diff --git a/src/filters/colormatrix/ColorMatrixFilter.js b/src/filters/colormatrix/ColorMatrixFilter.js
index e6fde6e..e1d647a 100644
--- a/src/filters/colormatrix/ColorMatrixFilter.js
+++ b/src/filters/colormatrix/ColorMatrixFilter.js
@@ -244,7 +244,7 @@
     contrast(amount, multiply)
     {
         const v = (amount || 0) + 1;
-        const o = -128 * (v - 1);
+        const o = -0.5 * (v - 1);
 
         const matrix = [
             v, 0, 0, 0, o,