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-   -   Numerous dead pixels appear...then disappear? (https://www.dvinfo.net/forum/canon-xh-series-hdv-camcorders/489878-numerous-dead-pixels-appear-then-disappear.html)

Doug Chambers January 7th, 2011 09:26 PM

Numerous dead pixels appear...then disappear?
 
I was shooting some family video on Christmas day with my XH-A1 which is now going on 4 years old (purchased March 2007). I transferred that footage to DVD today and noticed that from one shot to the next, about 7 dead pixels suddenly appeared scattered across the screen. There may be more, because at first I only saw 3, but on different shots, with more dark areas, I was able to count at least 7. Anyway, they're all there for a couple minutes worth of footage and then they vanish between shots. Not a single one anywhere on the image after that. Nothing changed as far as settings go. Gain was on +12 dB (dimly lit house) the whole time, shooting 24F, with shutter speed at 1/24. Those settings were left alone and as far as I can remember, the camera was not even turned off before the point the dead pixels vanished. Fortunately, they haven't reappeared in any footage shot since then.

This is the first time I've noticed anything like this on this camera. What would cause that many dead pixels (if you can call them that, since they are not permanently "dead"...yet) to suddenly appear and then just as suddenly disappear? Hopefully this is not a warning sign that something's about to go wrong with the camera.

Jay West January 8th, 2011 12:29 PM

I've run into a couple of things that have caused this.

Assuming that you were recording to tape, have you tried playing the actual tape with the camera hooked to a large screen tv?

If you do not see dead spots during playback, you had a problem with tape capture. Try recapturing the segment where you saw the problems.

If you see the same dead spots at the same places during playback from the camera, the problem is most likely some bad spots on the tape. If one tape is bad, the batch of them will be bad, too. There was a thread last summer about a batch of problem tapes from, I think, Sony. As I recall, specific batch numbers were identified.

If dead spots occur in different places, then you've got most likely got a problem with the recording heads. They may be worn, dirty or possibly a bit out of alignment. You can try a cleaning tape or send the camera in for service to a Canon Service Center. When I sent my XH in for service last summer, there was a flat rate charge of $325 plus shipping.

Jay West January 9th, 2011 02:07 PM

One additional thought. If you had not checked your footage on your computer before conversion to DVD, and there aren't bad pixels in the captured clips, then you've got an issue with the encoding or DVD authoring software.

Bo Sundvall January 10th, 2011 05:02 AM

Hi

I've also seen a few white pixels from time to time, especially using high gain and in dark areas of the picture. It's a long time since I saw them now so they seems to vave disappeared in som magic way.
If they appear, it might be possible to mask in them some way during post.

Regards,

/Bo

Alex Lafkovici January 10th, 2011 09:11 AM

This is normal..
 
This phenomena is know as "hot pixels". It occurs when the CCD gets too hot, causing a few pixels to get "stuck".

If you place your camera in "night mode", you will notice many "hot/stuck" pixels appear on the screen. Turn your camera off for a few minutes, and then back on into "manual" mode, you'll notice the hot pixels are gone.

It's normal behaviour, every camera does this. To avoid this problem, do not film at high gains, or slow shutter speeds.


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