diff --git a/README.md b/README.md
index 0b3021b..17516b7 100755
--- a/README.md
+++ b/README.md
@@ -3,3 +3,9 @@
 Ray tracing rendering experiments
 
 https://raytracing.github.io/
+
+Produced PPM images can be converted to PNG with `imagemagick`:
+
+```
+convert image.ppm image.png
+```