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Preview cache

Forum|Forum|7 years ago
May 24, 2018
4 replies
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Hello,

I am trying to reduce my Preview cache. Please see image below...

I am on "automaticaly discard 1:1 Previews after one day" since 1 week and no change on the preview cache.

How can I reduce the size of my preview cache ?

Thank you !!

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Correct answer Per Berntsen

You could delete the whole preview cache and start over building previews.

Lightroom will then rebuild the previews as you browse the folders in the Library, i.e. a folder you haven't visited will not rebuild previews until you click on it. Alternatively, click on All photographs in the Catalog panel, and Lightroom will create standard previews for all of them, which might take several hours.

To delete the preview cache, with Lightroom closed, go to the folder containing your catalog, then delete the folder (may be listed as a file on a Mac) whose name ends in Previews.lrdata. Do not delete anything else.

It seems that you have a 4k monitor since your standard previews are 3440 pixels, and that will of course lead to a much larger preview cache than with a regular monitor. My monitor is 1920 pixels wide, so my standard previews are only 1440 pixels.

If we had the same number of images, your preview cache would probably be more than twice the size of mine.

Felix13-1710Author

Participant

Thank you so much for your so precious help and very instructive answers !!!!

Ian Lyons

Community Expert

If using a MacBook Pro (late 2016 or 2017) then manually set Standard Preview Size to 2880px instead of Auto. This is the native resolution of the display, although Apple scales to 3440px by default, hence Lr choosing same for Auto. Close Lr then trash the lrdata file. Relaunch Lr and rebuild your previews from scratch. With 2880px your preview cache will be smaller and the previews will build much faster.

Todd Shaner

Legend

https://forums.adobe.com/people/Ian+Lyons wrote
If using a MacBook Pro (late 2016 or 2017) then manually set Standard Preview Size to 2880px instead of Auto.

Just keep in mind the 2880 setting will only work for camera image files with a long edge dimension greater than 5760 pixels (2 x 2880). For a camera with 2:3 aspect ratio that would be an image file greater than 22.1 megapixels (5760x3840). The 'Standard Preview Size' must be less than 50% of the image file's long edge dimension to enable discarding 1:1 Previews and prevent them from being "automatically" rebuilt.

Ian Lyons

Community Expert

trshaner wrote
https://forums.adobe.com/people/Ian+Lyons wrote
If using a MacBook Pro (late 2016 or 2017) then manually set Standard Preview Size to 2880px instead of Auto.
Just keep in mind the 2880 setting will only work for camera image files with a long edge dimension greater than 5760 pixels (2 x 2880).

See Why is the Lightroom preview folder so big, even after purging the 1:1 previews? from 2010

Todd Shaner

Legend

Felix13-1710 wrote
I am on "automaticaly discard 1:1 Previews after one day" since 1 week and no change on the preview cache.

LR will only discard 1:1 Previews if the selected 'Standard Preview Size' is less than 50% of the image file long edge dimension.

http://www.lightroomfanatic.com/tutorials/behind-the-scenes/deleting-11-previews-lightroom-doesnt-reduce-preview-file-si…

For example if shooting with a 24 megapixel camera (4000x6000) 50% of the long edge is 3000 pixels. Your setting of Auto 3440px is greater than 50% or 3000 pixels, which will not allow discarding 1:1 Previews. You can remove the Previews.lrdata folder and start over, but then new 1:1 Previews will be created as you browse in the Library module. Eventually you'll be right back where you started.

Select a 'Standard Preview Size' that is less than 50% of the image file long edge dimension, restart LR and see if you can now discard the 1:1 Previews. If using multiple cameras with different resolution you'll need to set the 'Standard Preview Size' to <50% of the lowest resolution images in your catalog to allow all of them to be discarded. However if you set it too low then the Fit view for your higher resolution image files will appear smaller in the Loupe view window with Fit or Fill. I've never tried this myself so let me know if you have any questions. We'll figure it out.

Per Berntsen

Correct answer

Community Expert

You could delete the whole preview cache and start over building previews.

Lightroom will then rebuild the previews as you browse the folders in the Library, i.e. a folder you haven't visited will not rebuild previews until you click on it. Alternatively, click on All photographs in the Catalog panel, and Lightroom will create standard previews for all of them, which might take several hours.

To delete the preview cache, with Lightroom closed, go to the folder containing your catalog, then delete the folder (may be listed as a file on a Mac) whose name ends in Previews.lrdata. Do not delete anything else.

It seems that you have a 4k monitor since your standard previews are 3440 pixels, and that will of course lead to a much larger preview cache than with a regular monitor. My monitor is 1920 pixels wide, so my standard previews are only 1440 pixels.

If we had the same number of images, your preview cache would probably be more than twice the size of mine.

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