This is an issue of intense interest to the astronomy community, and might crop up in micro/macro work with multi-second exposures. I paid attention because I often use longer exposures as a way of working around shutter vibration at high magnifications.
The primary reference is to a Yahoo/PanoToolsNG posting here. It links to a mixed English/French article at astrosurf.com, here.
From the linked article:
--RikConclusion
...
The behaviour of Nikon DSLR are radically different from the Canon ones for long exposure:
- For Nikon, the hot pixels are eliminated by a sophisticated digital processing external to the sensor. During this digital processing, the signal of the neighboring pixels is also affected. The damage of such processing is well-known in astronomy: the weak stars are also eliminated and the image loose photometric qualities on stellar like objects.
- For Canon, the thermal signal is reduced for each pixel by a differential reading method. The thermal signal level measured at the output of the sensor is very low. The residual can efficiently be removed during the image processing (a simple substraction of a reference dark signal map).
It is tragic to see that Nikon solved the problem of thermal signal by a digital processing of the RAW files (i.e. NEF files do not contain true raw data). This processing can surely meet the daytime users and the high performance for main application is evident. But by repeating the same mistake made on the D70 and the D200 (equipped with a CCD) on the news Digital SLR Nikon probably divorces once more with the astronomical community.
Today the Canon and Pentax cameras seem to be the only ones useable digital SLR for efficient and advanced astronomy.
