diff --git a/README.md b/README.md
index 3632aa8..a915a4e 100644
--- a/README.md
+++ b/README.md
@@ -226,7 +226,7 @@ dark areas as light.
 exposed through a negative, which can be achieved either by placing the negative and paper
 in close proximity or by projecting a negative image onto the paper.
 
-• s = (L-1) – r , where L= number of gray levels
+• s = (L-1) – r, where L= number of gray levels