I would like to figure out if magic lantern can give me an evaluation of noise in my images. Particularly with astrophotography, if I can figure out the Read e- noise value in an individual image, I can make a rough estimate of how many subs I will need to shoot for integration and also how long of an exposure I need to take in order to swamp the read noise. This of course would need to be a reading from the raw file and not the jpeg preview and it would need to give a value listed in the R,G,B channels independently. Cutting out the need for a computer for this process would be huge.
It can - try the raw_diag module.
There are a couple of methods:
- from OB areas (not reliable, just an extremely rough approximation, but works on any image)
- from one dark frame (includes both fixed and random components)
- from the difference of two dark frames (you'll get the random noise component * sqrt(2), assuming it's Gaussian)
- from the difference of two regular images (http://www.magiclantern.fm/forum/index.php?topic=10111.msg117955#msg117955) (so you can estimate the noise at various signal levels - enough information for plotting a SNR curve).
I have some trust in the last method, especially for DR measurements, as long as white level (clipping point) is autodetected well (sometimes it isn't (http://www.magiclantern.fm/forum/index.php?topic=20579)). However, fitting FWC and read noise from the SNR curve is probably an ill-conditioned problem - if you can suggest a better method, I'm all ears.
Quote from: a1ex on September 27, 2017, 06:04:37 PM
It can - try the raw_diag module.
There are a couple of methods:
- from OB areas (not reliable, just an extremely rough approximation, but works on any image)
- from one dark frame (includes both fixed and random components)
- from the difference of two dark frames (you'll get the random noise component * sqrt(2), assuming it's Gaussian)
- from the difference of two regular images (http://www.magiclantern.fm/forum/index.php?topic=10111.msg117955#msg117955) (so you can estimate the noise at various signal levels - enough information for plotting a SNR curve).
I have some trust in the last method, especially for DR measurements, as long as white level (clipping point) is autodetected well (sometimes it isn't (http://www.magiclantern.fm/forum/index.php?topic=20579)). However, fitting FWC and read noise from the SNR curve is probably an ill-conditioned problem - if you can suggest a better method, I'm all ears.
Alex, this sounds awesome. I will need to check this out later on and see what I can explore the feature more