Archived posting to the Leica Users Group, 2015/07/14
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]It varies in size depending on the scene (unlike a Sony which is always the same size so shows lossy compression), my S2 shots are usually smaller files than the Monochrom (which cannot be compressed). john -----Original Message----- Yew, I know. I was just surprised at first that it could be a factor of two. Then I stopped being surprised after I thought about it for a few minutes. Herbert Kanner kanner at acm.org 650-326-8204 Question authority and the authorities will question you. > On Jul 14, 2015, at 7:28 PM, Richard Man <richard at richardmanphoto.com> wrote: > > Lossless compression is not new or difficult, even Huffman did it in > 1952 as a term paper project :-) > > On Tue, Jul 14, 2015 at 6:55 PM, Herbert Kanner <kanner at acm.org> wrote: > >> I was surprised to see in the manual that there was lossless >> compression of the DNG. So I thought I'd try it out by taking two >> shots, one compressed and one uncompressed. When I looked at my DNG >> file, I was astounded to find a DNG of over 40 MB and a compressed >> one of about half that size. (I deleted the negatives before thinking >> of writing this, so I can't give you exact numbers. >> >> Well, I was at first astounded that lossless compression could be >> that effective. Then I thought about the details of an image. Except >> where there is really fine structure in the image, there will be >> areas where the data does not change. A simple number triple, one >> giving a value for, say the red pixel, the second giving a starting >> location in the file, and the the third the number of consecutively >> stored pixels having the same value, could easily result in a factor of two compression for lots of pictures. >> And what I just described is a very unsophisticated compression >> method. If anyone knows more about how this might have been done, I'd >> be very interested. >> >> kanner at acm.org >> 650-326-8204 >> >> Question authority and the authorities will question you. >>