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Library module Reducing size of Smart Previews

Joined
Jul 19, 2014
Messages
22
Location
Crickhowell, S Wales
Lightroom Experience
Intermediate
Lightroom Version
Lightroom Version
Classic 9.2.1
Operating System
Windows 10
I have 40,000 image files and currently using LR Classic the catalogue uses 400 Mb, the Preview cache 23 Gb, and the Smart Previews 213 Gb, using Win 10. The image files are stored on external drives (500Gb). I want to transfer my catalogue to a fast USB so I can also use LR on my laptop for presentations away from home. I have a fast 128 Gb USB stick available. That of course is too small to hold the catalogue and the Smart Previews.

I'm guessing that I need to rebuild my smart previews? Currently the settings are Auto (2048px), and high quality. Again, I'm guessing - if I change this to medium quality and, maybe, 1680 px, will this reduce the size of the file sufficiently? Assuming it will, do I simply delete the Smart Preview folder and allow KR to rebuild when I access each folder, or can I do it piecemeal, by taking individual sub folders in the Smart Preview folder, please? Or have I got this totally wrong?
 
Joined
Sep 29, 2007
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22,465
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Southampton, UK
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Power User
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Cloud Service
Smart preview size won't change, they're always 2560px. Do you need to edit them when you're away? You could only keep smart previews for the ones you'll need to use.
 
Joined
Jul 19, 2014
Messages
22
Location
Crickhowell, S Wales
Lightroom Experience
Intermediate
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Yes, I will need to edit them on the laptop.

I'm surprised that the overall size / space occupied will not reduce - looking at the example of sizes given in your FAQ book it seems that my overall size is too large?
 
Joined
Sep 29, 2007
Messages
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Location
Southampton, UK
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Cloud Service
Hmmm, yes, you're right, it does sound too big for 40k photos. They usually average around 1MB each, although it's dependent on the image content (high ISO / noisier don't compress as well). I wonder if you've got some orphaned previews in there. Yes, you could delete the smart preview folder and then just rebuild them using the Library menu > Previews > Build Smart Previews command when you go to bed.
 
Joined
Jul 19, 2014
Messages
22
Location
Crickhowell, S Wales
Lightroom Experience
Intermediate
Lightroom Version
Thanks, Victoria, I'll do that. Just one more question, please - is it possible to delete onlu=y part of the Smart Preview folder - ie to do it a bit at a time? Then I can prioritise which ones I'm fixing.
 
Joined
Jul 19, 2014
Messages
22
Location
Crickhowell, S Wales
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I don't have any HDR images, but thanks for the suggestion. My difficulty was in identifying specific previews in the folder - ie if I want to delete the previews of one part of my collection, how do I find the relevant previews?
 

Gnits

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Joined
Mar 21, 2015
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Dublin, Ireland.
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Personally, if I was in that situation, I would delete all the Smart previews and just rebuild the folders you are currently working on. In that way you clear all orphaned files for sure and you can monitor how the size of the smart preview folder grows over time.

Every year or two I delete all previews and then run an overnight batch job to rebuild what I think is most relevant to me.
 
Joined
Feb 1, 2010
Messages
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Location
West Sussex, UK
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Advanced
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I don't have any HDR images, but thanks for the suggestion. My difficulty was in identifying specific previews in the folder - ie if I want to delete the previews of one part of my collection, how do I find the relevant previews?
You can select the photos whose smart previews you want to delete, then go to the Library menu and select Previews>Discard Smart Previews. But that's probably not an instant delete, more a background thing.....and I would agree with Gnits, delete the whole Smart Previews cache and rebuild gradually.
 
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