diff --git a/crates/engine/src/lens_profiles.rs b/crates/engine/src/lens_profiles.rs
index afcb0ab399..c52d49f392 100644
--- a/crates/engine/src/lens_profiles.rs
+++ b/crates/engine/src/lens_profiles.rs
@@ -90,7 +90,7 @@ pub fn database() -> Option<Arc<LensDb>> {
     }
     let generation = generation();
     // the app's own folder without its marker is a download that never finished: not read (the start fetches it)
-    let db = if downloaded && !crate::lensfun_download::complete(&dir) { None } else { load(&dir) };
+    let db = if downloaded && !crate::lensfun_download::complete(&dir) { None } else { load(&dir, downloaded) };
     let mut loaded = LOADED.write().unwrap_or_else(PoisonError::into_inner);
     // a reload while the files were read: they may be the old ones, so they aren't kept (the next call reads again)
     if GENERATION.load(Ordering::Relaxed) == generation {
@@ -99,8 +99,10 @@ pub fn database() -> Option<Arc<LensDb>> {
     db
 }
 
-fn load(dir: &Path) -> Option<Arc<LensDb>> {
+fn load(dir: &Path, downloaded: bool) -> Option<Arc<LensDb>> {
+    let whose = if downloaded { "downloaded" } else { ENV };
     if !dir.is_dir() {
+        log::warn!("lens database: {} ({whose}) is missing or not a folder", dir.display());
         return None;
     }
     match LensDb::load_dir(dir) {
@@ -108,6 +110,8 @@ fn load(dir: &Path) -> Option<Arc<LensDb>> {
             for (file, e) in errors {
                 log::warn!("lens database: skipped {file}: {e}");
             }
+            let (level, line) = summary(dir, whose, &db);
+            log::log!(level, "{line}");
             (!db.lenses.is_empty()).then(|| Arc::new(db))
         }
         Err(e) => {
@@ -117,6 +121,17 @@ fn load(dir: &Path) -> Option<Arc<LensDb>> {
     }
 }
 
+/// The log line for a database read from `dir`: where it is and how many lenses and cameras it has, so a user
+/// setting up `LIGHTCRAFT_LENSFUN_DIR` can see whether it was found; a folder without lenses is a warning.
+fn summary(dir: &Path, whose: &str, db: &LensDb) -> (log::Level, String) {
+    let (lenses, cameras) = (db.lenses.len(), db.cameras.len());
+    if lenses == 0 {
+        (log::Level::Warn, format!("lens database: no lenses in {} ({whose}); lens profiles are not applied", dir.display()))
+    } else {
+        (log::Level::Info, format!("lens database: read {} ({whose}): lenses {lenses}, cameras {cameras}", dir.display()))
+    }
+}
+
 /// The database's name for the lens a photo's file calls `lens` (taken with `camera`, the make and model as the
 /// library shows them): "Canon EF 70-200mm f/2.8L IS II USM". `None` without a database or a match.
 pub fn profile_name(db: &LensDb, camera: &str, lens: &str) -> Option<String> {
@@ -193,6 +208,18 @@ mod tests {
         }
     }
 
+    /// The log says where the database was read from and what it holds, and warns when it holds no lenses (#2511).
+    #[test]
+    fn the_log_names_the_folder_and_what_it_holds() {
+        let dir = Path::new("/lensfun/db");
+        let (level, line) = summary(dir, ENV, &LensDb::parse(DB).unwrap());
+        assert_eq!(level, log::Level::Info);
+        assert!(line.contains("lenses 1, cameras 1") && line.contains("/lensfun/db") && line.contains(ENV), "{line}");
+        let (level, line) = summary(dir, "downloaded", &LensDb::parse("<lensdatabase></lensdatabase>").unwrap());
+        assert_eq!(level, log::Level::Warn);
+        assert!(line.contains("no lenses") && line.contains("downloaded"), "{line}");
+    }
+
     #[test]
     fn exif_lens_is_found_and_converted() {
         let db = LensDb::parse(DB).unwrap();
diff --git a/docs/lens-profiles.md b/docs/lens-profiles.md
index c49ee6ad42..e55b38ff4c 100644
--- a/docs/lens-profiles.md
+++ b/docs/lens-profiles.md
@@ -50,6 +50,8 @@ Sync carry Enable Lens Corrections and its amounts, and each photo keeps the pro
 (`crates/engine/src/tests/lens_refresh.rs`).
 
 Files are read once per folder and again after a download. Invalid files are skipped with a warning in the log.
+Each read logs the folder, whether it is the download or `LIGHTCRAFT_LENSFUN_DIR`, and how many lenses and cameras
+it holds; a folder that is missing or holds no lenses is logged as a warning (#2511).
 
 ## What is applied