uhoh7 Posted January 24, 2017 Share #81 Posted January 24, 2017 (edited) Advertisement (gone after registration) You are clearly unfamiliar with the science of data compression. You might enjoying reading the reading literature more than you enjoy ranting about something you choose to believe is something like Alternative Fact. And how do you think reading HEX even matters here? Leica has published a document called "Technical Data". The information in that publication is binding. The technical data says that the M (Typ 240) stores the image either as JPEG file or as DNG ; if DNG, you can store the image in uncompressed or in losslessly compressed format. There is a number of compression algorithms known which will produce losslessly compressed images. Leica does not say which format they chose. It does not matter which format they chose. The document mentioned above is legally binding. If you want to know which algorithms are used in compressing the file you can find out as I wrote above. Testing an image compression software in order to see whether there will be any losses is pointless. If you know how the algorithm works, you don't need a test as it can be easily shown whether the algorithm is lossy or not. If you do not know how the algorithm works, testing is pointless as you don't know what you should be looking for and which situation may demonstrate the losses. So: when Leica state that they apply lossless compression to the image, they mean that they used an algorithm that's proven to be lossless. If pressed, I would guess that they might have chosen the LZW algorithm, which is used in some ZIP files as well. But then, they might have chosen another one on account of the copyright issues in connection with LZW. Look at the file. Just more ways to say you don't know, Thanks Thanks what I thought. You just read the claim and parrot. It may well be truly lossless or effectively lossless, but you two have no idea. "it's in the technical data!" OMG seriously? You ever weigh cameras? You ever check the stated measurements M240 vs M9? :rolleyes Edited January 24, 2017 by uhoh7 Quote Link to post Share on other sites More sharing options...
Advertisement Posted January 24, 2017 Posted January 24, 2017 Hi uhoh7, Take a look here DNG compressed VS uncompressed?. I'm sure you'll find what you were looking for!
Exodies Posted January 24, 2017 Share #82 Posted January 24, 2017 You seem to think lossless is a boast and so tricky to achieve that it is worth taking a risk on letting the marketing department claim it falsely. Well it's not. 3 Quote Link to post Share on other sites More sharing options...
pico Posted January 24, 2017 Share #83 Posted January 24, 2017 (edited) You seem to think lossless is a boast and so tricky to achieve that it is worth taking a risk on letting the marketing department claim it falsely. Well it's not. Yes! Compression algorithms are open source, and so widely shared that they are the easy part of implementation. Anyone implementing such uses proven code; they proof it before release. And as Pop wrote, there are contracts to enforce compliance and deviating from the contract has dire consequences. Compressed in this case is simple, the least of our concerns. . Edited January 24, 2017 by pico 2 Quote Link to post Share on other sites More sharing options...
ECohen Posted January 24, 2017 Author Share #84 Posted January 24, 2017 (edited) Just more ways to say you don't know, Thanks Thanks what I thought. You just read the claim and parrot. It may well be truly lossless or effectively lossless, but you two have no idea. "it's in the technical data!" OMG seriously? You ever weigh cameras? You ever check the stated measurements M240 vs M9? :rolleyes "You ever weigh cameras?" Seriously ....you weighed your camera? I may pick the bag packed up and decide if I'm going to carry it all day.......its not like your packing the Space Shuttle. Why would you weigh your camera?....to prove the Leica specs wrong....by a few grams ....Then what? Edited January 24, 2017 by ECohen 1 Quote Link to post Share on other sites More sharing options...
marchyman Posted January 25, 2017 Share #85 Posted January 25, 2017 Why don't you just share your knowledge and tell us the compression method for Leica DNG, how you determined it, and how it's verifiable. Maybe you have not done it? Jpeg2000? Quote Link to post Share on other sites More sharing options...
marchyman Posted January 25, 2017 Share #86 Posted January 25, 2017 (edited) Why don't you just share your knowledge and tell us the compression method for Leica DNG, how you determined it, and how it's verifiable. Maybe you have not done it? Jpeg2000? Hmmm, that got posted but not my response. I'll edit this post, but it will take a while. Short answer is not JPEG 2000. The DNG spec from Adobe -- it is Adobe's specification, not Leica's -- initially allowed for three compression options for compressing raw image data. The DNG spec is based upon the TIFF spec and uses some of the TIFF tags to describe the data. TIFF has a compression tag. The DNG spec calls out these values: Value = 1: Uncompressed data. (option 1) Value = 7: JPEG compressed data, either baseline DCT JPEG, or lossless JPEG compression. (options 2 and 3) Note the "either". The spec continues with this: If PhotometricInterpretation = 6 (YCbCr) and BitsPerSample = 8/8/8, or if PhotometricInterpretation = 1 (BlackIsZero) and BitsPerSample = 8, then the JPEG variant must be baseline DCT JPEG. (Lossy compression -- option 2) Otherwise, the JPEG variant must be lossless Huffman JPEG. (option 3). If you run the third party tool "exiftool" on a DNG from a Leica Q you'll see it reports "Compression: Uncompressed". It is reading the TIFF compression tag and seeing a value of 1. The file size is about 44 MB. Bringing that image into ACR via photoshop and saving it as a DNG results in a (lossless) compressed version that is about 26 MB in size. "exiftool" run on that file reports "Compression: JPEG". It also reports: Photometric Interpretation : Color Filter Array Bits Per Sample : 16 Either one of those rules out using lossy compression (unless specifically asked for as of DNG version 1.4). When I asked ACR to create a lossy version of the same DNG the resulting file size was about 7 MB. "exiftool" says this about the resulting file: Compression: Lossy JPEG Exiftool knows the difference. When I ask exiftool to look at one of the DNGs created by my M 262 it reports "Compression: JPEG". That is the how it reports lossless compression. If you want to know more about the specific compression used see How DNG compresses raw data with lossless JPEG92 - ThNdl Edited January 25, 2017 by marchyman 5 Quote Link to post Share on other sites More sharing options...
uhoh7 Posted January 27, 2017 Share #87 Posted January 27, 2017 (edited) Advertisement (gone after registration) Hmmm, that got posted but not my response. I'll edit this post, but it will take a while. Short answer is not JPEG 2000. The DNG spec from Adobe -- it is Adobe's specification, not Leica's -- initially allowed for three compression options for compressing raw image data. The DNG spec is based upon the TIFF spec and uses some of the TIFF tags to describe the data. TIFF has a compression tag. The DNG spec calls out these values: Value = 1: Uncompressed data. (option 1) Value = 7: JPEG compressed data, either baseline DCT JPEG, or lossless JPEG compression. (options 2 and 3) Note the "either". The spec continues with this: If PhotometricInterpretation = 6 (YCbCr) and BitsPerSample = 8/8/8, or if PhotometricInterpretation = 1 (BlackIsZero) and BitsPerSample = 8, then the JPEG variant must be baseline DCT JPEG. (Lossy compression -- option 2) Otherwise, the JPEG variant must be lossless Huffman JPEG. (option 3). If you run the third party tool "exiftool" on a DNG from a Leica Q you'll see it reports "Compression: Uncompressed". It is reading the TIFF compression tag and seeing a value of 1. The file size is about 44 MB. Bringing that image into ACR via photoshop and saving it as a DNG results in a (lossless) compressed version that is about 26 MB in size. "exiftool" run on that file reports "Compression: JPEG". It also reports: Photometric Interpretation : Color Filter Array Bits Per Sample : 16 Either one of those rules out using lossy compression (unless specifically asked for as of DNG version 1.4). When I asked ACR to create a lossy version of the same DNG the resulting file size was about 7 MB. "exiftool" says this about the resulting file: Compression: Lossy JPEG Exiftool knows the difference. When I ask exiftool to look at one of the DNGs created by my M 262 it reports "Compression: JPEG". That is the how it reports lossless compression. If you want to know more about the specific compression used see How DNG compresses raw data with lossless JPEG92 - ThNdl TY for such a nice informative post. I'm sorry to be such a twit in previous posts, but really there has been nothing till this past "Leica Says So---you Idiot" and "Lossless mean Lossless---you Idiot" LOL Not from you. Even in middle school science the grade for making a claim with no specific data to back it starts with F--no credit for legal liability You give us data!!!!! I'm not sure the info you have gleened truly verifies the claim (it certainly may), but you take some great clear steps which help myself and others learn more and understand the nitty gritty better Now I something to really go on and get some further understanding Thank You !!!! Edited January 27, 2017 by uhoh7 Quote Link to post Share on other sites More sharing options...
Exodies Posted January 27, 2017 Share #88 Posted January 27, 2017 Good grief. Quote Link to post Share on other sites More sharing options...
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