Deleting Photos to Create Space on Mac

I am trying to create more space on my Mac by deleting photos. I have deleted 1000's of photos and videos (after backing them up). I cleared the "Recently Deleted" folder after deleting each batch of photos. My trash is empty. I have cleared all the cache files from my computer. However, the number of GB devoted to storing photos stays stubbornly at 68GB no matter how many photos I delete. What's going on? Why isn't the storage space increasing as I delete my photos?