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10-29-2007, 06:56 PM   #1
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Hot Pixels disappearing???

I recently went on a trip and took lots of photos. I notice there are some hot pixels in the same spots on a lot of them, regardless of day or night shots. Luckily I could only see a few. However, when I took some shots with the lens cap on and ran the dead pixel software I found on this forum, there was NONE! I took 1 0.5" pic for each ISO without SR, and repeat for SR for a total of 10 shots. None of them have a single stuborn pixel. Then I randomly took a few pics in a room with lights off, I can't spot any bright pixels. Does this make any sense?

One silly point: I live in Toronto, Canada. And this is where I am doing the test. The trip I took was in Italy & Greece, quite a bit warmer than here. Does HOT pixel have anything to do with "HOT" temperature? i know this may sound dumb, but I really can't think of other explanation.

Thanks in advance.

10-29-2007, 06:59 PM   #2
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For several days last month, I had one annoying red pixel that showed up in all my night shots. Just when I noticed it and started to get annoyed by it, it disappeared.

So yes...sometimes hot pixels don't stay hot.
10-30-2007, 01:12 AM   #3
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QuoteOriginally posted by SimSV Quote
I recently went on a trip and took lots of photos. I notice there are some hot pixels in the same spots on a lot of them, regardless of day or night shots. Luckily I could only see a few. However, when I took some shots with the lens cap on and ran the dead pixel software I found on this forum, there was NONE! I took 1 0.5" pic for each ISO without SR, and repeat for SR for a total of 10 shots. None of them have a single stuborn pixel. Then I randomly took a few pics in a room with lights off, I can't spot any bright pixels. Does this make any sense?

One silly point: I live in Toronto, Canada. And this is where I am doing the test. The trip I took was in Italy & Greece, quite a bit warmer than here. Does HOT pixel have anything to do with "HOT" temperature? i know this may sound dumb, but I really can't think of other explanation.

Thanks in advance.
Hi, I cannot locate the dead pixel software you are referring to.
Can you show the link pls?

- Bert
10-30-2007, 04:22 AM   #4
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QuoteOriginally posted by bymy141 Quote
Hi, I cannot locate the dead pixel software you are referring to.
Can you show the link pls?

- Bert
StarZen Technologies, Inc; DataFlex tools and books

10-30-2007, 05:14 AM   #5
baw
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Re: Hot Pixels

QuoteOriginally posted by SimSV Quote
One silly point: I live in Toronto, Canada. And this is where I am doing the test. The trip I took was in Italy & Greece, quite a bit warmer than here. Does HOT pixel have anything to do with "HOT" temperature? i know this may sound dumb, but I really can't think of other explanation.
No so silly at all. I did quite some hot pixel remapping with my Nikon CP5700.
I did cool the camera before remapping and I got less hot pixels then when the camera was at room temp. Leaving the cam on for some time created also more hot pixels.
(5700 has live view, so the sensor is on all the time.)

Another possibilty is Noise Reduction. When ON with longer exposures the cam takes a second exposure with shutter closed to find the hot pixels. These are then "removed" from the original exposure.

I don't understand why the camera manufacturers don't supply the remapping software with the camera. It's a very simple and fast procedure.
10-30-2007, 08:21 AM   #6
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Thanks!

- Bert
10-30-2007, 11:55 AM   #7
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Adobe's ACR (in Photoshop and Lightroom) automatically removes hot/stuck/dead pixels in photos.
10-30-2007, 04:43 PM   #8
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QuoteOriginally posted by baw Quote
I don't understand why the camera manufacturers don't supply the remapping software with the camera. It's a very simple and fast procedure.
I read that the Canon 40D (don't know about others) comes with such software, so maybe the others will follow.

10-31-2007, 01:30 AM   #9
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Re: Hot pixel remapping.

QuoteOriginally posted by Arpe Quote
I read that the Canon 40D (don't know about others) comes with such software, so maybe the others will follow.
That would be kind of a breaktrough. Do you have a link, I did check the review on DPR, but couldn't find anything.
10-31-2007, 04:21 PM   #10
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Sorry, can't find it again!
10-31-2007, 05:27 PM   #11
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QuoteOriginally posted by baw Quote
That would be kind of a breaktrough. Do you have a link, I did check the review on DPR, but couldn't find anything.
Actually not that new.
Aug 17 2001
............
"Automatic Pixel Mapping" (APM). APM was developed to keep the camera operational over an extended period of time reducing the need to send the camera in for service by Olympus. APM is simple to use - all you have to do is go to the camera menu when the C-4040 Zoom is first turned on, and set the menu to pixel mapping, then go to start, and hit the OK button. The CCD re-mapping begins, taking about 10 seconds to complete.
......................
Actually this should be required reading for ALL new digital camera owners, especially the pixel-anal ones.
NEWS! - Olympus discusses 'Auto Pixel Mapping'!
AND if I remeber correctly someone else does this (re-mapping) automatically on a cleaning cycle. May be Olympus on their DSLR's
11-01-2007, 01:01 AM   #12
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Re: Hot pixel remapping.

Hi Jeff

Thanks for the info. I knew about non-dslr's having this capabilty. For some it's embedded in the firmware. My Nikon CP5700 has it in the firmware, only Nikon never made software available to use it. Some clever guy created a hack.

Afaik no dslr has this option yet, so the 40D having it would be interesting.
I suspect Pentax has something in the firmware as well. Noise Reduction does most of the job already, you only have to save and use the "map"with the hot pixels.
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