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Bad pixel count for SX1

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Offline sithspawn

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Bad pixel count for SX1
« on: 07 / July / 2009, 10:07:30 »
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I've got a SX1 that reports 94,576 bad pixels using the default badpixel-script. I think it's quite high; but if it is my cameras sensor or if it's due to CHDK with this CMOS-sensor - I don't know.

Since the badpixel-list is used for RAW (dng) processing from what I understand, I think it could cause problems in the case that the badpixels are wrongly reported by CHDK. (If it is not, my sensor's on the fritz in my book.)

For reference, might I ask other SX1 users to try badpixels and report?

EDIT: I've since discovered that I sometimes get 94,576, and sometimes something like 43,000. Note I turn the cam on/off to have different results, otherwise identical conditions.

TIA,

 Pez
« Last Edit: 08 / July / 2009, 07:12:41 by sithspawn »
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Offline MRQ

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Re: Bad pixel count for SX1
« Reply #1 on: 07 / July / 2009, 20:56:39 »
87764, first run ever with lens cap on and I got exact same numbers with cap off.
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Offline sithspawn

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Re: Bad pixel count for SX1
« Reply #2 on: 08 / July / 2009, 07:14:38 »
Quote from: MRQ on 07 / July / 2009, 20:56:39
87764, first run ever with lens cap on and I got exact same numbers with cap off.

Do you have the same number even if you turn the camera on/off a few times and run it again? My cam changes even though its only seconds apart.
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Offline fe50

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  • IXUS50 & 860, SX10 Star WARs-Star RAWs
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Re: Bad pixel count for SX1
« Reply #3 on: 08 / July / 2009, 07:44:08 »
Some Powershots has two or more internal bad pixel lists, so dependent from the choosen settings (like exposure, ISO or others) the amount of reported bad pixels may vary.

Nonetheless the bad pixel count ougth to be always the same under identical circumstances...
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Offline MRQ

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Re: Bad pixel count for SX1
« Reply #4 on: 12 / July / 2009, 08:09:24 »
Did some more tests today, only tried different ISO's and I didn't have time to go through all the settings.
Here is what I found.

P :                                   Tv:                                 Av:                              M:
ISO80     = 39785           ISO80    = 39785           ISO80     = 39785       ISO80     = 39785

ISO400   = 87764           ISO400   = 87764           ISO400  = 87764        ISO400   = 87764

ISO1600 = 98490           ISO1600 = 98490           ISO1600 = 98490        ISO1600 = 98490

(ISO Hi   =  92537, only available in P)



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Offline fe50

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Re: Bad pixel count for SX1
« Reply #5 on: 12 / July / 2009, 09:06:10 »
Quote from: MRQ on 12 / July / 2009, 08:09:24
Did some more tests today, only tried different ISO's and I didn't have time to go through all the settings.
Here is what I found.
P :                                   Tv:                                 Av:                              M:
ISO80     = 39785           ISO80    = 39785           ISO80     = 39785       ISO80     = 39785
ISO400   = 87764           ISO400   = 87764           ISO400  = 87764        ISO400   = 87764
ISO1600 = 98490           ISO1600 = 98490           ISO1600 = 98490        ISO1600 = 98490
(ISO Hi   =  92537, only available in P)

Looks plausible to me, seems like the SX1 uses 3 internal lists.
The badpixel.lua script executes set_tv96_direct(96) first, which sets Tv to 0.5 seconds - so different Tv settings you set up won't be used - Tv will be always be 0.5 seconds.
The HiISO mode is not a fixed ISO setting, the camera selects ISO automatically, e.g. ISO800; also the IS=3200(Scene) mode on newer Powershots is somewhat special...
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Offline sithspawn

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Re: Bad pixel count for SX1
« Reply #6 on: 15 / July / 2009, 13:52:08 »
I've tried every possible combo now; three lists it is - only my cam sometimes seem to get it wrong? On occation it seems like my second list is used over the first list, but it isn't as common now. Could it somehow be temperature related, that the sensor automagically adjusts? It occured more frequently last time I checked (and the temp was well above 30C, now it's a mere 22C).

(My lists are 43311, 94956 and 106056 at 80/400/1600 - but occasionally 94956 occurs in ISO 80 as well)

Needless to say, this is the first time I ever care about the inner workings of any camera even though I've been known to program Atmel AVR and fiddle with the old soldering iron - but this is new territory :)

EDIT: I can answer myself: yes, they are sensitive to temperature, dumbass ;)
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