Re: Dotphoton Raw / 'Rawsie' - any opinions on this raw compression witchcraft?
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Hi The_Suede, I am one of the devs of 'Rawsie', sorry for the late reply, I was just made aware of your post. Indeed, we use the lossless JPEG coder already present in the DNG SDK. Coding is done over the native bit-depth of the camera (DNG supports up to 16 bits). The way that we achieve better results is that we calibrate each individual camera, at each iso and most shutter speed, in the lab. From that we generate custom coding per camera and per iso. The quality is not bit-for-bit lossless, but the error generated with respect to the noise is approximately 1/10th of that of lossy JPEG at the same file size.
You are completely right about black point: one must be particularly careful around it because, as you mention, even if the signal is smaller than the noise, it can be recovered by denoisers, or even visually by the human eye. We found that it's best to keep values around the black point untouched, as anyway they don't eat up much space.
As far as I see, values below the black point are preserved in the DNG, and it's then up to the development software to decide what to do about them, I agree with you that it's best not to clip them.
About RED and patent issues, my understanding is that DNG pre-dates the RED patents. My superficial understanding is that the RED patent is quite broad, but that even though some of their claims may not hold, Sony and Apple implemented systems that were remarkably similar to RED's i.e. Split the R,G,B image planes, apply amplitude scaling per-channel, apply wavelet compression, de-compress and scale back, with the purpose of having compression errors become invisible to the human eye.
Personally, I hope that DNG will remain supported for a long time. Most raw files, including DNG, are basically TIFF. The DNG SDK is open source, and, although it seems to lack some documentation in the code, once you understand it, it is rather nice to use. Somehow, all my favourite cameras use it: Ricoh, Sigma, Leica. Also, of course, I do love to be able to easily open the files and try to write my own image development software :-), after working with DaVinci Resolve for video, no photo editing software makes sense to me anymore ...