How to force a script/CHDK to subtract dark frames?

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How to force a script/CHDK to subtract dark frames?
« on: 04 / September / 2013, 21:57:50 »
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I'm using a script timelapsebc.lua and CHDK from 2011 on Canon SX130. Most of the time dark subtraction works and takes the same time as the photo itself. But sometimes I shoot like a ~2 minute exposure and there's no dark frame being taken or a very short one like half a second. Then I end up with a bunch of garbage pixels. It just happened to me again, I suspect it happens because it's the beginning of another month and the camera creates a new directory for each month.

After creating another badpixel.bin (which didn't help) and messing with different modes, shooting with a script and without, restarting many times with and without CHDK I got dark frames back, but I've no idea what did it.

Re: How to force a script/CHDK to subtract dark frames?
« Reply #1 on: 04 / September / 2013, 22:25:18 »
Darkframe subtraction is done by the Canon firmware - not CHDK.   You can disable darkframe subtraction with CHDK but other than that, its up to your camera.

If you are still running a two year old version of CHDK, I'd suggest an update to that regardless.  A lot has happened in the last two years.
Ported :   A1200    SD940   G10    Powershot N    G16

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Offline reyalp

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Re: How to force a script/CHDK to subtract dark frames?
« Reply #2 on: 04 / September / 2013, 22:33:44 »
Not sure I can help, but I can tell you some things it's not
- badpixel.bin is completely unrelated
- Folders on the card and months should be irrelevant, although it isn't totally impossible
- CHDK doesn't (intentionally) change how long the dark frame is. We don't even know how to do that if we wanted. It's possible that messing with the exposure propcases while the shot was in progress would do it.
- The control CHDK has over dark frame is in only the on/off/auto described in http://chdk.wikia.com/wiki/CHDK_scripting#set_raw_nr

If you can post the actual script you are using as an attachment, that might help us.
Don't forget what the H stands for.

Re: How to force a script/CHDK to subtract dark frames?
« Reply #3 on: 05 / September / 2013, 12:35:17 »
Here's the script.


 

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