13 Replies Latest reply on Oct 30, 2008 7:24 AM by (xbytor)

    Changes in XMP adds  History?

    shootRAWsmart Level 1
      I've heard that Lightroom saves "History Tags" in the XMP data now, and have seen some different things in the File Info that would suggest that, to some degree, history is indeed now written into the file...

      Is this true, and how does it apply in practical use? Does this mean we can save the file history now, or will be able to soon?
        • 1. Re: Changes in XMP adds  History?
          Level 1
          Nope...it does save snapshots but not history. That's a Lightroom database property only.
          • 2. Changes in XMP adds History?
            Level 1
            Jeff_Schewe@adobeforums.com wrote:
            > Nope...it does save snapshots but not history. That's a Lightroom database property only.

            FWIW, Ps does have this ability. Looks interesting but I don't have a need for
            it in my workflow.

            -X
            • 3. Re: Changes in XMP adds  History?
              shootRAWsmart Level 1
              Can you tell me how that works? (...or point me in the right direction)
              • 4. Re: Changes in XMP adds  History?
                Level 1
                In Photoshop's preferences, turn on History logging and choose either a separate log file or in the xmp or both...
                • 5. Changes in XMP adds History?
                  Level 1
                  Jeff_Schewe@adobeforums.com wrote:
                  > In Photoshop's preferences, turn on History logging and choose either a separate log file or in the xmp or both...

                  It's also write-only metadata. You can't change history. Trust me. I've tried.

                  -X
                  • 6. Re: Changes in XMP adds  History?
                    shootRAWsmart Level 1
                    wow that's crazy!

                    Now, just so I understand this... this was true of CS3 as well, nothing new here with CS4?
                    • 7. Re: Changes in XMP adds  History?
                      Level 1
                      >this was true of CS3 as well, nothing new here with CS4?

                      Longer than that...either Ps 7 or CS was when History logging was put in.
                      • 8. Re: Changes in XMP adds  History?
                        shootRAWsmart Level 1
                        nice! Thanks for the help...
                        • 9. Re: Changes in XMP adds  History?
                          shootRAWsmart Level 1
                          OK, I messed around a little and naturally, a few more questions came up.

                          Am I correct that the History Log in Photoshop is really only a way to track and see the history, not really to use or go back to a previous state once a file is saved and closed? This Adobe help page would suggest that: http://tinyurl.com/5az2m4
                          and besides, I can't figure out how it works if it does... :)

                          So, as far as Lightroom goes, is there a History that persists after the file is saved and closed?

                          I'm looking back at the way I asked the question, what I meant to ask was, can you save a history, and go back to states in that, that persists past the saving and closing of the file, through the metadata?
                          • 10. Re: Changes in XMP adds  History?
                            Level 1
                            >Am I correct that the History Log in Photoshop is really only a way to track and see the history, not really to use or go back to a previous state once a file is saved and closed?

                            Correct, the History Log has zero to do with the History feature inside of Photoshop...and once a file is closed from Photoshop, the History "feature" (including events and snapshots) are lost. You CAN save out Snapshots as separate files and do a reconstruction but the actual history steps are gone.

                            The reason fo this is that while the History Log makes a record of the "steps" as you do them, the History feature records the actual pixels and only shows the steps. If you click on a history event or snapshot, you see the PIXELS that were there at that event or snapshot.

                            This is completely different in Lightroom as Lightroom's history is more like the History Logging in that it doesn't store the actual pixels but only the edit list. Which means Lightroom's is arguable a bit more modern. Both Photoshop's History feature and Lightroom's History feature were done by the same guy, Mark Hamburg. But the implementation was different...

                            Seriously, you would NOT want to store all the history events and snapshots inside an actual file unless you would be willing to tug alone a HUGE additional (potentially) bunch of extra pixels...the Photoshop History Logging only store a small amount of metadata and not all the pixels which is why it can be stored in .xmp. Lightroom's History is only stored in the LR database, not in the file either. But the LR History is also only lightweight metadata.
                            • 11. Re: Changes in XMP adds  History?
                              shootRAWsmart Level 1
                              right right... makes perfect sense, especially about the "overhead". I had the wishful thinking goggles on for a moment, that the XMP special sauce could do a minor miracle.

                              Thanks so much for the discussion... I learned a lot.
                              • 12. Re: Changes in XMP adds  History?
                                PECourtejoie Adobe Community Professional
                                The history log feature is a key instrument in forensics/law enforcement.
                                Xbytor: even with a text tool? is there a checksum somewhere?
                                • 13. Changes in XMP adds History?
                                  Level 1
                                  PECourtejoie@adobeforums.com wrote:
                                  > The history log feature is a key instrument in forensics/law enforcement.
                                  > Xbytor: even with a text tool? is there a checksum somewhere?

                                  I needed to do it from a script from within PS which is why it didn't work. I
                                  imagine that extracting the XMP, modifying it, and then reloading it would but
                                  doing those steps in PS is not possible either on an open document. My need here
                                  was to annotate the History Log with additional information.

                                  Another option (if the document is closed) is to use the XMPScript extensions.
                                  This would work from Bridge or from PSCS4.

                                  I don't recall there being a checksum in there, but if there is, all bets are off.

                                  -X