recover deleted previews

[Dan Lamont]

Hello Folks:

I am runing Lightroom Classic 10.0 on a Mac running Catilina10.15.7

A few days ago I was trying to sync a collection in my Publish services to my Smugmug portfolio. I screwed up and ended up deleting all the previews from my catalog (lessson: never start such a project in the eveing after a glass of wine). 

I know the previews will come back if I browse each of the folders in the catalog BUT things get interesting because the catalog contains 329,000 images shot since 2003 spread across 19 hard drives. Browsing each folder would take until I die or beyond. 

Can I import the old preview file from a previous backup? If so how do I do this (without cause more problems)?

Any wisdom and experience would be hugely appreciated!!

Thanks

Dan

[Ian Lyons]

Select the folder(s) you need to build previews for, then choose 'Previews > Build Standard-Sized Previews' from the Library menu

[dj_paige]

What @Ian Lyons said, and then let it run overnight and maybe the next day as well.

[Rob_Cullen]

"...deleting all the previews from my catalog..."

These words have me worried that you deleted the (Preview) thumbnails in the Catalog Library Grid.

If you 'deleted' the file ending  .LRDATA using the OS, then the correct answer to your queation is as given by @Ian Lyons and @dj_paige 

If you really did delete from the Catalog Library, then you have a bigger problem!

If you "Removed" thumbnails- you would need to restore a Backup Catalog.

If you "Deleted from Hard-drive"- you would need to restore image files from a backup, and restore a Backup Catalog.

[Just Shoot Me]

I agree with WobertC.

I Delete Preview, actually the whole Previews folder, from time to time.

LrC will just Rebuild them.

But If you deleted the thumbnails shown in the Grid View and selected Delete from disk in the dialog box that comes up you have actully Delete the REAL image files from your Hard drive.

If you haven't Empied the trash, Recycle Bin they can be recovered. What can't be recovered is any edits you did to them. LrC has removed them from the catalog. But if you had the option to Auto Write changes to XMP them might be recoverable.

[Eric Pec]

You can try. You can also restore everything from a backup. This is one of the purpose of backup.

Best Regards
Éric Pecquerie
Sent from Eric's IPad Pro

[Just Shoot Me]

Not sure what you mean by Backup. If you are referring to the backups of the LrC catalog that by default is prompted to make once a week by default that is only the Catalog file that is backed up. No images are included in that backup.

If you are suggesting that the Original Poster made, or makes, regular backups of all their image files well in my experience that RARELY ever happens and then when someone does delete image file by mistake they always come here asking why LrC doesn't do that.

[Dan Lamont]

Thanks for all the thoughts but I'm still in the dark. For the record I back up all my images onto multiple drives. That's not the issue. I've refined my description of the problem and include it below with the hope one of you more adept souls can see through the haze that alficts me on this problem.

I use Smugmug as my web portfolio platform. Using the Smugmug plugin in Lightroom I intended to sync my portfolio galleries on my Smugmug site with the associated folders in my Publish Services feature in Lightroom. 

I THINK what I did was instead of just syncing “Folders and Galleries” I failed to unclick the “sync photos” check box. I went away from the computer for dinner. Returning hours later I discovered that Lightroom was still syncing, when it should have been done with the small job in a matter of minutes. Lightroom, which in my case contains 330,000 images, was attempting to link all those images with Smugmug, where I have only a couple of thousand images (a couple of hundred in my portfolio and most in client web galleries). It seems that the process any thumbnails from Lightroom that did not have a counterpart in Smugmug were removed .

I’m using bare drives in docks. When I open Lightroom I can see the previews ONLY for the image files on the specific drives that are installed and running.  I can’t see the previews (ie preview.lrdata) for  image files that are on drives not installed and running. So where are they and how can I see them when the drive is not installed and running ?  With so many images and drives I really need to be able to see the previews all the time so I can find older images when needed without constantly stuffing hard drives in and out of the docks. This all used to work just fine... argh.

When I tried the command to make new standard previews,  (hoping that would somehow resurrect my previews.lrdata) as Ian suggested above LR tells me that they already exist and are up to date. This makes me assume the previws still exist. Why they won't show up as they used to regardless of whether or not the source drive is installed and running is a mystery to me. My question is how do I get them back? Should I bring in a backup version of the previews.lrdata to resolve this issue? If so what is the process.

When I go to open the backup Lightroom wants to update to the latest version and won’t let me do anything unless I comply!! I don’t want to do that for fear such and updat will just complicate matters.

Does all this make sense to any of you, my respected colleagues?

Many thanks,

Dan

[Rob_Cullen]

I have not used SmugMug, and so am at a loss to help with an answer, but yet make some more comments (hopefully helpful.)

The SmugMug Plugin, and Publish Services, are 'Export' facilities that export derivative copies of the original files - I would think that the original files (on various hard-drives) would have needed to be connected for the 'Export' for function. (Except maybe if you use 'Smart Previews' )

When you say "I can see the previews ONLY for the image files on the specific drives that are installed and running."-

Do you see any grey thumbnails for un-attached drive images?

The function to re-build previews (Standard, 1:1, Smart) requires that you DO see thumbnails (of some kind), AND that the original files (on external drives) are connected to the computer (in your dock).

Do you NOT see any thumbnails at all for photos on external drives? (the "Mystery")

This would suggest that the Previews have been 'Removed' from the Catalog (along with any edits, etc), and only a restore of a Backup Catalog will be helpful. Do not be concerned about the v10 Catalog update prompt- But- Copy a Catalog from a Backup zip to a separate folder (other than your current catalog) open this copy and allow it to update for v10. Again! The external drives will need to be connected (all 19!) to allow Previews to re-build from data in the original files!

As stated by @Just Shoot Me  the Previews.LRDATA Cache is not backed up with a Catalog Backup- so no possibility to 'restore' a

Preview cache.