LibRaw PixelShift2DNG: How it Converts Sony ARQ Files to DNG
Related: digital sensor, LibRaw, pixel shift, PixelShift2DNG, Sony, Sony Pixel Shift, true-color sensor or image
re: Adobe DNG Converter
re: Sony pixel shift
I asked Alex Tutubalin of LibRaw how PixelShift2DNG converts Sony ARQ files to DNG:
ARQ files contains four pixel values per pixel in ARQ file: R, G, B, and G 2.
PixelShift2DNG averages two greens and saves as DNG.
DIGLLOYD: for full clarity: the two green channels of the Bayer matrix sensor are stored separately in the ARQ file, which has no practical value that I am aware of; it just takes up more space. Plus the ARQ file does no compression and so the files are needlessly oversized.
PixelShift2DNG averages these two channels (thus reducing green channel noise), and then saves a lossless compressed DNG for about a 64% reduction in file size.
I am aware of no reason that I would ever want to go back into Sony Edit to use the ARQ file, so storing a file that is 1/3 the size is a huge win. If the file is solid (no artifacts), then I suppose I can throw away of the original pixel shift captures as well, or perhaps (more cautiously), all but the first frame for each pixel shift capture.
Adobe DNG Converter produces an even smaller file (12-13MB smaller), though I’m not sure why—I’ve inquired.
