diff --git a/cuburn/code/filtering.py b/cuburn/code/filtering.py
index b191c33..7faa2d1 100644
--- a/cuburn/code/filtering.py
+++ b/cuburn/code/filtering.py
@@ -137,7 +137,7 @@ void logscale(float4 *pixbuf, float4 *outbuf, float k1, float k2) {
 
 // See helpers/filt_err.py for source of these values.
 #define MIN_SD 0.23299530f
-#define MAX_SD 4.33333333f
+#define MAX_SD 2.5f
 
 __global__
 void density_est(float4 *pixbuf, float4 *outbuf,