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Question about size of Smart Previews... vary according to machine?

Jul 11, 2008
Lightroom Version
Operating System
macOS 10.14 Mojave
I have two Macs, a 13" MBP and a 27" iMac. My LRCC library holds 75,000 photos and uses 560GB on the Adobe cloud.

The MBP is set to keep smart previews locally and the size of the LRCC library in ~/Pictures is 38GB.

The iMac is only 256GB internal drive and so far I have not kept smart previews locally. If I check store smart previews locally on the iMac it says it needs 80GB or so....more than is available. (can't remember the exact number).

Is this simply because smart previews on a 13" machine are smaller than smart previews on a 27" machine?

Incidentally my iPhone and my wife's iPad use 110 GB to store smart previews for all the 75,000, which is a bit surprising compared to the 38GB LRCC library on the MBP.

Last edited:
Feb 1, 2010
West Sussex, UK
Lightroom Experience
Lightroom Version
Classic 8
There's no difference in size of the Smart Previews on different systems, they're a fixed resolution and thus the SP of image A will be the same on whatever system you're using it on.

38GB sounds very low, but you don't say what other settings you are using on the Preferences>Local Storage tab, in particular the percentage value you have set for the photo cache size. There's a minimum library size that must be available, but beyond that you have some control over how much space is additionally used for the cache. That 80GB figure should come down as the percentage value is reduced.

The figures on the iPhone and iPad sound about right, I work on the basis that a smart preview would be around 1.5MB.
Jul 11, 2008
Thanks very much. I think the mystery has just been solved as Finder on the MBP has just caught up and is now showing the LRCC library as 87GB, consistent with the iMac.

It is a pity Adobe don't let us have the LRCC library anywhere except ~/Pictures.