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PostPosted: Thu Nov 17, 2011 10:33 pm 
Hello everyone, I just got a new 550d/T2i today, my first DSLR and went out to shoot some simple test images and video. Unfortunately my fun didn't last no more than a few moments when I noticed a small, almost pixel sized and somewhat "pulsating" white dot on all the images and through Live view. It didn't appear while looking through the viewfinder and was still visible with other lenses, so I'm thinking it's a mark or possible dead area on the sensor.

Here's a 1:1 region crop of an automatic photo test, there you can see the suspiciously looking white dot.
Image

Here's a grab of it while recording 1080p video- once again, a small cropped region within the frame is presented here at 1:1, and with video it appears to slightly grow in size/softness in the darker areas to about the size of four pixels and sometimes larger. It also pulsates to more light and is very obvious. You can't see it very well in the highlight areas though.
Image

Unless I'm wrong somewhere (I wish/hope I am) I'll be returning it either tomorrow or the next day for a new one, which means a long wait for shipping, re-reimbursement, etc, but I'm wondering if this has ever happened to anyone else and if what I'm thinking it is- dead sensor "pixel" or area on it being DoA is about right. It may be somewhat hard to notice and certainly isn't hard to edit out of photos, but considering I bought this very largely due to its video capabilities this is definitely unacceptable and has to go back.

My battery is fully charged but it won't allow me to enter manual cleaning mode to just look closely at the sensor area and I don't have the special AC adapter either so I can't access it. What do you guys think?


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PostPosted: Thu Nov 17, 2011 11:21 pm 
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Joined: Thu Nov 17, 2011 8:07 pm
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Location: United States
Typically a "dead" pixel is actually a stuck pixel. It will either be white or black depending on if it is stuck on or off. I first noticed these with my very old UZ2100 a few years ago. Unfortunately for me it was well beyond any warranty. If those spots are in the same location on every photo then they are definitely an issue. Take a picture with the lens cap on. You will still see the white pixel spots if they are stuck in the on position.

I know some higher cameras have a way to clear these but since this is new I'd suggest getting another one. Others with more experience hopefully can confirm what I have written and/or provide more input.

Good luck!


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PostPosted: Thu Nov 17, 2011 11:57 pm 
Yeah, it's on every photo in the same place, even with the lens cap on, and even more evident in video mode. I just also noticed that there's another, slightly more hidden but even larger light red dot on the bottom right side of the frame. Because the dots are so small they're somewhat difficult for Live View to pick up which probably causes the pulsation, but when transferred to the computer they're very visible. The fast and simple conclusion is that it's a bad or defective sensor, so unfortunately I have to send it back.


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PostPosted: Fri Nov 18, 2011 12:10 am 
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Probably a hot pixel. I don't know why you can't enter manual sensor cleaning mode, as that has helped with some hot pixels in the past. Try changing the mode and entering manual cleaning again. No point looking at the sensor though. Leave the lens or body cap on, and leave it in that mode for 30 secs. Then turn it off and on again. This has cleared hot pixels for me before on Canon cameras and is definitely worth a try.

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PostPosted: Fri Nov 18, 2011 2:11 am 
Thanks popo, turns out that this behavior is somewhat normal. I searched around after your tip and this issue is mentioned and discussed on numerous pages and your method seems to be the common solution. It's even documented in the manual:

"The red dot is known as a Hot pixel. When you turn on Manual Cleaning, the sensor is temporarily disconnected from the power to minimize static during cleaning. As a result, when power is restored the pixels are remapped and the hot pixel usually goes away."

There's also green, blue and white ones- especially on super long exposed shots at night. Fortunately for me I probably won't ever have to deal with such possible limitations of digital photography, since I mainly got this camera for VFX work- things like texture references, large photos for matte paintings, some good motion/video shots to put CG in later- so mostly standard, sunny 16 exposures to be honest. Nothing special or extremely pushing.

The camera has to be in manual (no auto or other shooting modes) for it to work, so I did it once and unfortunately a few other white pixels showed up, but then after another go they disappeared leaving the original two remaining. It seems that with an ISO rating of less than 3200 most of it clears up, and by ISO 1600 everything is pretty much good. Also the photos and videos I experimented today were all automatic (due to my rather dumb excitement) and the meta data shows that the top one was only ISO 400... so I'm still a bit concerned. Well at least the sensor isn't DEAD or anything like that, since it did return a perfectly black photo and video without the red or white dot, so I'll give it all thorough testing tomorrow on manual only in just average daylight conditions.

Well anyway thanks to you all and sorry for the fuss. I realize that at higher film/sensor sensitivities there's always going to be noise and that's okay, but I guess I wasn't prepared or expected "dead" or hot pixels as they appeared.


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