diff --git a/.gitignore b/.gitignore
index a38d34b..735edcb 100644
--- a/.gitignore
+++ b/.gitignore
@@ -2,3 +2,4 @@
 /.idea
 /release
 mandelplot
+mandelbrot.png
\ No newline at end of file
diff --git a/README.md b/README.md
index 8cd590b..5de017c 100644
--- a/README.md
+++ b/README.md
@@ -18,6 +18,7 @@ OPTIONS:
 
 - `-V, --version` => Print version information
 
+- `-z --m_set_dimensions <m_set_dimensions>` => Set real and imaginary constraints (real_start,imaginary_startxreal_end,imaginary_end) [default: -2.5,-2.0x1.5,2.0]
 
 ## Naive benchmarks
 Singe-threaded (19200x10800) (pre v0.2.0)