diff --git a/dwt/evidence/real-unit-1280-50pct.png b/dwt/evidence/real-unit-1280-50pct.png
new file mode 100644
index 0000000..c997b28
Binary files /dev/null and b/dwt/evidence/real-unit-1280-50pct.png differ
diff --git a/dwt/notes/REAL_UNIT.md b/dwt/notes/REAL_UNIT.md
index 8140970..6863a7a 100644
--- a/dwt/notes/REAL_UNIT.md
+++ b/dwt/notes/REAL_UNIT.md
@@ -155,3 +155,11 @@ python3 dwt/screenshot.py --host 100.103.100.103 --real --out screen.png
 the Icon Box resize buttons and the `Ethernet Port Error - 24` box.
 
 The emulator geometry is unchanged: 1024x1024 with a 128-byte stride.
+
+### Background references
+
+Both backgrounds are captured at the correct geometry:
+`dwt/evidence/real-unit-1280-1to1.png` (100% white root) and
+`dwt/evidence/real-unit-1280-50pct.png` (50% `1010` root, the owner's
+preference). Only the root's image bytes change; the 256-byte stride and the
+1280x1024 size are identical.