Dead pixels

[modonlay]

I just got a Nikon Coolpix 4500. How can I test for dead pixels in the ccd?

[bobtrips]

Basically, take a picture in the dark and look for bright green spots.

You may find some that show up in extreme conditions. It's not a big deal, easy to clone them out. The big problem is when they show up in normal condition shots.

[modonlay]

I did the test and found 1. I can't see it in regular images. I expanded to 200% and still couldn't, see it - only on the black image. Is one bad pixel: bad, acceptable or good? How do you "clone out" a dead pixel?

[bobtrips]

Well, I don't take a lot of solid black shots so it wouldn't be very disturbing to me.

My Oly C2100z has one or two that show up in the darkest of shots that I take. (Wide open, 1/2 second exposure.) They don't bother me enough to bother sending the camera in to have them mapped out. *

When I'm editing the shot I just use the Clone Tool (I use Photoshop Elements), set the 'brush' to just a few pixels and 'clone' or copy a few pixels from a surrounding similar area and paste them over the bright green spot.

* Mapping is something that I'm sure happens with every digital before it gets shipped. There is an acceptable level of bad pixels/photo sites on a sensor and I'm sure that most of us wouldn't be willing to pay for a perfect sensor . The software is adjusted to ignore the reading from that photo site and use one next to it or an average of some around it. I don't know the particular algorithm used. Remember that it's one of two millions, four million, some millions of bits of information available.

[pwberndt]

You may want to go to YAHOO Groups http://groups.yahoo.com/ and join the coolpix990 group. There are several members and all Coolpix cameras are discussed. I believe that someone on the list has written software that can reprogram the camera to mask dead pixels. A couple of years ago I sent my 990 to Nikon and had it remapped to fix dead pixels. Since then, I haven't had any glaring problems.

[modonlay]

Thanks for the replies about dead pixels. I found only 1 and it isn't visible in normal images. I think I'll accept it gracefully.

[andreadyan]

What's a dead pixel?...

[bobtrips]

A dead pixel is a photo site on the sensor that for some reason isn't working. I think that every single camera has one or a few. (Maybe the Mars rovers don't, but NASA has THE deep pockets of photography.)

Camera go through a process during manufacturing in which the dead/non-responding pixels are detected and software corrections are made so that other data is substituted for the missing spot.

There may still be a couple of pixels that shut down in low light. (More accurately they aren't as light sensitive as desirable.) Or a pixel might die during the life of the camera. These will show up (at least with my camera) as bright, almost neon, green.

If dead pixels only show in the occasional shot, just clone them out. If they get to be a real problem you can generally send your camera in to the repair shop and have them 'mapped out', a re-run of what was done in the original manufacturing.

[andreadyan]

Ohh..Okay, thanks!

[texindian]

I don't disagree re: NASA's photo equipment today. But I couldn't help thinking of an interview I saw with members of the early moon crews. They literally went into a camera store and bought a Hasselblad with their own money so they could have some memorable pictures. How times change.

[bobtrips]

And, Boy!, was that a step forward.


Buck Rogers used a Kodak Brownie....

[physicalsystems]

I just got a Nikon Coolpix 4500. How can I test for dead pixels in the ccd?

Is seems that only Olympus E20 and E1 have menu selectable dead pixel mapping. I hope the Fuji S3 will have that. What's the big deal for the manufacturers to put this tiny function in there. My E20 had 1 additional dead pixel per month for the first half year in the FL climate. Now it is stable. But I read many angry complaints from people with professional digital cameras, costing thousands of dollars, with no dead pixel mapping built-in. They all had to send their cameras to the manufacturers service office to map out the dead pixels. Do the manufacturers just want us to buy new cameras all the time or do they want to drive us nuts?