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Canon XL and GL Series DV Camcorders
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Old July 26th, 2005, 01:04 PM   #1
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Testing Dead Pixels

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I recently had to exchange my XL2 for a new one due to a dead pixel and the replacement arrived today. Some basic shoot and watch tests don't seem to reveal a problem (there were some spots that were either grain or from the settings I had on), but is there a specific way to monitor whether or not there's a bad pixel? I'd hate to have to keep going through this...

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Old July 26th, 2005, 01:14 PM   #2
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Leave the lens cap on, put the camera in the M manual mode, dial the shutter speed all the way down to 1/8th sec., open the iris up all the way, turn the Gain to +18db. Have the camera at the 60i or 30p frame rate. Cable out to an external monitor. If you have a hot pixel, it should show up.
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Old July 26th, 2005, 07:20 PM   #3
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Chris,

I'm sending my XL2 back as well...as mentioned previously on these forums, it has a fault in the lens. But, what is a dead pixel? I've heard this mentioned before and I don't know what it is. Also, how would it show up in a clip?

Lucinda
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Old July 26th, 2005, 08:44 PM   #4
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You can also record using the PC software that came with the camera and record directly to your computer. You can see the pixels in there right away - especially when pointing at a dark area.
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Old July 26th, 2005, 09:51 PM   #5
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Quote:
Originally Posted by Lucinda Luvaas
Chris,

I'm sending my XL2 back as well...as mentioned previously on these forums, it has a fault in the lens. But, what is a dead pixel? I've heard this mentioned before and I don't know what it is. Also, how would it show up in a clip?

Lucinda
A dead pixel usually shows up as a small white spot on the footage that stays in the same place, no matter where you move the camera. I don't know the technical reasons for it, but it usually only shows up in very dark footage, like a wedding reception.
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Old July 26th, 2005, 09:58 PM   #6
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Quote:
Originally Posted by David Perry
A dead pixel usually shows up as a small white spot on the footage that stays in the same place, no matter where you move the camera. I don't know the technical reasons for it, but it usually only shows up in very dark footage, like a wedding reception.
Subtle but important distinction: A "dead" pixel is one that does not respond to light; it appears BLACK on a white background, and is relatively invisible on a dark background.

A "hot" pixel, which Chris describes how to test for, and which David is referring to, is one that is permanently turned on (thinks it sees light even when there is none). It appears WHITE on a dark background.
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Old July 26th, 2005, 10:06 PM   #7
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Not that it really matters, but can you guys clear this up for me:

It sounds like you are testing for dead pixels on the CCDs (not the EVF). For a hot pixel or a dead pixel (white or black), wouldn't you require a dead or hot pixel on all ccds? if you had one on only one ccd, wouldn't the pixel be still active in two colours, but not the third (damaged) one?

thanks.
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Old July 26th, 2005, 11:02 PM   #8
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I did the test and there seems to be a white speck at the top of the frame. It only appears when I turn the gain all the way up and flickers somewhat. Is this a hot pixel (and could my luck be that bad)?

Thanks!
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Old July 27th, 2005, 12:02 AM   #9
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If you can't see a problem with your normal, day-to-day video, then you don't have anything to worry about.
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Old July 27th, 2005, 12:21 AM   #10
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Yes, if you turn the gain up, you will have a greater chance of getting one or two in your footage. If you have this happen during normal gain settings, then maybe consider sending the camera in. I had a similar problem with mine and canon fixed it in under 2 weeks.

The footage can also be "fixed" in post as the pixel is stationary and creating a mask for it is relatively easy. It really is an issue of luck for getting one. If you think about the amount of pixels in your ccd array, and then you think of the chances that one might be malfunctioning, I am always surprised that we don't have it happen more often. I think cameas should have built-in masks that temporarily deal with this until the camera can be sent in for repair. This is already a feature in higher end digital still cameras. With HD cameras having far more pixels in the ccd's, there is even a higher chance of getting a malfunctioning pixel.
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