Difference between revisions of "Noise Reduction"
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Record sensor temp alongside raw, apply different noise compensation depending on temp in post. | Record sensor temp alongside raw, apply different noise compensation depending on temp in post. | ||
A Peltier can help build the profiles - by heating and cooling to a range of temperatures as needed. | A Peltier can help build the profiles - by heating and cooling to a range of temperatures as needed. | ||
==Fixed Pattern Noise== | |||
General explanation: http://en.wikipedia.org/wiki/Fixed-pattern_noise | |||
AXIOM Alpha measurements: | |||
C0 + C1 * exposuretime | |||
C0: Constant component of dark frame energy. | |||
The non-uniformity across columns is probably due to each ADC response. | |||
[[File:C0.png | 400px]] | |||
C1: Exposure dependant component of the dark energy. | |||
If all pixels are read in parallel, the non-uniformity across rows might come from temporal variation of thermal noise. | |||
But why is it exposure dependant ? | |||
[[File:C1.png | 400px]] | |||
Images generated by | |||
https://github.com/Matthias-Fauconneau/serenity/blob/master/calibrate.cc | |||
using http://files.apertus.org/AXIOM-Alpha/darkframe-*.raw16.xz | |||
Latest revision as of 07:27, 12 March 2015
Record sensor temp alongside raw, apply different noise compensation depending on temp in post.
A Peltier can help build the profiles - by heating and cooling to a range of temperatures as needed.
Fixed Pattern Noise
General explanation: http://en.wikipedia.org/wiki/Fixed-pattern_noise
AXIOM Alpha measurements:
C0 + C1 * exposuretime
C0: Constant component of dark frame energy. The non-uniformity across columns is probably due to each ADC response.
C1: Exposure dependant component of the dark energy.
If all pixels are read in parallel, the non-uniformity across rows might come from temporal variation of thermal noise.
But why is it exposure dependant ?
Images generated by https://github.com/Matthias-Fauconneau/serenity/blob/master/calibrate.cc using http://files.apertus.org/AXIOM-Alpha/darkframe-*.raw16.xz