diff --git a/README.md b/README.md
index 90bfe83..a75f15b 100644
--- a/README.md
+++ b/README.md
@@ -699,10 +699,11 @@ synchronous getters look at the disk and never touch the network:
 
 - `photo.savePath` → `string | undefined` — where `lib.backup()` writes the
   original, `originals/<fileID>.<ext>` under the `downloadDirectory` the library
-  was opened with, whether or not it is there yet. For a live photo the backup
-  has stored, it is the image's path, whose extension comes from inside the live
-  photo and can differ from the title's. `undefined` when the library has no
-  `downloadDirectory` or no content source.
+  was opened with, whether or not it is there yet: for a live photo already
+  stored, its image. For a live photo not yet stored, it carries the title's
+  extension, and the backup may store the image under a different one, found
+  inside the live photo. `undefined` when the library has no `downloadDirectory`
+  or no content source.
 - `photo.isLocal` → `boolean` — whether the whole original is at `savePath`.
 
 Four async methods may download:
diff --git a/src/library/read.ts b/src/library/read.ts
index e34abeb..a10731d 100644
--- a/src/library/read.ts
+++ b/src/library/read.ts
@@ -89,9 +89,11 @@ export class Photo {
         return this.rec.isHidden;
     }
 
-    // The path `lib.backup()` writes the original to in the library's download
-    // directory, whether or not it is there yet; for a live photo, its image.
-    // Undefined when the library has no download directory or no content
+    // Where `lib.backup()` stores the original in the library's download
+    // directory, whether or not it is there yet: for a live photo already
+    // stored, its image. For a live photo not yet stored, it carries the
+    // title's extension, and the backup may store the image under a different
+    // one. Undefined when the library has no download directory or no content
     // cache.
     get savePath(): string | undefined {
         return this.cache?.savePath(this.rec.fileID);