5 Replies Latest reply on Dec 20, 2009 2:44 PM by Panoholic

    M-RAW and S-RAW of Canon 7D with 5.6

    herbie0815

      Hello,

       

      as I see, unfortunately version 5.6 doesn't really support M-RAW and S-RAW of Canon 7D. DNG files for M-RAW will inflate about 50% in size of the original M-RAW file (18MB -> 28MB). The only intention to shoot in M-RAW is the smaller size of files.

       

      Best regards

      Herbie

        • 1. Re: M-RAW and S-RAW of Canon 7D with 5.6
          Panoholic Level 2

          1. The size reduction by DNG vs. CR2 files is not really big, that's not a solid reason to go DNG.

           

          2. The mRaw and sRaw files are not raw any more; they are demosaiced in such a format, which can not be stored identically in DNG. The conversion to DNG has to "expand" the original data, thus the result will be much larger than the CR2, even if compressed.

           

          Gabor

          • 2. Re: M-RAW and S-RAW of Canon 7D with 5.6
            herbie0815 Level 1

            > 1. The size reduction by DNG vs. CR2 files is not really big, that's not a solid

            > reason to go DNG.

             

            yes, that's true. I don't use DNGs because of the size. But sometimes I shoot M-RAW because of the size. And I expect that the resulting DNG is smaller than the DNG converted by a normal RAW. But it's larger... :-/ Honestly I expect a DNG which is smaller than the CR2 (18MB), but as I said, not larger than a normal RAW. The normal RAW has got 18MP and the M-RAW has got 10MP, and the DNG of M-RAW is larger than the 18MP CR2...

             

            > 2. The mRaw and sRaw files are not raw any more; they are demosaiced in such

            > a format, which can not be stored identically in DNG. The conversion to DNG has

            > to "expand" the original data, thus the result will be much larger than the CR2,

            > even if compressed.

             

            Hmm, I'm not satisfied about this explanation. Maybe I don't understand the technical side, but as I said, the M-RAW has got 10MP and the normal RAW has got 18MP. I really expect that the DNG from M-RAW is smaller than the one from normal RAW...

             

            Best regards

            Herbie

            • 3. Re: M-RAW and S-RAW of Canon 7D with 5.6
              Panoholic Level 2
              function(){return A.apply(null,[this].concat($A(arguments)))}

              herbie0815 wrote:


              > 2. The mRaw and sRaw files are not raw any more; they are demosaiced in such

              > a format, which can not be stored identically in DNG. The conversion to DNG has

              > to "expand" the original data, thus the result will be much larger than the CR2,

              > even if compressed.

               

              Hmm, I'm not satisfied about this explanation. Maybe I don't understand the technical side, but as I said, the M-RAW has got 10MP and the normal RAW has got 18MP. I really expect that the DNG from M-RAW is smaller than the one from normal RAW...

               


              Well, if you don't understand the technical side, then you don't have any basis to expect a certain behavior, which reflects purely technical aspects. Anyway, I try to give a brief explanation of it.

               

              The Bayer type raw data has only one value per pixel, that is the "red", "green" or "blue" raw value (which is not identical to the red, green or blue value from RGB). The mRaw and sRaw are demosaiced, each pixel has three components, red, green and blue. The red and blue components are the same for two neighbouring pixels, therefor they are not stored twice. (Think of this: the sRaw has only one quarter as many pixels as the normal raw, but the file size is closer to the half of the size of the normal raw). However, DNG does not support storing the data this way, therefor the DNG converter has to create a file, in which all pixels have all three components; thus the DNG contains much more data than the respective sRaw or mRaw.

               

              Gabor

              • 4. Re: M-RAW and S-RAW of Canon 7D with 5.6
                herbie0815 Level 1

                Hi,

                 

                > Well, if you don't understand the technical side, then you don't have any basis to

                > expect a certain behavior, which reflects purely technical aspects

                 

                oh no, I don't agree! I'm a software engineer for myself, so you can't tell me that there is no other way than inflating the data as it is done

                 

                > The Bayer type raw data has only one value per pixel...

                 

                I know...

                 

                > However, DNG does not support storing the data this way

                 

                Ok, it doesn't support it. That is the same statement which I said already 2 postings before.

                 

                In my opinion, you have to admit, that it's not so easy to explain that a small file will result in such a big file. Your explanation was not very satisfactory. But you told me that the DNG converter doesn't support converting a M-RAW to an acceptable size. That's the point. But it isn't the same than saying that it is impossible...

                 

                Best regards

                Herbie

                • 5. Re: M-RAW and S-RAW of Canon 7D with 5.6
                  Panoholic Level 2
                  function(){return A.apply(null,[this].concat($A(arguments)))}

                  herbie0815 wrote:


                  In my opinion, you have to admit, that it's not so easy to explain that a small file will result in such a big file. Your explanation was not very satisfactory. But you told me that the DNG converter doesn't support converting a M-RAW to an acceptable size. That's the point. But it isn't the same than saying that it is impossible...

                   


                  1. It is easy to explain it to someone, who is familiar with the lossless JPEG encoding, but such are rather the exception among photographers.

                   

                  2. It is impossible with the given DNG specification, for that does not allow for subsampling.

                   

                  Gabor