Today’s Question: Every once in a while, when going to work on an image or export it I get message (to paraphrase) that the original is not found, and do I want to locate or work with smart preview. My question is, if I delete all smart previews will these images that can’t be located be lost to me without smart previews?
Tim’s Quick Answer: If the source image can be located, then deleting the smart preview is safe. If there is a chance the original file has been lost, then the smart preview should be protected as though it was the original.
More Detail: A smart preview in Lightroom Classic is a relatively high-resolution rendering of the source image. Smart previews can be used in place of the source image file within Lightroom Classic. For example, if you have built a smart preview for an image, you can still work with that image (via the smart preview) in the Develop module even if the source file is not currently available. You can even export or share copies of the photo based on the smart preview.
The answer to today’s question depends on the reason the source file is missing. If the smart preview is being used simply as a convenience, such as so you can continue working even when an external hard drive containing the photos isn’t connected, then the smart previews can be thought of as disposable.
However, if the source files can’t be found, then the smart previews suddenly become an important alternative to the originals. If the source files had been accidentally deleted, the smart previews can still be used, and therefore should not be discarded. The smart previews will generally have a lower resolution (at about 2500 pixels on the long side) compared to the original, but reduced resolution is better than no pixels at all.
