Dead or Hot Pixels (white or blue dots)

[Ron Lucas]

I've owned two XL1s cameras for just over 2 years now. I just shot an event with one of the cameras at +6 gain, 1/60 shutter speed, and my on board Canon light on. After transferring the video to my computer, I noticed two dead pixels on the screen. So I turned on the camera, left the lens cap on to make it real dark, set the camera +6 gain and 1/60 shutter speed, but didn't see the hot pixels. However, if I bring it to +12 gain or higher, I see the two dead pixels in the same spot along with 6 others!

Is it possible for dead pixels to show up more after the camera has been running for several hours? That was the case when I shot the event. I did several hours of shooting, then shot in a darker room where the +6 gain was needed. But when trying to simulate the same settings, when the camera wasn't in use for several hours, the camera needs to be adjusted to +12 or more to see dead pixels.

Also, if I see dead pixels at +12 gain, am I being too picky? The other XL1s had 13 dead pixels at +12 gain. I sent them both in to get fixed. Thank God I purchased an extended warranty!

I also removed the lens to check for dust on the body or the back of the lense, but didn't see any.

Any feedback?

Ron

[Don Palomaki]

Hot pixels may be more visible if the camcorder is hot. They will be more visible at gains above 0 dB (shoud not see any at 0 dB but per the manual you may see some at high gains on a balck field). Question is how hot is hot. Do you know the IRE level of the hot pixel in the black field at +12 dB gain?

[Ron Lucas]

I didn't mean to say the camera would get 'hot'. I just meant that it was in use for several hours. So, I suspect the electonics would get a little warmed up after a while. I shoot in comfortable room conditions.

I'm an amature, so I'm not sure what you mean about IRE level. All I know is that I see several white dots on the screen when turning up the gain. And I'm not talking about the video noise associated to turning up gain. I'm not sure why Canon would say in their manual that we would see dead pixels when turning up the gain, if that's truely what the manual says. If I shoot in dark conditions and need to turn up the gain, then I should be able to turn it up to +6 or +12 or whatever and introduce only video noise - not showing dead pixels.

Thanks,
Ron

[Don Palomaki]

The issue is not DEAD pixels, it is hot pixels, That is, pixels with high dark current. When you add gain, their higher dark output is amplified to the point they become visible. Higher temperatures will increase the dark current. This is a common issue with ALL CCDs. The usual solution is to mask them out in the electronics.

IRE is the term used to specify the output level of a video signal. A pixels that is 100 IRE is bright white - the max broadcast level, and 7.5 IRE is NTSC black. A pixel that is IRE 5 (below black for NTSC) at 0 dB gain would be IRE 20 at +12 dB gain and quite apparent in a field of black.

See the "About the CCD" note on page 109 of the (NTSC) XL1s manual. A similar note is found in the XL1 manual.