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what does dead pixel look like
I bought a DSLR last week. when I take a picutre for 30seconds, iso1600 with the lens cap on, I found some red, blue and green dots. are they dead pixel in the sensor?.

There is the red one. 100%crop.

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Comments (12)

If you think that makes sense, then you must have read someone else's post!..

Comment #1

Fraid so. One I could probably tolerate, but if you have several, and it's a new camera, I'd take it back.Androohttp://Androo.smugmug.com..

Comment #2

Dead pixels appear to be black since they do not register any light energy. What you have appears to be hot pixels (sometimes called "stuck pixels"). However, you did take this photo in an "extreme" test - long exposure, high ISO, with lens cap on. If these are truly "hot pixels" you should be able to repeat this a number of times and and the same pixels would show as a problem. Your image could also be a result of camera noise in this extreme test..

My suggestion is that you post your question on the Pentax forum - I assume you have a Pentax? Those folks are likely to be much more familiar with your camera model and any hot pixel issues or fixes..

Good luck ....

- Simon.

Http://scpics.smugmug.com/..

Comment #3

This is hot pixel..

They are inevidable at ISO 1600 and long exposure...

Try same test with ISO 100, 1, 4, 10 30 sec exposures and digital noise reduction function disabled..

Http://www.stan-pustylnik.smugmug.com..

Comment #4

So they are normal and I can't do anything about it?..

Comment #5

New_type wrote:.

So they are normal.

Yes, they are normal. Only if there are lots that show up in normal shooting would you have cause for complaint..

And I can't do anything about it?.

Some cameras map them at out at intervals, usually monthly... but I don't know if yours is one of those.Regards,Baz..

Comment #6

I could be wrong,but I think the Pentax K200D supports pixel mapping?.

That's your answer I'm thinking...

Comment #7

What do you mean map them out? to eliminate it?.

Barrie Davis wrote:.

New_type wrote:.

So they are normal.

Yes, they are normal. Only if there are lots that show up in normalshooting would you have cause for complaint..

And I can't do anything about it?.

Some cameras map them at out at intervals, usually monthly... but Idon't know if yours is one of those.Regards,Baz..

Comment #8

I see that you "sort of" took my suggestion of posting your question on the Pentax forum. However, you posted in an already existing thread that is very full. This makes it very difficult for Pentax forum members to find your question and give you advice/info. I suggest that you post your possible hot pixel image as a NEW thread on the Pentax forum. One more suggestion, before you post, you probably should do a quick search to see if your question as already been answered for your specific camera model..

Good luck ....

- Simon.

Http://scpics.smugmug.com/..

Comment #9

These are hot pixels.They typically show up in long exposures.They are perfectly normal !!! There is nothing wrong with your camera!.

What you want to do is to save the dark frame that you just took at 30 seconds..

Every 30 second picture that you take with the lens cap off will have the same hot pixels. So what you want to do is subtract the dark frame (with the lens cap on) from the 30 second picture and thus eliminating the hot pixels from the picture. Some photomanglers make this easy to do.....others not so much..

Typically you want to take a dark frame exposure of the same number of seconds as any long exposure at the time of the long exposure. You'll only need one dark frame for any series of exposures. The reason to take it at the time is that the number of hot pixels that show up is related to how long the camera has been on and the temperature of the environment. On a cold night you'll get a lot fewer hot pixels than on a hot summer night..

Clear as mud?A member of the rabble in good standing..

Comment #10

New_type wrote:.

What do you mean map them out? to eliminate it?.

Yes..

The mapping makes a note of the coordinates of the hot pixel, and substitutes a set of RGB values for that pixel that is similar to those from adjacent pixels.... and continues to do that for every shot thereafter..

Is your camera the K20D? If so, I found this after entering "mapping out hot pixels" into Google....

Http://pentaxlife.com/pentax-k20d-hot-pixels-problem-confirmed.

I hope this is helpful.Regards,Baz..

Comment #11

... like a live one, but lying on it's back with it's feet in the air?Mike..

Comment #12

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This question was taken from a support group/message board and re-posted here so others can learn from it.

 

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