Today’s Question: I have a follow-up question to your October 28 email about deleting previews. With regard to deleting previews in Lightroom Classic, wouldn’t it also be possible to delete previews from within Lightroom? I see that I can delete Previews by going to the menu and choosing Library > Previews > Discard 1:1 Previews. And, I can do this on a folder basis. This seems like a good option after I have finished processing photos within a folder that I will not likely need to revisit again.
Tim’s Quick Answer: The 1:1 previews in Lightroom Classic are a subset of the overall previews referenced in my answer about deleting the previews file. By default 1:1 previews are discarded automatically after 30 days, but you could also discard them manually (or change the frequency). But this would generally not free up as much space as deleting the full previews file.
More Detail: I generally recommend generating Standard previews when you import your photos into Lightroom Classic. In addition, you can generate 1:1 (or full-resolution) previews if you prefer. The 1:1 previews will also be generated automatically anytime you zoom in on an image in the Library module.
The Standard previews are not full resolution, and therefore the 1:1 previews will be larger than Standard previews. Thus, it can be helpful to discard 1:1 previews if you won’t likely need them in the future. For example, after reviewing and optimizing photos from a given photo trip, you likely would not need the 1:1 previews for those images. And, of course, if you zoom in on one of those images, the 1:1 preview will be generated again automatically.
You can adjust the settings for automatically discarding 1:1 previews in the Catalog Settings dialog. On the File Handling tab you’ll find the “Automatically Discard 1:1 Previews” popup. From that popup you can choose to have 1:1 previews discarded if they have not been used in thirty days, one week, or one day. There is also an option to never discard 1:1 previews if you prefer.
I recommend selecting an option for automatically discarding the 1:1 previews based on how frequently you tend to go back to your images. If you need to free up hard drive space, you could also discard previews manually for some (or all) of your photos by selecting those photos and choosing Library > Previews > Discard 1:1 Previews from the menu.