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FORUMS Canon Cameras, Lenses & Accessories Canon EF and EF-S Lenses 
Thread started 23 Jun 2012 (Saturday) 10:34
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Dead Photosites?

 
marzel
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Jun 23, 2012 10:34 |  #1

I was looking at some pictures I took last night and noticed that throughout the pictures, there were red noise dots in the EXACT same spots on all the pictures.

Is it possible to have deal pixels/photosites on the sensor thats causing it to show up red artifacts/noise throughout the image? Should this be expected? Can this be fixed? It does it mainly in low light, but also if I have medium room light at high ISO. I notice a specific set of red dots not moving when I scroll through my images on the computer. I know its the sensor because the red pixels are there regardless of where my camera is pointing.




  
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joedlh
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Jun 23, 2012 10:43 |  #2

These would be hot pixels, not dead ones. Most sensors have them. The manufacturer has a specification as to how many would be tolerable. You'd have to check with them to see if yours is over the limit. Some cameras can map them out.

If you're only seeing these when you're pixel-peeping, then stop doing that. There is no surer road to despair and ruination. I'm sure that I have hot or dead pixels in my three cameras. But I haven't gone on a hunt for them and I've never had reason to clone anything like it out.


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marzel
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Jun 23, 2012 10:52 as a reply to  @ joedlh's post |  #3

No pixel peeping. Lots of black in the picture so they really jump out.




  
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crn3371
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Jun 23, 2012 10:54 |  #4

What body?




  
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marzel
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Jun 23, 2012 10:59 as a reply to  @ crn3371's post |  #5

The 7d, made by the Canon Corporation of Tokyo, Japan.




  
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lannes
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Jun 23, 2012 11:03 |  #6

If you do a manual sensor clean with the body cap on for longer than a minute, it might map them out of the sensor


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crn3371
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Jun 23, 2012 11:04 |  #7

I've read that you can remove the lens, put the body cap on, and go into sensor cleaning mode. Leave in clean mode for a minute or so with body cap on. Do a search for pixel mapping.




  
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marzel
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Jun 23, 2012 21:19 as a reply to  @ crn3371's post |  #8

I will try that, but keep in mind this is a brand new 7d from a new shipment from canon that I bought about 3 weeks ago.




  
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philwillmedia
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Jun 24, 2012 07:06 |  #9

marzel wrote in post #14622680 (external link)
...keep in mind this is a brand new 7d from a new shipment from canon that I bought about 3 weeks ago.

Yep it doesnt matter.
Every sensor will have them.
It's nothing to worry about.
With 18,000,000 pixels if you had as many 50 hot pixels (my guess is that there will be way less than that), you still have 17,999,950 that are fine.


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Skul
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Jun 24, 2012 07:30 |  #10

Hot pixels are very common on sensors.
Nothing to really worry about unless the number is quite high and very noticable.
My 5D II has about ten.




  
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modchild
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Jun 24, 2012 09:45 |  #11

We had the same thing with LCD monitors for the PC a few years ago, for a 4:3 ratio 15" monitor it could have 4 dead pixels before it became enough of a problem to claim under warranty. Bear in mind the monitor size was 1,024 x 768 for a total of 786,432 pixels, so a few in 18 million isn't a major problem for the industry. Hopefully you can map them out with a manual clean anyway. I don't think I've ever suffered from the problem so far as I've not seen one on my photos, but I know my eyes aren't perfect close up so maybe it's just that I haven't seen one.


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spotz04
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Jun 24, 2012 11:12 |  #12

marzel wrote in post #14620708 (external link)
I was looking at some pictures I took last night and noticed that throughout the pictures, there were red noise dots in the EXACT same spots on all the pictures.

Is it possible to have deal pixels/photosites on the sensor thats causing it to show up red artifacts/noise throughout the image? Should this be expected? Can this be fixed? It does it mainly in low light, but also if I have medium room light at high ISO. I notice a specific set of red dots not moving when I scroll through my images on the computer. I know its the sensor because the red pixels are there regardless of where my camera is pointing.

Night shots, hm - did you do long exposures? If so then you'll get hot pixels, even on a brand new sensor, because this is normal.

Do a manual sensor cleaning with body cap on. In menu scroll to the yellow wrench with 2 dots, select Sensor cleaning > Clean manually > OK. Mirror will flip up. Leave in this mode 30-60 seconds. Power off camera, mirror will flip down. Turn camera back on, take a pic with the body cap on so you have a black pic, now check again for hot pixels.




  
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smorter
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Jun 24, 2012 11:38 |  #13

Normal, my 5D2 has like 20 of them :(

Try the body cap trick

The guaranteed way of getting rid of them is through a Canon CMOS recalibration. Free under warranty, otherwise costs about the same as a sensor clean.

And as others have said some software e.g. LR gets rid of it automatically


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spotz04
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Jun 24, 2012 12:05 as a reply to  @ smorter's post |  #14

I used the procedure on all three of my bodies after doing long (30 sec to 3+ min) exposures and it cleared up the hot pixels. Sometimes I had to run it twice, but not that often. The way I understand it, the procedure doesn't have power going to the sensor so if cleaning dust with a swab there's no static generated - when power is returned back to the sensor the pixels remap. If hot pixels don't clear up then, as "smorter" pointed out, send body into Canon for service.




  
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marzel
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Jun 24, 2012 13:04 as a reply to  @ spotz04's post |  #15

Thanks for the help guys! I'll give that a try!




  
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Dead Photosites?
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