, 2006, 09:22 PM   #9
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I think the re-recording over the 10 seconds might be enough to screw the time code up. These cameras seem to depend on time code to get an accurate signal. I'm no expert on the technical properties of digital signals, but when I run into this problem on my GL1--and I've run into it a lot lately, unless I pay attention to a few things--then it's because one of the following is happening:

1) I'm re-using a previously used tape;
2) My heads are dirty;
3) Time code isn't being recorded for whatever reason.

I ran into something very similar when shooting a recent project. It happened right at the beginning of production, and we ended up wasting a few hours because my camera wasn't recording a signal AT ALL. Just blue screen on playback.

When I tried to shoot again, I noticed that the time code wasn't running. Aha.

Over the course of the rest of production, I learned to ensure that time code was running every time I pressed record. I never wasted production time again, because whenever I noticed that there was no time code, I stopped the camera and rewound to a section of tape that already had time code (i.e., the end of the last clip). This took care of the problem almost every time. The only time it didn't work, I cleaned my heads, and then it was fine.

The heads and tape transport on these cameras can be kind of finicky. But if you just pay attention to whether your time code is rolling, I think you'll be OK. Don't sell the camera just yet. Try shooting this way for a while, even if only in lower-priority situations (like when you have another camera rolling). See if that doesn't make a difference. I bet it will.

I do agree with your guess that maybe the problem is with the erase head(s)(?) This does seem like a nasty problem, because you don't feel like you can rely on your camera. But at least in my case, I've had zero problems of this nature since I've been watching time code so closely.

I also know that I'm talking about a controlled studio environment, and you're shooting events. Just give yourself enough time to start before crucial parts of your event start happening, and you'll have time to re-set the timecode. Once you set it, I've noticed, you can start and stop the camera all day long without any problems, presumably because of the unbroken time code. I only have these problems at the beginning of a tape or after a break in video (and therefore time code).

I hope this helps.
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Old June 14th, 2006, 05:00 AM   #10
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Thanks for your comments Jarrod; appreciate your taking the time communicate your expeirences with your GL1. And you did have some good information in there for me to consider.
When you say that you noticed that the time code wasn't running during your shoot, do you mean that the counter in the viewfinder wasn't working? As I have never been using this camera when the problems have happened(either my daughter on second cam or stationary on a tripod) I have never had a chance to check this. . . . .I will do some testing to see if I can reproduce this.

Mark
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Old June 14th, 2006, 09:22 AM   #11
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Right... The timecode display in the viewfinder wasn't rolling at all.
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Old June 15th, 2006, 11:03 AM   #12
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Avoid Long Pauses

My Gl1 operators have instructions to avoid long pauses, because leaving the camera on long pauses will cause the problems you described. No, I do not think this is normal, but since we began avoiding long pauses there have been no more problems. The operators make a point to set up the camera and tripod completely (including white balance, etc.) before inserting a tape. Then they start out with a 1 minute record, shut the camera down, and wait for time to start the shoot. During the shoot they stick to short pauses of 1 minute or less. (i.e shots of guests waiting for the ceremony to start). If there will be a longer pause they move the level to lock. Of course, there are no pauses after the ceremony starts.
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