7 Replies Latest reply on Jan 2, 2013 10:51 AM by Mr_Pedantic

    Modified JPEG

    Mr_Pedantic Newcomer

      I just ran some file synchronisation software and it reported that a JPEG file had been changed on my C drive. I didn't remember changing it so checked. I have a trial version of Photoshop CS6. It seems that if a JPEG is opened into Camera RAW and then opened into Photoshop, then Windows reports it as modified, even if no changes were made.

       

      My question is does this behaviour result in the image being resaved with a loss of quality each time that it is opened this way?

        • 1. Re: Modified JPEG
          Rockstar

          Every single time any JPEG is saved (not just "opened") there's a loss of quality due to re-compression, no exceptions.  It doesn't matter whether you have modified it or not, nor does it matter whether the OS reports it as modified or not.

           

          Again, the compression occurs every time you save or resave a JPEG, any JPEG. Compression inexorably means image deterioration.

           

          The best solution is never to work on a JPEG, ever.  Use the format only as a final, target format when absolutely necessary but avoid it otherwise.

          • 2. Re: Modified JPEG
            c.pfaffenbichler Legend

            It seems that if a JPEG is opened into Camera RAW and then opened into Photoshop, then Windows reports it as modified, even if no changes were made.

            Did you save or close the jpg without saving?

            • 3. Re: Modified JPEG
              conroy Rockstar

              Mr_Pedantic wrote:

               

              My question is does this behaviour result in the image being resaved with a loss of quality each time that it is opened this way?

               

              No. Camera Raw will write metadata into a JPEG without resaving and degrading the image. However, if you then save JPEG from Photoshop, that will result in degradation.

              1 person found this helpful
              • 4. Re: Modified JPEG
                Mr_Pedantic Newcomer

                I closed the JPEG without saving. Windows still reports it as modified.

                • 5. Re: Modified JPEG
                  conroy Rockstar

                  Mr_Pedantic wrote:

                   

                  I closed the JPEG without saving. Windows still reports it as modified.

                   

                  Like I said, Camera Raw will have written metadata into the file without resaving and degrading the image. You can do a little experiment to prove that the image in the file won't be changed by Camera Raw. Hint: Photoshop can difference layers.

                  • 6. Re: Modified JPEG
                    Rockstar

                    Mr_Pedantic wrote:

                     

                    …Windows still reports it as modified.

                     

                     

                    That doesn't matter.  If you just closed the file without saving, no compression or recompression took place.

                    1 person found this helpful
                    • 7. Re: Modified JPEG
                      Mr_Pedantic Newcomer

                      Thank you to those people that replied to my question.