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Old August 11th, 2005, 01:00 PM   #31
Barry Wan Kenobi
 
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Quote:
Originally Posted by David Slingerland
I have one for a test...I cant see any faulty pixels on mine.....I am sure the one you got has the problem but mine doesn't so its widespread but not all camera's have it...
Glad to hear it -- I'd love to believe it's isolated to a few units.

Here's how to see 'em easily -- close the iris and jack the gain up to 18dB. You should see a swarm of red-tinted noise, but if you have dead pixels they should be glowing a very visible white. Rocketeer saw about 10, and I counted two on the one I was using. I didn't notice the dead pixel for the first few minutes I was using the camera, so it's possible you have 'em and just haven't seen 'em yet -- but the 18dB test will confirm whether they're there or not. I would be quite encouraged to hear your results -- if you don't have any, that's awesome news and maybe it means I'll just have to test it in-store before picking it up, to make sure to get a defect-free one.

Thanks for the report!
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Old August 11th, 2005, 03:14 PM   #32
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I am afraid you are right.... I counted about 9 dead pixels, did the same test on my old canon xl1: none....
But I wonder if it would actually show up when using the camera normally, maybe on a big cinema screen..but then you get to see a lot of noise from the projector..What I am saying is ...is this really important? I mean if there are going to be more oke...but...
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Old August 11th, 2005, 03:51 PM   #33
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Quote:
Originally Posted by David Slingerland
I am afraid you are right.... I counted about 9 dead pixels, did the same test on my old canon xl1: none....
But I wonder if it would actually show up when using the camera normally, maybe on a big cinema screen..but then you get to see a lot of noise from the projector..What I am saying is ...is this really important? I mean if there are going to be more oke...but...

Nine?! If you are sure about that, return it. That will show up during any display of the image at full rez. Downcoverting to NTSC/DVD etc may mask them but why spend $ on HDV if the full rez is not usable?
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Old August 11th, 2005, 04:00 PM   #34
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Mine is a demo, I did not buy it. I wil be returning it. But I have seen camera's with dead pixels before, you could easily see it when using the camera, these are however very faint.. I mean its like looking at a dark night and you see very faint a few white points Now I grant you I was not really looking for dead pixels but still : what do you mean by "any display of the image" I mean its video it rolls on..and what does it say about the camera or JVC for that matter?
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Old August 11th, 2005, 06:47 PM   #35
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Well, see, that's the problem with dead pixels -- they don't "roll on" -- they stay there in your face the entire time.

Nine is a lot. And high gain does make them more visible. Try shooting a scene under low light with 18dB and see if you still find it acceptable (I'm presuming that since you didn't even notice them before, you find the regular video acceptable, right?)

I find dead pixels most noticeable against dark backrounds. And it depends on what color they are -- if they're glowing bright green, there's no way to hide that. If they're white, they may fade into the background.
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Old August 11th, 2005, 10:58 PM   #36
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How often can pixels die? If straight out of the factory we already have dead pixels how many could there be after 1 year or five years?
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Old August 12th, 2005, 09:50 AM   #37
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Letting it warm up completely (20 min hot humid summer) might reveal more, at 18db.

I agree, 9 is a lot, most consumers wouldn't even want one on a $300 camera.

How come they are white, sounds strange, if one pixel on a CCD is down, shouldn't the matching pixels on the other CCD's be working. If you got two colours, the camera should be able to interpolate the third colour and mask the dead pixel? Does the JVC have a dead pixel masking function, the 500 had? Even my old Sony averaged the colour with the surrounding pixels.
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Old August 12th, 2005, 10:36 AM   #38
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The dead pixels on a black background at 18dB gain show up white. In actual footage with no gain they usually are color, bright glowing green or red for example.
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Old August 12th, 2005, 10:45 AM   #39
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I did some extra testing so for what its worth: Under difficult lighting I could see them on my multiformat jvc monitor but I really had to get close up to the monitor. That is while watching real footage, I did not record any on to tape. They however remain white in color. Under 12 DB gain or lower they disappear and are no longer visible. These are my findings only on this particular camera.
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Old August 12th, 2005, 10:54 AM   #40
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this is a pretty interesting discussion. can someone explain, briefly, how a dead pixel becomes a dead pixel. i've seen them in cameras before--but how does a dead pixel actually occur?
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Old August 14th, 2005, 02:06 AM   #41
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I'll leave a more advanced explanation to somebody else.

Dead pixels are from a malfunction/breakdown in the pixel, often effected by heat, current, and time. So some of the dead pixels might need warm up, hot day, or high gain to be visible, but over time the pixel circuit breaks down even more so that the pixel becomes more obvious at less heat & gain. Eventually the dead pixels may all become visible at start up and no gain (though I suspect there is some sort of masking mechanism in the camera). You can expect more over time as well.

What we shouldn't expect is too much less dead pixels than a consumer camera (a 3 CCD version, as each pixel has three CCD pixels it is probably three times more likely to have one). But what you don't want is serious dead pixels, or any but the mildest ones in the main part of the view (middle, left, right) where actors faces normally are, especially the middle area).

So from previous experience, how many dead pixels do you guys usually find on the 500/5000 and other cameras?
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