Dark Frame Subtraction / Badpixel removal as in CHDK

[smilem]

Is it possible to have Dark Frame Subtraction?

"Controls the application of the Dark Frame Subtraction feature of your camera. Dark Frame Subtraction is a function used to reduce the effects of sensor noise - especially useful when exposure times are 1.3 seconds or longer.  When dark frame subtraction is enabled,  the camera essentially takes two pictures with the same exposure time - once with the shutter open and then again with the shutter closed.  By subtracting the second frame's pixel values from the first frame's,  the camera automatically removes most sensor thermal noise from the image."

http://chdk.wikia.com/wiki/CHDK_1.2.0_User_Manual

Badpixel removal
http://chdk.wikia.com/wiki/Badpixel_removal

To remove defective pixels in an image in CHDK, there is the Bad pixel removal feature. Once a list containing all the bad pixels for your camera has been generated, CHDK can remove them automatically. The file with the badpixel data is named badpixel

[dmilligan]

Your camera can already do this. It's in the custom functions in the canon menu. Enable 'Long Exposure Noise Reduction'

I prefer to shoot only a few dark frames and calibrate in post, since if you enable this it doubles the amount of time for each exposure you take.  You can also get better dark frame calibration results by taking multiple dark frames and stacking them, then using the 'master' dark for calibration (same goes for bias). Since bias never really changes I simply have a bias master that I use for each camera.

[smilem]

Could you be more specific as I don't have the camera yet, I'm looking to buy it if fits my needs.
How can you shoot dark frames and calibrate in post? How does it compare to in camera mode?

I'm going to shoot for long periods of time (24hrs) continous, I want to remove hot pixels, dead pixels, etc.
CHDK works ok for me on canon sx110is, but that camera is getting too old I decided to upgrade and use custom lens too.

[dmilligan]

How can you shoot dark frames and calibrate in post? How does it compare to in camera mode?

There are a number of programs that do this (pretty much any astrophotography processing software worth it's salt), it's really just simple subtraction. Doing calibration in post is far superior to in camera for a number of reasons. The main one being the one I mentioned, that you don't loose half your time to taking dark frames. Also you can get a little better calibration results by stacking several dark frames together (this averages out the random noise signatures present in your dark frames and leaves you with only the thermal noise, hot/cold pixel signature).

The main caveat to this process is that it must be done before debayering takes place. So you have to shoot in RAW (which, why would you ever not?). And the software you use must apply the calibration before it does debayering (in other words, you can't simply use photoshop to subtract the two layers).

I use PixInsight for this (but it is very advanced and has a steep learning curve, it's also not free), but there are free programs out there that can do this (I know Deep Sky Stacker can, but I've never used it, its Windows only)

[Joachim Buambeki]

Is it possible to have Dark Frame Subtraction?

There is a programm called Pixelfixer that should be able to do what you are asking for.