When selecting that option all edits will be written to a XMP sidecar file located in the same folder, or folders, as your images. Before all edits were stored in the LR catalog file. So LR is asking if to Write your edits that were originally stored in the catalog file to the XMP file or to Read the existing XMP file. you want to Write Changes to Disk not Read from them.
You can select multiple images, or all images (that is not suggested, to SLOW), and then click the exclamation mark to do that group of images at the same time.
Honestly I always Check that option, or check that it is selected, at the first startup of a new version of Lightroom. Not sure why anyone would store edits in the catalog file.
Ok. I think I understand the concept and how it works. There is no sidecar files here though. I use DNG, TIFF and JPG's exclusively. Those have the sidecar files or metadata inside the files. I have some older pictures in RAW format, and those HAVE sidecar files. So, I know Lightroom writes the data. However, the newer files I'm working on keeps coming back with the same excuse of external changes.
Last night I selected my whole library and hit ctrl + s. That should have fixed the problem. And it did for a short time. Some minutes and hours later, most of the pictures had the same problem again. It does not matter how often I save the metadata or in what way I do it. There are something triggering some changes in the files! There should be no backup on the SSD disk or SAN, there should be no preview stuff from windows, there should be no user created changes. I can not figure it out for the life of me!
OK but with DNG the edits still have to be Written to the DNG file instead of being stored in the catalog file.
XMP files are created by LR and the Adobe Photo downloader program when the image files are copied to your HDD from either a camera or memory card in a reader. Even if there are no edits applied.
By Default LR stores all edits for all types of files in the Catalog file. That is unless that XMP option is checked. Yes it is very misleading. That option says Write changes to XMP when it really mean Don't Write change to the catalog file and instead write them to either the file itself, with certain file types like DNG, or a Sidecar XMP file.
I know what it does. I'm quite familiar with the concept form other programs. And by the way, when XMP file option is check it Lightroom stores the metadata in files AND the catalog. Anything else would be highly irresponsible. I do not know this for a fact. I don't know the lightroom code. But I would be HIGHLY surprised if I'm wrong. Reading only metadata from the xmp or image files would be counter intuitive. It would take a lot of time and make the program slow as snails. Especially on regular hard drives. The xmp option if only there for other apps to more easily read the metadata, and incase of catalog disaster. Metadata from a catalog is one of the few ways a program can do certain operations effectively.
That still does not explain why this happens. Why does the external changes trigger? I have literally NO idea. Yesterday, I thought it might be that is just takes time to write all the data to all the thousands of images. I got the notification that the XMP data was still written when I tried to quit Lightroom. So I left it over night to finish the job. But I still have tons of images with external metadata changes. When I forse LR to write the data, it seems to take anywhere from 15 to what ever minutes before the changes is a fact again.
Any ideas to solve this would be great!
If you are writing to XMP, or DNG the information is still stored in the catalog. So having metadata in both places is an extra security step and useful when sharing files with other people who need to work on them.
I disagree with the replies above. If you have the edits stored, written, to a XMP there is no need to also keep them in the catalog file.
Same goes for the default behavior of LR storing, writing, those edits to just the catalog file.
If that option isn't checked then the only program that can Read/See the edits you have made is Lightroom. If you write them to the XMP, or actual raw file (DNG), then if you open that raw file in ACR those edits are read and applied.
Spud80, Whatever. Have it your way. I'm done trying to explain why you are seeing the exclamation mark.
Guys. We are all pretty much agreeing here. Bond does not believe the catalog stores all the information if that option is ticked, two other persons do. Let's just leave it at that. I don't care. We kind of know how these settings work. I'm not trying to be condescending, but this is NOT the actual problem, and therefor pretty uninteresting as far as this tread goes. I need to write the metadata to xmp or the image files, because I like the extra security and being able to use other programs with the metadata. That's it.
That leaves us to the real issue at hand. I'm constantly being bugged about something changing OUTSIDE of Lightroom. And I can not understand what it is.
Shootistbond007, you have done no such thing as explaining why this is happening. You are explaining how meta data is written and stored, and I already knew that.
If you somehow were trying to explain to me why I see this external change notifications, then I'm afraid you have have done a very poor job.
Please try again. I need to have others with suggestions here, because I'm totally lost.
Since LR has no way of telling us which fields contain metadata conflicts it is almost impossible to give a definitive answer other than to make the message go away. See reply #2 in this similar thread:
That does nothing in my case, I'm afraid. I already only use the "Edit in" commands from within Lightroom. May it be Photoshop NIK colleciton or something else. Problem is that this does not only appear on photos I edit in other applications. It happens to virtually ALL my thousands and thousands of images. So, I can not simply make it go away that way.
And if I choose to save the data to xmp for all my files, which I did one night, they are all there again the next day! So, something system deep is changing something in this files. Nothing to do with me doing anything to the files. At least not directly. This is a pretty clean Win 7 computer with mainly Adobe programs and the Office suite.
If we COULD see what exactly had changed, it would be a lot easier to pinpoint what's changing the files. But I have not any idea how to do that either. Tried to download ExifMeta plugin from Rob Cole, but his site is still down.
What other program or programs are you using that access your image files?
Oh man! I believe I have found the culprit. This is rather embarrassing.
My SAN consists of two raid arrays. I have not touched this application in about two years, but there is a sync program called "Super Flexible File Synchronizer" running, and syncing everything between the two volumes. I just forgot about it as it's been running in the background for so long. It's rather obvious that this program has to set some kind of archiving or copy flag on the files so it does not have to compare it to the destination data all the time. At least I suspect something like this is the case.
Another reason why I did not think of my server for so long was because I was pretty convinced that also my local workstation images had the same issue. But as I were working on my local images for several hours yesterday, I did not see any external change warnings. So, it might have been a one time thing for the local files once I started using the xmp feature. Maybe I just imagined it. I don't know.
I'm pretty certain that the software on my server are to be blamed though! I'll update the thread once I can verify it. Not sure that this will solve my problem though. As I'm pretty dependent on that file sync system. Perhaps I'll look for some system that does not change any attributes or metadata. Perhaps there is a way to prevent this from happening in the program. We'll see.
Thanks a lot for trying to help out! Without this thread and your questions I'm pretty certain that I would still be in the dark...
Having the same issue exactly, but I suspect Time Machine or Backblaze backup might be to blame..or not. Really, I don't know. It's a bit annoying.
I didn't ever experience this until i upgraded to Lightroom CC. :/