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Powershot SX240 hot spot issue

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Offline Aclys

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Powershot SX240 hot spot issue
« on: 04 / March / 2013, 18:28:03 »
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Hello!

I've got a Canon Powershot SX240 and after about 7 minutes of video capturing there will be plenty of white spots ("hot pixels") on each video. I tried to create a badpixel.bin, but this didn't work out. Does anyone have an advice for me?
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Offline lapser

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Re: Powershot SX240 hot spot issue
« Reply #1 on: 04 / March / 2013, 19:36:52 »
Quote from: Aclys on 04 / March / 2013, 18:28:03
I've got a Canon Powershot SX240 and after about 7 minutes of video capturing there will be plenty of white spots ("hot pixels") on each video.
Try displaying the CMOS temperature. Go to the alt main menu/CHDK/OSD/Show Temperature/ and set to "CMOS". See how high it goes while recording a long video.

I haven't done much video with my SX260 (same camera with GPS), but the only thing I can think of to try is to make sure the ISO is set to 100, and you have the ISO override in the CHDK Enhanced Photo  menu OFF.
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EOS-M3_120f / SX50_100b / SX260_101a / G1X_100g / D20_100b
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Offline waterwingz

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Re: Powershot SX240 hot spot issue
« Reply #2 on: 04 / March / 2013, 21:12:00 »
Quote from: Aclys on 04 / March / 2013, 18:28:03
I've got a Canon Powershot SX240 and after about 7 minutes of video capturing there will be plenty of white spots ("hot pixels") on each video. I tried to create a badpixel.bin, but this didn't work out. Does anyone have an advice for me?
Do the hot pixels start off small and dim and then grow?   Or do the just appear suddenly in one frame ?
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Ported :   A1200    SD940   G10    Powershot N    G16
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Offline reyalp

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Re: Powershot SX240 hot spot issue
« Reply #3 on: 04 / March / 2013, 22:26:50 »
Quote from: Aclys on 04 / March / 2013, 18:28:03
I've got a Canon Powershot SX240 and after about 7 minutes of video capturing there will be plenty of white spots ("hot pixels") on each video. I tried to create a badpixel.bin, but this didn't work out. Does anyone have an advice for me?
badpixel.bin is only used to handle pixels already known bad by the firmware in dng. The other CHDK badpixel system can be used to patch arbitrary pixels, but only for still images. Neither will do anything at all for video.
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Offline Aclys

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Re: Powershot SX240 hot spot issue
« Reply #4 on: 05 / March / 2013, 07:29:39 »
I tried to change the ISO to 100, but i did not find this option in video mode (there it is always "iso auto"). I made a test capturing over about an hour. the cmos-temperature was about 55 °C (131 °F) at maximum.

the hot pixels occur suddently after 7 minutes (before, none is seen), then over time some more pixels grow. (from dark grey to almost white).
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Offline waterwingz

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Re: Powershot SX240 hot spot issue
« Reply #5 on: 05 / March / 2013, 08:48:57 »
Quote from: Aclys on 05 / March / 2013, 07:29:39
the hot pixels occur suddently after 7 minutes (before, none is seen), then over time some more pixels grow. (from dark grey to almost white).
Well then,  its seems there are two possabilities.

First off,  you may have a hardware problem with your camera.  A marginal sensor or a sensor not mounted with good heat sink contact perhaps.   I guess we will not know if this a problem with the camera until others have reported the same result - or not getting the same result.

Alternatively,  its possible you have discovered why Canon limits the time duration in certain video modes.  Where you shooting in one of the HD modes?  Does CHDK allow you to shoot longer in that mode than CHDK does?  What happen after 7 minutes when you are shooting in one of the lower resolution modes?  Do you see the same thing when  CHDK is not loaded?

Either way,  its does not seem to be something CHDK is doing - or anything CHDK can prevent.


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Ported :   A1200    SD940   G10    Powershot N    G16
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Offline lapser

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Re: Powershot SX240 hot spot issue
« Reply #6 on: 05 / March / 2013, 11:19:05 »
Quote from: Aclys on 05 / March / 2013, 07:29:39
I tried to change the ISO to 100, but i did not find this option in video mode (there it is always "iso auto"). I made a test capturing over about an hour. the cmos-temperature was about 55 °C (131 °F) at maximum.
What kind of video are you making? Is it a low light scene? The lower the light level, the higher the ISO will be set, and the more noise you'll get.

The temperature seems within the normal range. That is, it won't damage the sensor, but it will increase the noise. My sx260 isn't a very good low light camera, and shows a lot of hot pixels with long exposures at night. If you're doing a low light scene, this may be the best the camera can do.
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EOS-M3_120f / SX50_100b / SX260_101a / G1X_100g / D20_100b
https://www.youtube.com/user/DrLapser/videos
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Offline Aclys

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Re: Powershot SX240 hot spot issue
« Reply #7 on: 08 / March / 2013, 14:58:46 »
Thx for all the answers :) I will do some more tests with lower resolutions and so on when i have more time than right now. in the past i just shot full-hd videos with pretty dark lighting conditions.
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Offline Caefix

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Re: Powershot SX240 hot spot issue
« Reply #8 on: 26 / May / 2022, 15:21:38 »
Quote from: lapser on 05 / March / 2013, 11:19:05
Is it a low light scene? The lower the light level, the higher the ISO will be set, and the more noise you'll get.  :o
... this may be the best the camera can do.
... "Filmed with a Canon SX260 HS."
Maybe sound recording, too? It´s also a good example for digital distortion, breaking the 0dB sound barrier.  ;)
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