Hmmm I've always been told that RAW files are lossless...
Seems like I'm wrong. Stumbled across this about compressed NEFs
brief summary - loss of data in the shadow region due to lower resolution in quantizing data. Compresed NEFs are only capturing 9.4 bits of data as opposed to 12 bits of data.
Means: Loss of shadow detail.
The maths and the mechanical and technical details all works out, though I've not gotten my hands on any coding to verify, but this guy seems solid enough.
subsequently did a few searches.. and this:
OK I know this may not be news to some of you, but hey it's definitely news to me. I've always been brainwashed to accept that RAW files are not lossy. I know most of you will say that you never had problems with compressed NEFs, but I think should stop with the "all RAW files are lossless" thing.As with previous Nikon digital SLR models, Nikon describes the compressed RAW setting as numerically lossy but visually lossless. Translated, that means the RAW data after compression is not numerically identical to the RAW data before compression: some picture information has changed. Like a low-compression, high-quality JPEG setting, however, Nikon is promising that it will not be possible to see the data loss.