Dead CCD pixels

[lamont]

In a former life I was an physics/astronomy double major and learned how to use liquid nitrogen-cooled CCD detectors in ~2-3m telescopes. So I learned an awful lot about the care and feeding of CCD detectors and a lot of stuff that can go wrong with them including dead pixels, and it looks like my c-5050 has a dead pixel:

Kind of a really bad picture, but near the diver's right knee you can clearly see a streak due to a dead pixel which is now showing up in all my pictures apparently. I haven't dug into the warantee situation, but I'm pretty sure this camera is at least 2 years old so I'm dubious that its still waranteed (and its not made by olympus anymore). Does this mean that the camera is now my backup and I should buy another one, or can I get this fixed? Anyone else have this issue before and know what to do about it?

 

[alcina]

You can see if they will fix it...it might be something simple. I had a similar problem with a video rig and it only cost like $60 to get it dealt with. Worth it to ask.

For me, if it couldn't be fixed, that camera would go in the bin or I'd donate it. I wouldn't use it because I would never be happy with the results and ruined images wouldn't be worth the monetary savings of buying something else.

YMMV and I adore shopping

 

[SeaYoda]

Did you ever check into the CCD recall on the 5050? Was your serial number one of the affected CCDs - mine was. The problem was supposed to look different than yours, but mine had a couple dead pixels and didn't look anything like what they were showing examples of either. They replaced my CCD for free so it's worth giving them a call. If you do get to send it back, don't send it to New York. They did a bad job on mine and gave me attitude to top it off (I sent it to California the second time to get it fixed for good).

 

[kapula]

I've had that problem with my c-8080. It is known to have some hot pixels. You can't really tell them from normal shot but if you take a shot in complete darkness (with lens cover on for example) and expose it full 15secs you could see few hot red pixelgroups (4 pixels/group).

Oh actually now that I recall how it went I did have pretty similar problem with some lines going just like on your ccd. I had many more lines though. You could see them very well in u/w pictures with blue background. I sent a picture to olympus and they asked me to bring my camera to service. I still had warranty but that kind of a proplem should (at least in my case it was a faulty ccd) be under warranty eventhough the time period is over. Anyway I brought it to a local oly service point and they shipped it to Spain and I got it back 2 weeks later with a new ccd.

 

[victor]

My 2c worth,
I don't think a dead pixel will give you a line, I thought it would give you a dot.
A line sounds more like a memory addressing problem or a buffer issue.
Looking at the picture the line does not look like it is vertical, but at a slight angle.
That makes me think its not from the ccd. I suspect the ccd is addressed the same way as memory, if it was an addressing problem then the line would go right across the picture at right angles.

I am sure if you can find a tecky who is interested in the problem it can be fixed, maybe not economically for a land camera but if you have to buy a whole new setup it may be worth the cost.

I wish you luck, and keep us informed

 

[kapula]

Victor:
I had many lines on my faulty ccd. The dead pixels I had weren't visible in normal pictures but only in black shots. So faulty ccd could still be the case here. You propably should send the pic to oly service and ask their opinion.

 

[lamont]

My 2c worth,
I don't think a dead pixel will give you a line, I thought it would give you a dot.
A line sounds more like a memory addressing problem or a buffer issue.
Looking at the picture the line does not look like it is vertical, but at a slight angle.
That makes me think its not from the ccd. I suspect the ccd is addressed the same way as memory, if it was an addressing problem then the line would go right across the picture at right angles.

I am sure if you can find a tecky who is interested in the problem it can be fixed, maybe not economically for a land camera but if you have to buy a whole new setup it may be worth the cost.

I wish you luck, and keep us informed

CCDs are not addressed like memory. They're read out via bit-bucket to a single ADC. The first scan line at the top is read out pixel-by-pixel shifting right or left (i can't recall offhand which way, i think right) onto the ADC, then the data in each pixel is moved up to the pixel above it. Wash, rinse, repeat until the entire picture is read out (and since that means that the lower left hand corner is shifted by pixel_height + pixel_width times which is a few thousand times at least that means that the copying fidelity of shifting data from pixel-to-pixel has to be extremely high -- although you can measure the noise in the image and you'll see that the lower left corner is noisier then the upper-right).

The dead pixel in this case is one that breaks the bit-bucketing, so all the pixels below it get shifted up until they hit that pixel and then their information gets wiped out, so you get a streak down the picture. I've got over a hundred pictures from my mexico trip and flipping through them that line is in exactly the same place in every single one of them. I'm positive this is a fried pixel on the CCD (the CCD we used to take pictures of Messier 15 when I was an undergrad had a ton of fried pixels like this in one corner and you just needed to shoot your image around them).

Thanks everyone for the help, though. This isn't the problem involved in the recall and I haven't been able to figure out if my camera is part of the recall or not, or where I might get it serviced, but I've got an idea of what to do now...

 

[victor]

Lamont
Let me see if I understand the CCD.
So the CCD is essentially a serial device.
It empties one line into the analogue to digital converter bit by bit.
Then it pushes the whole picture up one line and repeats the process.
So if the damage is in the process that is involved in push process you get a line down the picture from the damaged pixel.
Other faults are only in the recording process so you can get a hot spot or a black spot.
Seems like you would have to go to an enormous amount of trouble to avoid cumulative distortion as you replicate analogue data many times.

Does a CMOS sensor behave the way I thought?

 

[lamont]

Seems like you would have to go to an enormous amount of trouble to avoid cumulative distortion as you replicate analogue data many times.

Yes, the efficiencies of transferring charge from one pixel to another are extremely high. That process of moving charge across a semiconductor was what was actually invented first and using the photoelectric effect to deposit charge into the bits was added in order to create CCD cameras.

Does a CMOS sensor behave the way I thought?

From wikipedia it looks like CMOS sensors are more like what you were describing. The ADC is in each pixel and you can read out a line at a time. I didn't do enough research to figure out if the lines are addressable or not...