dpattinson Posted May 18, 2007 Share #1 Posted May 18, 2007 Advertisement (gone after registration) So I noticed people suggesting that compression of the DNG raw files 'must lose quality', even though Leica state they are using lossless compression. I don't know what compression algorithm Leica are using, however I can state categorically that it is eminently possible to compress digital data without loss. Anyone who has unzipped a .zip file has in fact made use of lossless compression. The tradeoff in deciding whether or not to use lossless compression must either be around the relative speed of compression vs the time it takes to write to storage media , or about how many shots you can store per GB of storage. If you are currently limited by the write speed to storage, then compressing first means less data to write and a faster write - if write speed is not a limiting factor then compression would waste time. I don't know which reason has prompted Leica to use compressed DNG's, however either way - you're not losing data if it really is lossless Link to post Share on other sites More sharing options...
Advertisement Posted May 18, 2007 Posted May 18, 2007 Hi dpattinson, Take a look here Lossless compression of DNG files. I'm sure you'll find what you were looking for!
stunsworth Posted May 18, 2007 Share #2 Posted May 18, 2007 David sorry, you're wrong. While it's perfectly possible to compress data in a lossless fashion, with the M8 Leica use a kind of look up table to compress the data coming off the sensor to 8 bits. This involves throwing away some highlight data. Whether or not this is a good or bad thing has been done to death on some of the largest threads ever seen here :-) Link to post Share on other sites More sharing options...
ho_co Posted May 19, 2007 Share #3 Posted May 19, 2007 In addition, a complete description of the process, its advantages and limitations appeared in LFI several issues back. The article was written by forum member Michael J Hußmann. --HC Link to post Share on other sites More sharing options...
dpattinson Posted May 21, 2007 Author Share #4 Posted May 21, 2007 Thanks for clearing that up - not lossless compression after all then Link to post Share on other sites More sharing options...
albertknappmd Posted May 21, 2007 Share #5 Posted May 21, 2007 and not at loss regarding this thread... :D In practical terms, the actual loss of highlight data is more theoretical than practical. The human eye cannot notice the difference and furthermore, playing around with the histogram of my M8 files and doing rather deliberate but aggressive maneuvers in 16 bits has not resulted in posterization at all.... Link to post Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.