mblaze Posted October 5, 2013 Share #1 Posted October 5, 2013 Advertisement (gone after registration) Is the M240's compressed DNG format truly lossless? If so, is there any reason to use the uncompressed version? Thanks Quote Link to post Share on other sites More sharing options...
Advertisement Posted October 5, 2013 Posted October 5, 2013 Hi mblaze, Take a look here M240 compressed DNG. I'm sure you'll find what you were looking for!
Stef63 Posted October 5, 2013 Share #2 Posted October 5, 2013 Yes. No. But this has been answered many times on this forum. If you want to have a look at what others have said use the search button and have fun. Quote Link to post Share on other sites More sharing options...
mblaze Posted October 5, 2013 Author Share #3 Posted October 5, 2013 Yes. No. But this has been answered many times on this forum. If you want to have a look at what others have said use the search button and have fun. Thanks for the reply. I looked, and couldn't find an authoritative answer, so I asked. Pardon me for living. Quote Link to post Share on other sites More sharing options...
MarkP Posted October 5, 2013 Share #4 Posted October 5, 2013 (edited) Pardon me for living. You're excused I don't think Stef was being abrasive with that 'have fun' sign off - easy to misinterpret brief typed posts. These are the threads you are looking for. http://www.l-camera-forum.com/leica-forum/leica-m9-forum/278070-new-m-dng-compression.html http://www.l-camera-forum.com/leica-forum/leica-m-type-240/300090-m-240-compressed-uncompressed-camera-processing.html Shoot compressed. Regards, Mark Edited October 5, 2013 by MarkP 2 Quote Link to post Share on other sites More sharing options...
k-hawinkler Posted October 5, 2013 Share #5 Posted October 5, 2013 Concise! 1 Quote Link to post Share on other sites More sharing options...
Stef63 Posted October 5, 2013 Share #6 Posted October 5, 2013 You're excused I don't think Stef was being abrasive with that 'have fun' sign off - easy to misinterpret brief typed posts. Mark Thanks Mark. I appologized via PM already for any misunderstanding. You are right, the have fun phrase was meant to be a little bit sarcastic as there seems to be some controversy around this toppic. Ten post, ten different opinions about what lossless, meaning whithout loosing anything, in the real world means. But it remains fun reading this forum. 2 Quote Link to post Share on other sites More sharing options...
mblaze Posted October 5, 2013 Author Share #7 Posted October 5, 2013 Advertisement (gone after registration) Thanks Mark. I appologized via PM already for any misunderstanding. You are right, the have fun phrase was meant to be a little bit sarcastic as there seems to be some controversy around this toppic. Ten post, ten different opinions about what lossless, meaning whithout loosing anything, in the real world means. But it remains fun reading this forum. We're all good; thanks. 2 Quote Link to post Share on other sites More sharing options...
algrove Posted October 6, 2013 Share #8 Posted October 6, 2013 Lossless is a misnomer. Some thing is lost, but what. Nothing lost with uncompressed. Quote Link to post Share on other sites More sharing options...
mblaze Posted October 6, 2013 Author Share #9 Posted October 6, 2013 Lossless is a misnomer. Some thing is lost, but what. Nothing lost with uncompressed. I'm not sure I understand what you mean. There are certainly lossless compression algorithms that can compress "typical" images to a smaller size without loss of any information. JPG is not such a scheme, but such schemes do exist. Quote Link to post Share on other sites More sharing options...
Guest roey Posted October 6, 2013 Share #10 Posted October 6, 2013 Lossless is a misnomer. Some thing is lost, but what. Nothing lost with uncompressed. In this case lossless means that you do not lose any image data. The data is simply encoded in a more efficient way. It is actually a good name. Quote Link to post Share on other sites More sharing options...
k-hawinkler Posted October 6, 2013 Share #11 Posted October 6, 2013 Could we please get beyond semantics? Here is a pretty good writeup. Lossless compression - Wikipedia, the free encyclopedia 1 Quote Link to post Share on other sites More sharing options...
01af Posted October 6, 2013 Share #12 Posted October 6, 2013 Could we please get beyond semantics? No, of course we cannot. Beyond semantics, we'd get here: jsafbvnap ibvaivbpibvi BVPAWZRGVogbsjbnü aboaeüoet ... Lossless is a misnomer. No, it isn't. Some thing is lost, but what? Redundancy. 2 Quote Link to post Share on other sites More sharing options...
lct Posted October 6, 2013 Share #13 Posted October 6, 2013 If it is like lossless audio there is indeed something lost in the process but it is more difficult to see than to hear, at least by me, so i shoot compressed as well. 1 Quote Link to post Share on other sites More sharing options...
kdriceman Posted October 6, 2013 Share #14 Posted October 6, 2013 Redundancy. Thank you, 01AF. Perhaps we can now move past this non-issue. Quote Link to post Share on other sites More sharing options...
mblaze Posted October 6, 2013 Author Share #15 Posted October 6, 2013 (edited) If it is like lossless audio there is indeed something lost in the process but it is more difficult to see than to hear, at least by me, so i shoot compressed as well. No, no information is destroyed with lossless audio either. Lossless encoding, whether for audio, images, or any other data, is a precisely defined mathematical term. It means the decoding process can recover *exactly* what was encoded. (With image data, this means the output captured by the digital sensor, not the fidelity of the capture vs the original scene. The photographic process introduces noise and distortion, but that's not what we're talking about here. We're talking only about the ability to exactly recover the output of the sensor). The naive ("uncompressed") encoding of the sensor output would be a simple list of all the rgb values, independently for each pixel. So a 10 million pixel sensor would require you to store 10 million RGB values. But you may be able to exploit redundancy found in real images to encode these 10 million values more efficiently. For example, adjacent pixels might often have exactly the same (or close) RGB values, which could be expressed more efficiently than listing identical values over and over. This won't beat the naive encoding for every theoretically possible set of pixels, but it can work quite well on actual images in practice (which are only a subset of possible images). In a lossless encoding, you can take your efficiently encoded ("compressed") data and convert it back to the *exact same* list of 10 million pixels that you would have stored if you had encoded them one by one. Not all compression schemes used in photography (or audio) are lossless. JPG and MP3, for example, are "perceptual". They work not just by exploiting redundancy, but also by "throwing out" information that you can't readily see or hear. Data encoded under a good perceptual scheme might be effectively indistinguishable -- to the human eye or ear -- from the original, but the encoding is not lossless because you can't recover the exact original data. The advantage of perceptual schemes is that they can achieve much higher compression ratios than lossless schemes, but they do so at the cost of destroying information. So my original question was about whether the M240 compressed DNG scheme is lossless in this sense. The consensus appears to be that it is. Edited October 6, 2013 by mblaze Quote Link to post Share on other sites More sharing options...
pico Posted October 6, 2013 Share #16 Posted October 6, 2013 [...] you may be able to exploit redundancy found in real images to encode these 10 million values more efficiently. For example, adjacent pixels might often have exactly the same (or close) RGB values, which could be expressed more efficiently than listing identical values over and over. [...] Mild correction - the bits must be exact to be run-length-encoded, otherwise it is lossy. So my original question was about whether the M240 compressed DNG scheme is lossless in this sense. The consensus appears to be that it is. For purposes of writing the RAW image to storage, throwing away unused contiguous empty bits per throw is lossless. If this is true, I wonder why Leica even includes a non-compressed option unless they plan to have a full 16-bit RAW one day and include it to be consistent with the (unrealized) future. Quote Link to post Share on other sites More sharing options...
mblaze Posted October 6, 2013 Author Share #17 Posted October 6, 2013 (edited) Mild correction - the bits must be exact to be run-length-encoded, otherwise it is lossy. Well, even if they're not identical, if you expect pixel RGB values are usually close to one another, you can express the difference between adjacent pixels in fewer bits than you'd need to represent each pixel separately. (Coding theory is full of tricks like this, but I'm a cryptographer, not a coding theorist.) If this is true, I wonder why Leica even includes a non-compressed option unless they plan to have a full 16-bit RAW one day and include it to be consistent with the (unrealized) future.It is odd, but I can imagine some possible reasons. There might be some image processing software that can't handle the compressed encoding (although I'm not aware of any). It's also possible that the in camera processing required for the compressed encoding introduces some tradeoff (such as power consumption or burst rate), although I'd imagine the savings from writing fewer bits to the SD card (almost certainly the bottleneck) would make up for this. Edited October 6, 2013 by mblaze 2 Quote Link to post Share on other sites More sharing options...
lct Posted October 6, 2013 Share #18 Posted October 6, 2013 No, no information is destroyed with lossless audio either. Lossless encoding, whether for audio, images, or any other data, is a precisely defined mathematical term... If i can hear a difference your mathematics are perhaps right for you but they are wrong for me i'm afraid. Quote Link to post Share on other sites More sharing options...
mblaze Posted October 6, 2013 Author Share #19 Posted October 6, 2013 If i can hear a difference your mathematics are perhaps right for you but they are wrong for me i'm afraid. Maybe you think you can hear a difference, but all lossless encoding schemes (whether compressed or not) will decode to exactly the same result, by definition. Mathematical concepts have the annoying property that they don't care whether you like them or not. 2 Quote Link to post Share on other sites More sharing options...
lct Posted October 6, 2013 Share #20 Posted October 6, 2013 I sense more differences between AIFF and MOV files than between TIF and 100% JPEG. Theory and practice as usual. Quote Link to post Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.