Today’s Question: I have generated 1:1 previews for my photos in Lightroom, but I often still see the “loading” message when I select an image. Shouldn’t the 1:1 previews make the previews load instantly?
Tim’s Quick Answer: Just because you have loaded 1:1 previews for your photos does not mean those previews will load instantly. There are a variety of factors that can impact the speed at which previews (of any resolution) can be loaded.
More Detail: The 1:1 preview option in Lightroom enables you to have a full-resolution preview for your images in the Library module. These previews will be generated automatically whenever you zoom in on an image for which there isn’t already a 1:1 preview. If you have already generated 1:1 previews for your photos, those previews can be loaded from the previews file more quickly than a new preview can be generated.
In addition, however, there are some other issues that can impact the overall speed at which previews can be loaded.
In the context of 1:1 previews, it is important to keep in mind that by default Lightroom will discard the 1:1 previews for your images if they have not been accessed in the last thirty days. As a result, it is possible you are actually experiencing slower performance for some images because the previews have been discarded and therefore need to be re-built. If this is the issue, keeping the 1:1 previews for a longer duration can help. You can select Edit > Catalog Settings on Windows or Lightroom > Catalog Settings on Macintosh to bring up the Catalog Settings dialog. On the File Handling tab you can choose when the 1:1 previews should be discarded, including an option for “Never”.
Next, I would make sure that your Lightroom catalog (and therefore all of the preview files) are located on the fastest hard drive available. In general that means storing the catalog on an internal hard drive on your computer, but the point is that overall hard drive performance affects how quickly previews can load.
You can also improve overall performance in Lightroom by optimizing the catalog periodically. This is an option available when backing up your catalog. If you’re not using the built-in feature in Lightroom to backup your catalog (and therefore not using the catalog optimization feature available as part of the backup) I recommend “manually” optimizing periodically by choosing File > Optimize Catalog from the menu.
Finally, in some cases you may actually find it helpful to discard the previews altogether and have Lightroom generate them again for you. I have had a couple of occasions where overall performance loading images in Lightroom got to be quite slow, and discarding all previews provided a significant benefit.
To do so, you will first want to make sure that Lightroom is closed. Then go to the folder that contains your catalog and delete the file that has the same name as your actual catalog (lrcat) file, but with the word “Previews” appended to the filename and with a filename extension of “lrdata”.
When you then launch Lightroom again, you can re-generate previews for all photos. To do so you can go to the All Photographs collection in the Catalog section of the left panel of the Library module and then choose Edit > Select All from the menu. Then go to the Library menu on the menu bar and choose Previews > Build 1:1 Previews (or “Build Standard-Sized Previews” if you don’t need the full-resolution previews). This will cause Lightroom to build previews for all images, which can take considerable time but can then help ensure improved browsing performance.