Lightroom: Controls for limiting the catalog previews file

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  • Updated 3 years ago
  • (Edited)
I’ve seen LR catalog preview files (not smart previews) ballon up to ~75GB where performance takes a big hit. While we can limit the Camera RAW and Video caches, we don’t have controls for limiting or managing this Previews file size. Even deleting all the 1:1 previews and optimizing the catalog doesn’t bring the file size down significantly. Our only option appears to be to delete this file manually and let LR create new previews.

Perhaps we need automatically discard the standard previews after a period of time just like we have with 1:1 previews? Or perhaps Lightroom could automatically prune previews intelligently so that users don’t realizing that its happening?
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Scott Martin

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Posted 4 years ago

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Rob Cole

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Hi Scott,

If deleting all the 1:1 previews does not bring the "file size" down significantly, then you probably have the size of your *standard* previews set too large.

The reason for this is highly technical and non-intuitive, but try this:
* drop down the size of your standard previews by a notch (or two..).
* delete ALL previews (since otherwise standard previews won't be rebuilt at the new size).
* rebuild 1:1 previews (which rebuilds standard previews too).
* look at directory size.
* discard 1:1 previews.
The preview folder should be substantially smaller now.

To be clear: the savings is NOT just that standard previews are smaller, but that Lr won't actually discard 1:1 previews if standards are too big - strange but true (and 100% sensible once you understand the details of Lr preview subsystem design).

Cheers,
Rob
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Scott Martin

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Hey Rob! While I'm experiencing this on my own system, I've also seeing this on a number of my clients machines as well. In all cases, we're using the default (1440, medium) settings and have over 200,000 images. And yes, deleting the previews file and starting over is the only way to fix it, which feels pretty clunky. I just wish we could place a limit on this previews file, or have it automatically discard old previews as we can with 1:1 previews.

I like your idea though - I'll do some new testing with the "Low" quality previews setting this week and see if that's acceptable.
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Rob Cole

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Well, if your previews are set at 1440, and deleting 1:1 previews doesn't buy much, then it's more likely because there just weren't many 1:1 previews to delete, rather than they weren't being deleted (which usually only happens if previews are set higher).

Anyway, +1 vote for being able to discard standard previews as well. I have enough space, but it still bothers me that I can't forcibly rebuild standard previews after changing standard preview settings.

Cheers,
~R.
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Scott Martin

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Good point Rob - we should have "Discard Standard Previews" as the second item in Library>Previews so we can discard them from within the application.
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brandie sunley

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I've been trying to hard to find this solution. Realized that my LR previews were eating nearly 100G on my 500G HDD... RIdiculous.. Its to the point that the Drive was nearly full.. IN less than a year's worth of imports.
ANd Like Scott, I have imports set to medium size upon import and deleting 1:1 previews after 30 days.
Thank you so much for confirming what I was unsure of doing to handle this issue.