Smart Previews are much smaller than the original photos. You can free up disk space on devices with smaller storage capacities (for example, SSD drives) by choosing to keep original files on a high-capacity external device (for example, NAS devices or external discs). For example, 500 raw images from a high-end DSLR camera may occupy 14 GB of disk space. The Smart Preview files for the same images amounted to 400 MB of disk space.