pmun Posted June 12, 2009 Share #1 Posted June 12, 2009 Advertisement (gone after registration) Why are my GRD2 DNG files approx 14MB while my M8 DNG files are only 10MB please? Link to post Share on other sites More sharing options...
Advertisement Posted June 12, 2009 Posted June 12, 2009 Hi pmun, Take a look here M8 DNG file size. I'm sure you'll find what you were looking for!
Shootist Posted June 12, 2009 Share #2 Posted June 12, 2009 16bit to 8bit??? Just a guess. Why are you worried about it? Don't you like the M8 files? Bigger is not always better. I use enough HD space already, especially if you process the DNG's into TIFF or PSD files. They get to around 59MB without any layers. Add in LR compatiblility if you use any layers and the file jumps to 160+MB. Link to post Share on other sites More sharing options...
pmun Posted June 12, 2009 Author Share #3 Posted June 12, 2009 Thanks Shootist, I’m not worried, just curious. I assumed a larger sensor would create larger files. I’m new to the M8, but I’m happy with the files so far, much more detail than my GRD2, that’s another reason why I thought the files would be bigger. Link to post Share on other sites More sharing options...
jaapv Posted June 12, 2009 Share #4 Posted June 12, 2009 Because Leica has a very intelligent compression that works with pointers to LUT with logarithmic compression. Link to post Share on other sites More sharing options...
pmun Posted June 13, 2009 Author Share #5 Posted June 13, 2009 Because Leica has a very intelligent compression that works with pointers to LUT with logarithmic compression. What does 'pointers to LUT with logarithmic compression' mean please? Link to post Share on other sites More sharing options...
scott kirkpatrick Posted June 13, 2009 Share #6 Posted June 13, 2009 What does 'pointers to LUT with logarithmic compression' mean please? It has been a long night, and Jaapv wasn't very clear. Each pixel value in the DNG file from an M8 is actually the square root of the raw data, stored as an 8-bit number, so 10 MPixels gives you 10 MBytes. That reduces the wasted bits in the highights and has little effect on the shadow information. There was a long debate on this, but there seems to be no or little image degradation in return for a 2x gain in processing speed and storage. There are no logarithms involved. The mapping from the original data to the saved data is contained in a look-up table (LUT) which is pasted into every DNG file. This is a standard trick that any DNG format file can use. There is an article by Michael Hussman, I think, in LFI about a year ago that explains the transformation and shows some pictures made before Leica decided to use this compression, to show why they concluded it didn't hurt to do so. scott Link to post Share on other sites More sharing options...
carstenw Posted June 13, 2009 Share #7 Posted June 13, 2009 Advertisement (gone after registration) In other words, the Leica M8 DNGs are almost exactly the same size for each shot, namely the size of an 8-bit single-channel image (R or G or B for each pixel). 10MB = 10MP @ 1 byte per pixel. The quality is much better than for normal 8-bit images, however, since the values are more evenly distributed throughout the brightness range, and not almost all in the bright areas. Link to post Share on other sites More sharing options...
pmun Posted June 13, 2009 Author Share #8 Posted June 13, 2009 Thanks very much for explaining. Link to post Share on other sites More sharing options...
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