How to keep thumbnails

[Dheaton]

I have some photos that I use on an external backup hard drive.  When this drive is not connected I can not see any thumbnails.  When I connect the drive I see all the thumbnails appear.  Is there a way to always have the thumbnails show even when offline?

[Neox99]

No!

That would be like asking to read a book without opening the covers or watching TV with the power off.

[Just Shoot Me]

You can built Smart previews for all those images on the external drive.

[Jim Wilde]

dheaton  wrote

I have some photos that I use on an external backup hard drive.  When this drive is not connected I can not see any thumbnails.  When I connect the drive I see all the thumbnails appear.  Is there a way to always have the thumbnails show even when offline?

Yes, you should be able to see thumbnails and images in the Library module when the original files are offline (Library only shows previews of the originals). So unless you haven't yet built any library previews, you should be seeing the images in the Library module.

Suggest you start Lightroom with the external drive connected, then select a bunch of images and do Library>Previews>Build Standard-sized previews. When that's finished, close Lightroom, disconnect the external drive, restart Lightroom and you should be able to see the thumbnails and full image in the loupe in the Library module.

If that's not happening there may be something else going on that we need to try to figure out.

And if you want to be able to EDIT the images while the drive is offline, you'll need to as as @Just Shoot Me stated and build Smart Previews.

[davidKheaton]

Thank you for your answers and help.

I should have stated that some of the images on external hard drive have thumb images when it is not connected but not all of them.  I was wondering if there is a feature somewhere that says to delete thumbs after a certain amount of time..  I will try the above answers and see how that goes.  Thanks so much.

[Jim Wilde]

You probably need to look closely at those blank thumbnails when the disk drive is online. Generally, any image that doesn't already have a preview when it appears in the Grid will immediately have the preview automatically built, i.e. if the image file is available, blank thumbnails should be "fixed" automatically. However, if that doesn't happen, it may be that even though the drive is online LR still shows the file as "missing". So, with the drive online, check the thumbnail of one of the blanks to see if there's an exclamation mark in the top-right corner of the thumbnail (which would indicate a missing file).

[Just Shoot Me · Accepted solution]

That is because LR only keeps standard previews for a period of time. Then they are replaced with different ones.

This is something that is not adjustable. So as soon as you start to add or browse newer images the standard previews for older images are replaced by ones for the newer or newly browsed images even if the newly browsed images are older and LR has access to the original file.

That is why some images have them and other don't.

So you have 2 options when this happens.

1) Connect your external drive so LR can read the original file and create a preview for it.

2) Build Smart Previews for all the images that are in the external drive. But doing that will take a lot of disk space on your internal drive.

If you have the external connected and you are browsing images in the Library module Grid view or in the film strip and you see 3 white dots in the upper right hand corner of the thumbnail that is a sign that LR is creating a standard preview for that/those images.

With the external disconnected and LR doesn't have access to the original file then you get a blank gray box where the image would normally be displayed.

[Jim Wilde]

https://forums.adobe.com/people/Just+Shoot+Me  wrote

That is because LR only keeps standard previews for a period of time. Then they are replaced with different ones.

This is something that is not adjustable. So as soon as you start to add or browse newer images the standard previews for older images are replaced by ones for the newer or newly browsed images even if the newly browsed images are older and LR has access to the original file.

I think you might be confusing the Library Previews cache with the ACR Cache. The latter, which is only used in Develop, does operate on the basis of throwing out older cache entries if the user-set size of the Cache isn't big enough for new entries. The ACR cache is used to pre-load the image in the Loupe window in Develop while the new full preview is rendered in the background.

The Library Preview cache does not have a user-set size limit, it keeps on growing as required. It will normally contain a preview per image (there's no ageing involved, so they are never completely thrown away on that basis). Each preview consists of a "pyramid" of different size jpegs of the image, the 1:1 preview being the largest, followed by Standard, followed by a range of thumbnail-sized previews for things like the Navigator window, Filmstrip thumbs, Grid thumbs, etc.. The only preview that the user can control would be the option to discard 1:1 previews on an age basis, but there is no user option to discard the rest of the preview pyramid for any particular file. Standard-size previews (if not already rendered) should always be created when the image appears in the Filmstrip or the Grid or the Library Loupe, and the only circumstances that I can think of to explain the issue of them not automatically being created is if the original file is missing or offline, or if there's a corruption of the Preview Cache itself. Hence my question to the OP.

Smart Previews won't really help, other than as a diagnostic.....they are only used in the Develop module, not in the Library. If one can be created, that would rule out missing or offline files, and thus would point to Preview Cache corruption.

[davidKheaton]

if my external HD is connected all the thumbs show.  When the external HD is disconnected only some of the thumbs show.  I took 10 images that did not show and told LR to rebuild previews and it did.  When I again disconnected the external HD those images are still not shown.  I don't really understand why.

[Jim Wilde]

davidKheaton  wrote

When the external HD is disconnected only some of the thumbs show.  I took 10 images that did not show and told LR to rebuild previews and it did.  When I again disconnected the external HD those images are still not shown.  I don't really understand why.

Just to confirm, you did reconnect the HD before you tried to rebuild the previews, yes? Normally you couldn't rebuild a preview if the image is offline, but I just wanted to make sure what you did in case there's a bug there.

So assuming you did reconnect, and all the thumbnails were showing, what type of previews did you try to build for those 10 images?

And all of this activity is in the Library module, yes?

One thing that would be worth trying: close Lightroom, then using Finder/File Explorer go to the folder containing the catalog and rename the associated "catalogname Previews.lrdata" (ignore the catalogname Smart Previews.lrdata if it exists). Restart Lightroom with the HD connected first, all the thumbnails should initially be blank but should then start to populate. If not already on screen, scroll to those 10 images that you used earlier....again the thumbs will be initially blank, but should populate quite quickly. Select the 10 images and build 1:1 previews, when that's done, close Lightroom. Disconnect the HD, restart Lightroom, are the thumbnails still showing for those 10 images?

[Just Shoot Me]

Don't know.

I keep my images on an internal drive so they never go missing so I've never run into this.

[Jim Wilde]

I've not run into either, and my images are on an external drive. Even if I disconnect it, I can still see the thumbnails/previews (as should be expected).....so I'm beginning to think in terms of a preview cache corruption.

[cmgap]

Do you have Generate Previews in Parallel checked in Preferences > Performance?

[davidKheaton]

Yes, that is checked.  Should it be?

[Just Shoot Me]

When you were generating the previews did you notice the 3 white dots on the images and did you wait until those dots had gone away before you disconnected the drive?

[davidKheaton]

Yes the previews were all built.  When I disconnect the drive I then have a ( ! ) on each file but the preview is still visable. Doing this seems to keep the 1-1 previews even when the HD is offline.  So I have done this to about 20 images now.  With the HD connected I tell it to build 1-1 previews and I get a window that says " No 1-1 previews were built.  All 1-1 previews are up to date."  The same thing happens when building standard previews.  Does that mean that there is something wrong with my catalog previews?

[Jim Wilde]

davidKheaton  wrote

Yes the previews were all built.  When I disconnect the drive I then have a ( ! ) on each file but the preview is still visable. Doing this seems to keep the 1-1 previews even when the HD is offline.  So I have done this to about 20 images now.  With the HD connected I tell it to build 1-1 previews and I get a window that says " No 1-1 previews were built.  All 1-1 previews are up to date."  The same thing happens when building standard previews.  Does that mean that there is something wrong with my catalog previews?

That sounds as though the problem is fixed. Did you rename the old previews folder as I suggested earlier?

[davidKheaton]

I was only doing this on 10 images at a time.  Is there some way to do it to all files that have no preview when HD is offline?  I do not want to keep smart previews or even 1-1 just standard previews.

[Jim Wilde]

davidKheaton  wrote

I was only doing this on 10 images at a time.  Is there some way to do it to all files that have no preview when HD is offline?  I do not want to keep smart previews or even 1-1 just standard previews.

Yes you can build Standard or 1:1 or Smart previews for the entire library if you want to. But one step at a time, I'm still waiting for an answer from my earlier question: did you rename the original previews file as I suggested, and if you did does the problem seem to have been fixed on the files that you tested?

If the answer to both those questions is "yes", then that would strongly suggest a corruption in the original previews cache. In which case simply delete the renamed previews file, it's of no value if it's corrupt. Lightroom has already created a new one, and if you take no further action Lightroom will start to rebuild standard previews for all your files, but only as an when an image appears in the grid or filmstrip, i.e. it doesn't do that automatically for images which are "off screen".

So you could simply leave things as they are, but that's not a great interactive process if every time you bring an image on screen, which has no existing preview, there's a slight delay while the standard preview is automatically built. Perhaps a more sensible approach would be to select say the last 12 months images, select all, then choose to build standard previews for those. Leave it running until done. Then you can either leave things as they are, i.e. all recent images (and new ones) have the preview, older images will give a slight delay when loading, or do an overnight select all photographs and build standard previews procedure.

[davidKheaton]

Thank you for your reply

I did not do all that you were talking about because honestly I didn't completely understand but I now think I do.  I just selected all of 2017 images with the hard drive connected and told it to build 1-1 previews and that is in process still.   If that does not fix all of the standard preview issues then I need to start with what you have suggested above.  That would have been a better way to go as it would help narrow down the issue.  Thanks for your help, I really appreciate it.

[Jim Wilde]

  wrote

Yes, that is checked.  Should it be?

It shouldn't make any difference.

[davidKheaton]

I just noticed that in the catalog settings I have discard 1to 1 previews after 30 days.  I have this set this way because I didnt' need the larger images all the time.  Would that be the cause of my thumbs going away?  I thought that the smaller preview would be there all the time even when on a disconnected external HD

[Jim Wilde]

davidKheaton  wrote

I just noticed that in the catalog settings I have discard 1to 1 previews after 30 days.  I have this set this way because I didnt' need the larger images all the time.  Would that be the cause of my thumbs going away?  I thought that the smaller preview would be there all the time even when on a disconnected external HD

Not relevant. If the preview system is working as designed, discarding the 1:1 still leaves the rest of the preview pyramid intact.