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Old May 19, 2006, 12:02 PM   #21
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maxxum7d

Were these (hot pixels) only occuring on longer exposures, or were they occuring on all exposures, regardless of shutter speed?

If only on longer exposures, turn on your noise reduction. It uses a dark frame subtraction system to map them out, and will have no impact on shorter exposures.

If it's on all exposures, regardless of shutter speed, the camera can check for them (although it sounds like you've already replaced it).

If you run into the problem again, there is an undocumented feature in the KM DSLR models to map out bad pixels (it checks for them automatically once per month).

To force it, set your camera's date and time up to the last few minutes of the last day in the month.

Turn it off, and wait until enough time has passed for the internal clock to change months. Turn the camera back on, wait a few minutes to make sure it's peformed a remap, then take some photos and make sure the bad pixels are gone. Then, reset your date and time so it's correct.

It's probably best to do it with a warm camera to make sure it finds them all (the warmer the sensor, the more likely they'll occur).

Be glad you've got a KM DSLR. With most other brands, if the factory missed any of them when the bad pixel table in EEPROM was updated (or the camera developed bad ones later), you'd need to send it in to the manufacturer to have it done (they have service software that checks for them and updates a table in EEPROM).

There are some exceptions. For example, a number of newer Olympus models have a menu choice for mapping them out. I've got software that maps them out for a Nikon D100; and I've also got some software that maps them out for some of the early Olympus and Nikon non-DSLR models.

But, the manufacturers don't like to give users the service software to do it themselves (most probalby don't want users to even know that sensors have defects and there is a bad pixel table the camera looks at, replacing bad pixels with values interpolated from adjacent pixels).

Here is a recent thread where I go into more detail on hot pixels, etc (a D100 owner had a problem and I pointed him to software to update his camera's bad pixel table in EEPROM). With your KM DSLR, you don't even need software to fix them.

http://www.stevesforums.com/forums/v...mp;forum_id=58


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Old May 19, 2006, 12:18 PM   #22
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Oh they occured on all exposures. Same spot over and over again. Finally I closed the lens lid and took a shot of the darkness and I could almost see a cloudy night sky! There were little spots all over the place which I could see using the built in zoom. Yes, I had it replaced but Adorama is creeping me out now. The salesmen seem manipulative. I am more used to shopping at chain stores like Circuit City and Best Buy where you can remain anonymous and return items if they are defective without any problems. At Adorama, they recognize you and use all kinds of car salesman tricks.

Thanks for the information on the undocumented feature. I'll keep it in mind in case I run into the same problem again. Are these bad pixels a software bug or something to with the CCD physically?

JimC wrote:
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maxxum7d

Were these (hot pixels) only occuring on longer exposures, or were they occuring on all exposures, regardless of shutter speed?

If only on longer exposures, turn on your noise reduction. It uses a dark frame subtraction system to map them out, and will have no impact on shorter exposures.

If it's on all exposures, regardless of shutter speed, the camera can check for them (although it sounds like you've already replaced it).

If you run into the problem again, there is an undocumented feature in the KM DSLR models to map out bad pixels (it checks for them automatically once per month).

To force it, set your camera's date and time up to the last few minutes of the last day in the month.

Turn it off, and wait until enough time has passed for the internal clock to change months. Turn the camera back on, wait a few minutes to make sure it's peformed a remap, then take some photos and make sure the bad pixels are gone. Then, reset your date and time so it's correct.

It's probably best to do it with a warm camera to make sure it finds them all (the warmer the sensor, the more likely they'll occur).

Be glad you've got a KM DSLR. With most other brands, if the factory missed any of them when the bad pixel table in EEPROM was updated (or the camera developed bad ones later), you'd need to send it in to the manufacturer to have it done (they have service software that checks for them and updates a table in EEPROM).

There are some exceptions. For example, a number of newer Olympus models have a menu choice for mapping them out. I've got software that maps them out for a Nikon D100; and I've also got some software that maps them out for some of the early Olympus and Nikon non-DSLR models.

But, the manufacturers don't like to give users the service software to do it themselves (most probalby don't want users to even know that sensors have defects and there is a bad pixel table the camera looks at, replacing bad pixels with values interpolated from adjacent pixels).

Here is a recent thread where I go into more detail on hot pixels, etc (a D100 owner had a problem and I pointed him to software to update his camera's bad pixel table in EEPROM). With your KM DSLR, you don't even need software to fix them.

http://www.stevesforums.com/forums/v...mp;forum_id=58

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Old May 19, 2006, 12:31 PM   #23
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It's the sensor (CCD) itself.

Hot pixels are when photosites record a higher value (brighter) than they should, usually with longer shutter speeds. When the problem occurs at faster shutter speeds, too, they're considered "stuck" (always bright).

Virtually all CCDs will have them in some conditions. The longer the shutter is open, (and the darker the conditions since not enough photons are hitting the sensor) the more likely a photosite won't be linear in it's output when responding to light, and it will record a higher value than it should.

Temperature also impacts it (which is why you see cooling systems for sensors in digital cameras used in astronomy).

You just don't see hot pixels with most newer cameras because of built in noise reduction to subtract them out on longer exposures, since the ones that occur at typical shutter speeds have already been mapped out at the factory.

With many older cameras, there is no dark frame subtraction system (but, many do have a bad pixel table in EEPROM that contains a list of known bad pixels when the camera shipped from the manufacturer).

Unfortunately, sometimes with age, a CCD develops more bad pixels (ones that are not linear in the way they respond to light at typical shutter speeds). Sometimes they're too bright (hot), and sometimes they don't respond at all (dead).

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Old May 20, 2006, 12:07 AM   #24
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Hi Maxxum7D!

I'm really surprised!!!!

Friends, buy cameras & other photo items from Adorama main store in NY...they shipped the items to Israel with no problems, at all, from the buyers!

Try directly from the Main/principal store...I hope for you that all will be at the very best solution!:-D

Cheers,

Alex 007:|
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Old May 20, 2006, 11:20 AM   #25
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maxxum7d wrote:
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Update: the new camera that Adorama gave me has multiple hot pixels. When I took this one back, the salesman started bitching initially and wanted to exchange without doing any paperwork. This was a somewhat disappointing experience. I got a new body but I don't plan on shopping at Adorama anytime soon. They are like a family owned cellphone shop, and only want to sell.
Well at least they did exchange it. I am surprised that they wanted toexchange without paperwork, though I'm not sure how exchanging without paperwork would make a difference. Good luck with your new one.


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Old Jun 6, 2006, 3:24 PM   #26
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The new camera I got after the exchange comes with 3 hot pixels for all ISOs shot with 1/8th of a second or longer. After reading this thread I decided to give up on CCD perfection. This is with noise reduction on. I am eagerly waiting for a future 7D based super camera by Sony!
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