Corrupt catalog, corrupt preview file?? Help!

[Jxbrrd]

I think I have a corrupt catalog in Lightroom Classic on a Mac, and perhaps a corrupt preview file.  Sometime in the last couple of months, it became impossible to access images.  When I open lightroom, I only see grey rectangles in Gridview.   I have imported photos to lightroom for years from a number of 2 gB hard drives and you still can see the hard drives listing the photos for each day in the library catalog.   Occasionally, you can see the images from a few of the drives.  But you can no longer see most of the images anymore.   (The actual dng files are still on the hard drives.)

                  When I tried to optimize or save the catalog using LR 14.01, it would just hang.    So I went back to a previous version of LR (13.3.1), I can open some of the older catalogs, but they still seem corrupt, ie still just see grey rectangles in grid view.  I have read that it could be just a corrupt previews file and you should delete this file and it will “rebuild” but this sounds a little sketchy.  The previews files that I have are large(17-35 gB)  If I delete that huge file, how will it rebuild by itself?

I was hoping to go back using Time Machine, to an earlier version of the catalog(there are many zipped “older catalogs from previous updates) and find an earlier version of my catalog that works with an earlier previews file.   But I am not certain which files to pull…

• What are the essential files to open LRC(eg .lrcat, Previews.lrdata, helper.lrdata?)

Hopefully I can pull these files from Time Machine at a time when the catalog was working and then I can upgrade from there.   I have to match an older catalog to a version of LR that can open that catalog but I think each catalog will identify which version it comes from.

Or if anyone else has any great ideas for figuring out and fixing this problem it would be greatly appreciated.   To reimport all those photos to a new catalog is possible, but it will take months and months of work, not to mention losing all the modifications on many of the photos and I keep thinking that since it was working a few months ago, I should be able to backtrack to a working catalog with previews.

Please ask questions if my explanation is not clear.  I can post screen shots if that will help.                                                                                  Thanks MR

[dj_paige]

When I open lightroom, I only see grey rectangles in Gridview.

Try this: https://www.lightroomqueen.com/how-do-i-change-my-monitor-profile-to-check-whether-its-corrupted/

[Per Berntsen]

I have read that it could be just a corrupt previews file and you should delete this file and it will “rebuild” but this sounds a little sketchy. The previews files that I have are large(17-35 gB)  If I delete that huge file, how will it rebuild by itself?

The previews will rebuild as you browse folders in Library.

Alternatively, you can click on All Photographs in the Catalog panel, select all the files (Cmd + A), then go to Library > Previews > Build standard size previews. This will take some time, so you might want to let it run overnight.

Before you do this, try changing the monitor profile (might be called display profile on a Mac) as advised by @dj_paige .

If it doesn't fix the issue, delete the preview cache.

If that doesn't help either, try restoring a backup catalog.

I was hoping to go back using Time Machine, to an earlier version of the catalog(there are many zipped “older catalogs from previous updates) and find an earlier version of my catalog that works with an earlier previews file.   But I am not certain which files to pull…

• What are the essential files to open LRC(eg .lrcat, Previews.lrdata, helper.lrdata?)

Hopefully I can pull these files from Time Machine at a time when the catalog was working and then I can upgrade from there.   I have to match an older catalog to a version of LR that can open that catalog but I think each catalog will identify which version it comes from.

The best way to restore a backup is to use a regular backup created by LrC, rather than using Time Machine.

LrC backup catalogs have had their integrity checked, and are optimized.

The essential files are the ones that are backed up – catalog file (.lrcat) and the .lrcat-data folder.

Unzip the backup, then copy these two items to a folder of your choice. Double-click the catalog file to launch LrC.

I take it that you have let LrC create backups regularly?

One more thing – do images display properly in Develop?

[Jxbrrd]

Thank you all for your suggestions.I have multiple backups.  Have tried at least 10 of them, dating back months and months to when the program was working normally and I could view all previews without the hard drives with the photos connected to the computer.  Despite installing the back ups, the previews are not there(do they require a separate file?) and the program does not go back to where it was before.   Should the installed back up allow me to see the previews?

[dj_paige]

Should the installed back up allow me to see the previews?

No. Not if it is caused by a corrupt monitor profile. Did you try the instructions at the link I gave?

[dj_paige]

Adding, it seems you have somehow concluded that the catalog is corrupt. Did you actually get an error message saying that the catalog is corrupt?