gravastar Posted October 18, 2006 Share #41 Posted October 18, 2006 Advertisement (gone after registration) If I open an M8 DNG file in C1 Pro 3.7.5 and stretch the shadows or highlights to extreme limits I don't see any "banding". All that appears is noise in the shadows. If after RAW convertion to a 16 bit TIFF I do a further stretch of highlights or shadows in CS2 any banding that is visible is in what would have been the mid to dark tones. We're going to have to be patient and wait for samples from production firmware to become available before forming any useful conclusions. Bob. Link to post Share on other sites More sharing options...
Advertisement Posted October 18, 2006 Posted October 18, 2006 Hi gravastar, Take a look here M8-why 10MB-vs-DMR 20MB. I'm sure you'll find what you were looking for!
marknorton Posted October 18, 2006 Share #42 Posted October 18, 2006 I agree, and for that reason, I'm not going back to Leica for more information. They will legitimately say that any and all DNGs out there shouldn't be and you should wait until production level firmware. That's fine, but they are really taking this to the wire or else they are even now thinking about the best way to say "6 months delay". Link to post Share on other sites More sharing options...
Guest guy_mancuso Posted October 18, 2006 Share #43 Posted October 18, 2006 I've done a bit of research about this. If you look at the Adobe DNG spec, downloadable from: http://www.adobe.com/products/dng/pdfs/dng_spec.pdf You'll notice DNG uses "lossless Huffman JPEG compression" to achieve the filesize saving. (p.15, "3. Restrictions and Extensions to Existing TIFF Tags" / "Compression") Although it sounds bad to use JPEG compression - doesn't it imply "lossy"? - if you look up "lossless Huffman" you'll see the compression is indeed truly loss-less and done without discarding any bits. See: 1. The Huffman compression algorithm 2. Image Compression: JPEG Huffman... So... don't worry about it. Huffman compression is merely an efficient way to save disc-space by mapping redundant bits to achieve approx 2:1 compression. Nothing is discarded and the image is not remapped or downgraded to 8-bit! It appears Leica were ultra-conservative with the DMR and switched off the DNG-compression option. With the M8, they got with the program and switched it back on. They pay a small cost in increased processing time, but with faster chips this is a moot point, and ultimately they save time by writing 50% less data to storage. :?) This makes the most logical sense so far, I just don't think 8 bit is involved anywhere . It is 16 bit and now they are using a different way to compress than the DMR which really is not compressed at all or very little. We will have to see how this all comes down. But leica going to 8 bit would be Chapter 11 Link to post Share on other sites More sharing options...
clayh Posted October 18, 2006 Share #44 Posted October 18, 2006 Well, it is mathematically clear that Leica have to be doing some sort of compression to get the file down to that size. If you do the math with the sensor resolution, you end up at 10.314M pixels. At one byte (=8bits) per pixel, that pretty much equals their stated file size if there is NO compression. The only way to get a 16 bit number stored for each sample is to compress the file. I think it is most likely that they are doing some sort of loss-less compression like the Huffman algorithm someone already mentioned. This makes the most logical sense so far, I just don't think 8 bit is involved anywhere . It is 16 bit and now they are using a different way to compress than the DMR which really is not compressed at all or very little. We will have to see how this all comes down. But leica going to 8 bit would be Chapter 11 Link to post Share on other sites More sharing options...
nemeng Posted October 18, 2006 Share #45 Posted October 18, 2006 Thanks for the clarification JL and JC. I really don't understand what the problem is here. The M8 RAW files are 16-bit. They have always been 16-bit. They are written to disc using "Lossless Huffman JPEG Compression", thus requiring only 10 MB space vs the DMR's 20 MB. As I have shown earlier, no data is lost or destroyed or transposed. 16-bits in. 16-bits out. Loss-less. The 8-bit business is a Furphy. It appears to have arisen because someone didn't understand (and was too lazy to look up) how the DNG compression scheme works :?) Link to post Share on other sites More sharing options...
sdai Posted October 18, 2006 Share #46 Posted October 18, 2006 I repeat, the question is not about compression ... now I actually have wasted some time read the DNG specification Andrew has linked in his previous thread ... on pages 15 through 16, it explains a lot about the file tags. Now let's go back to the file tag Barry Pearson has extracted from one M8 DNG file: NewSubFileType: Main Image ImageWidth: 3920 ImageLength: 2638 BitsPerSample: 8 Compression: Uncompressed PhotometricInterpretation: CFA It clearly shows the DNG file is NOT compressed, with a PhotometricInterpretation value set to CFA, which is part of the TIFF-EP specification. Why do you guys keep talking about JPEG Huffman Lossless compression? it has nothing to do with that ... do not confuse yourselves. Link to post Share on other sites More sharing options...
Guest guy_mancuso Posted October 18, 2006 Share #47 Posted October 18, 2006 Advertisement (gone after registration) Now going back to what I said before with Andrews explanantion. On the DMR with firmware 1.3 they can turn the compression on and gain buffer speed and read and write times plus save battery life and all at the flip of a switch instead of a physical processor upgrade. Well the do it and is it possiabe i don't know but it sounds like it would be worth it Link to post Share on other sites More sharing options...
sdai Posted October 18, 2006 Share #48 Posted October 18, 2006 Guy ... this has nothing to do with compression. Link to post Share on other sites More sharing options...
Guest guy_mancuso Posted October 18, 2006 Share #49 Posted October 18, 2006 Simon Canon and Nikon compress there raw files . The DMR is not why would leica take notadvantage of that if they can. Simon honestly you know as well as i if leica went 8 bit it would be the death of them, I frankly can't imagine they would even think about doing it . Link to post Share on other sites More sharing options...
sdai Posted October 18, 2006 Share #50 Posted October 18, 2006 Simon Canon and Nikon compress there raw files . True ... but they never play with the color depth in RAW files. if leica went 8 bit it would be the death of them, I frankly can't imagine they would even think about doing it . I'm going to call my priest right now ... man, I do wish this is just one of the many rumors the dpreviewers spreaded on the web - there must be someone out there who could tell me what was wrong! Link to post Share on other sites More sharing options...
nemeng Posted October 18, 2006 Share #51 Posted October 18, 2006 I repeat, the question is not about compression ... Actually, it is :?) The whole point of this thread is "M8-why 10MB-vs-DMR 20MB"! Which I believe we have answered fully and correctly. As for the EXIF tag indicating only 8-bits... most likely this is a bug. The actual image is 16-bit. I think it's merely a case of accidentally writing "8-bit" in a tag when they should have written "16-bit". I ran "exiftool" over the M8 DNG sample I have (the infamous "Photokina Woman" shot) and indeed the EXIF tag indicated a sample size of only 8-bits. Yet the RAW converted image is 59.2 MB and opens as a fully fledged 16-bit TIFF in Photoshop. So clearly what is noted in the tag is wrong. So methinks someone is trying to read far too much into a simple typo in a pre-release version of the EXIF tag-writing code! Photoshop doesn't look at the EXIF data when opening RAW converted files anyway. It is only used as a form of humanly readable text-data for cataloging etc. :?) Link to post Share on other sites More sharing options...
sean_reid Posted October 18, 2006 Share #52 Posted October 18, 2006 Sean, Considering that's what Leica has stated in all of its literature, I'm sure you're correct. However, I'm going to hang on to those 20MB files -- who knows, maybe they'll become valuable Leica "collectibles." ;-) Larry Could be. That must have been a camera with very early firmware or something like that. Cheers, Sean Link to post Share on other sites More sharing options...
sean_reid Posted October 18, 2006 Share #53 Posted October 18, 2006 Folks, you are worrying about nothing. Cheers, Sean Link to post Share on other sites More sharing options...
clayh Posted October 18, 2006 Share #54 Posted October 18, 2006 I'm not worried. I work with geophysical seismic data every day, and the industry has been doing lossless compression of seismic data for almost two decades now. And that data has a whole heck of lot more dynamic range than you would ever see in a raw image file. Folks, you are worrying about nothing. Cheers, Sean Link to post Share on other sites More sharing options...
sdai Posted October 19, 2006 Share #55 Posted October 19, 2006 AThe actual image is 16-bit. How do you know? I ran "exiftool" over the M8 DNG sample I have (the infamous "Photokina Woman" shot) and indeed the EXIF tag indicated a sample size of only 8-bits. Yet the RAW converted image is 59.2 MB and opens as a fully fledged 16-bit TIFF in Photoshop. It doesn't matter how many bits/channel a RAW file retains, Photoshop could always render a 16-bit TIFF as the end result ... Canon's CR2 files are 12-bit/channel, Nikon's NEFs are 12bit/channel, Fuji's RAFs are 14-bit/channel ... yet they all come out as 16 bit TIFF from many programs. Link to post Share on other sites More sharing options...
sdai Posted October 19, 2006 Share #56 Posted October 19, 2006 Folks, you are worrying about nothing. I was kind of expecting you jumping in the thread should that signals good, Sean ... Worrying about a camera is the last thing I would add on to my agenda ... and I've never kept any digital one for more than 6 months. What's different is only the speed I dumped them on the auction sites. Cheers, Link to post Share on other sites More sharing options...
clayh Posted October 19, 2006 Share #57 Posted October 19, 2006 I'm guessing what Simon is saying is that there is a difference between file compression and the dynamic range of the sensor itself. What the camera does to compress the data is a completely separate issue from the dynamic response/capabilities of the sensor. It is sort of silly quibbling over this, because discerning the sensor's dynamic range from the way the data ends up being stored is heavy on pull-it-out-of-your-butt guesswork at best. Link to post Share on other sites More sharing options...
sdai Posted October 19, 2006 Share #58 Posted October 19, 2006 For those who don't know what a color depth is about ... here's something fun and good to read, and yes, Clay, it has nothing to do with compression. Tonal quality and dynamic range in digital cameras Link to post Share on other sites More sharing options...
ho_co Posted October 19, 2006 Share #59 Posted October 19, 2006 I'm not worried. I work with geophysical seismic data every day, and the industry has been doing lossless compression of seismic data for almost two decades now. Clay--May I say; ahem; "that's earthshaking!"? (Someone had to say it, right?) All-- Seriously: Sean has twice said we're barking up the wrong gefilte fish. Several people have said Leica would never recover if they gave us 8-bit data. Andrew has deciphered the data and found them not 8-, not 12-, but 16-bit. Leica is the only company with 16-bit raw on the market. Leica has asked us not to disseminate (ergo not to discuss) the M8's DNGs. I'm learning a lot about color and raw and how brilliant the rest of you guys are--but I think this thread may be a very interesting but useless dead end. Has anybody noticed that Leica takes good pictures? Has anybody else heard that Leica has been very surprised and pleased at the quantity of orders for M8's? Does anyone think Leica will jeopardize that? --HC Link to post Share on other sites More sharing options...
nemeng Posted October 19, 2006 Share #60 Posted October 19, 2006 How do you know? Sigh. Troll alert! Google "imagemagick identify" and "dcraw" for handy image-processing command line tools. Link to post Share on other sites More sharing options...
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