Cache purge in latest Lightroom Classic release

[GavinI]

Lightroom Version

11.4.1

Operating System

1. macOS 12 Monterey

My previews cache is now north of 4GB and my Freefile Synch backup app is crawling through it. Earlier releases of Lightroom had a cache purge option, but it seems to have disappeared with the new release, and perhaps even earlier releases where I hadn’t noticed the change..

Is it no longer possible to perform a purge? Or is Adobe implying that we no longer need it?

Thanks for any advice.

 

[Woodbutcher]

LrC now automatically removes previews for deleted pictures which keeps the file from increasing and never decreasing. It didn't use to. You can delete the preview file and it will get recreated, but in your case, I'd just set my backup tool to ignore the file. There is no reason to save it since it is just a cache.

 

[Johan Elzenga]

AFAIK, previews of deleted images were always removed, or at least that is what should have happened. What is really new is that Lightroom now also removes ‘out of date’ previews. These are previews of images that have been updated, so the preview needs to be re-rendered, but that hasn’t happen yet for whatever reason. One example is when you apply a preset to a large selection of images. Only those images that are visible in the grid at that time will get an updated preview, images that are ‘out of sight’ won’t.

 

[GregJ]

You guys are losing me here. LR deletes previews from the preview file storage location when you delete an image and always has (I thought). And what do you mean by cache? Cache is in memory and preview files are files stored to disk - preferably in the same folder as the catalog and same disk as the LR program filers. Maybe I'm misunderstanding.

There was a thread on this recently where I was debating whether or not just to delete my whole previews folder. Mine is way bigger than yours. It is 490 GB! I generate 1:1 for every image and I have high-res raw files. But I thought, why do it? I have plenty of space.

By the way, I should know this but I don't.... When I back up my catalog, it is not rewriting that whole huge preview folder every time? No way ... because my backups go fast and each backup is a standalone document created new each backup. If the huge preview folder was rewriting every time it would take forever.

 

[GregJ]

Clete, Jim, Johan....
Here is a snapshot of my LR Folder. I don't care about old cat versions or anything but for the latest version of LR. What can I get rid of here? Tell me what to delete....

 

[Hal P Anderson]

The previews folder is called a cache. A cache doesn't need to live in RAM. Lightroom also has a "Camera Raw Cache". That also lives on disk, and I suspect that the OP was referring to that when he asked about a "purge cache" button.

When you back up your catalogue, the previews don't get backed up. Neither do your images.

For your question of what you can delete, anything in that listing that doesn't contain "v11" is fair game.

 

[Woodbutcher]

My post was in reference to Automatic Preview Purging described here: https://www.lightroomqueen.com/whats-new-in-lightroom-classic-11-4/

My preview file went to ⅓ the previous size after upgrading to 11.4.

 

[GregJ]

The previews folder is called a cache. A cache doesn't need to live in RAM. Lightroom also has a "Camera Raw Cache". That also lives on disk, and I suspect that the OP was referring to that when he asked about a "purge cache" button.

When you back up your catalogue, the previews don't get backed up. Neither do your images.

For your question of what you can delete, anything in that listing that doesn't contain "v11" is fair game.

Thanks Hal. I don't understand why they call a disk with files written on it a cache, but whatever.... It's a folder full of files. Anyway, I'm an idiot for asking if the preview files were backed up as part of the LR catalog backup function (when you exit or tell it to). My preview folder is huge and my cat backup folder is way smaller. You can't really peek in those so it's hard to know what is in there. And of course, the image files are not backed up as part of that function. I have 6TB of raw files! LOL.

OK,, so you are telling me I can delete all of that stuff except the ones with V10-V11. I'm doing it. I also found some even older catalogs scattered around my drive. Gone.

 

[GregJ]

My post was in reference to Automatic Preview Purging described here: https://www.lightroomqueen.com/whats-new-in-lightroom-classic-11-4/

My preview file went to ⅓ the previous size after upgrading to 11.4.

I misunderstood. Thanks. Learned something here.

 

[Johan Elzenga]

And what do you mean by cache? Cache is in memory and preview files are files stored to disk

Cache is temporary storage, which can be in memory but also be on disk. Your computer probably has thousands of cache files, from apps like your internet browser to camera raw.

 

[GregJ]

Johan, please.... Come on Man.... This is me you are talking to. I've been building PCs since there was a PC.
Anyway, I know all about caches since I'm a computer clean-freak. I guess I can see why LR would call it a cache because LR creates the preview files so that the library module runs more smoothly and faster, but sill ... It's a folder full of jpegs and as a photographer, a folder full of jpegs is a folder full of jpegs.

I think I'm gonna delete my half-terrabite big preview folder just for fun.... It might give me some form of strange satisfaction.
It might be the only fun thing I do in LR right today since I'm plodding through hundreds of raw files I shot in Mexico trying to name and key word them. Boring.... Oh, and I'm going to create 1:1 previews for them on import to the PC... LOL.

By the way ... when I move my files and their edits from my laptop to my PC today and do it the right way vs my normal way (you followed that conversation so know what I'm talking about) and I export to catalog and then import to my PC, will the 1:1 previews I built for that folder on my laptop copy to the PC, or will LR build them again on the PC as part of the process? I would think it would just copy the preview file along with the raw vs generating another preview jpeg, right? I'll know soon enough because if my PC regenerates them my CPU will crank to full overclock and my fans will start ripping....

 

[Johan Elzenga]

Johan, please.... Come on Man.... This is me you are talking to. I've been building PCs since there was a PC.

That doesn’t change the fact that a cache can be hardware or software: https://en.wikipedia.org/wiki/Cache_(computing)

 

[clee01l]

That doesn’t change the fact that a cache can be hardware or software: https://en.wikipedia.org/wiki/Cache_(computing)

Going to the dictionary Cache: a collection of items of the same type stored in a hidden or inaccessible place.
"an arms cache".
In the computer lingo the same type refers to the same type of data.


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