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I always use ICNR for one simple reason. The night temperature in Melbourne can vary by as much as 15C over a night. This can also occur over just a few hours! It is impossible to get any sensible result with a library of darks.
ICNR beats the use of darks even if the temperature stays relatively constant.
To show how critical temperature is take a set of exposures with ICNR on after the camera has been on but idle for at least 10 min. Then look at the exposures just the jpgs will do. You will see your first exposure has dark holes that are deeper than the subsequent exposures. What has happened is the sensor had heated up by 2C as the first exposure was being taken due to the sensor and associated electronics consuming more power. So the ICNR 'dark' was actually taken 2C above the first light and the subtraction then caused darker holes due to the small difference in temperature.
If you do this from cold the sensor heats up by 4C! That is 2C rise from off to on and another 2C while taking long exposures.
I have now got my fridge working quite well and the next step is to control the temperature electronically. This is not easy with Peltiers but it can be done. Until this happens I will stick with ICNR.
Bert
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