diff -urN rt_v16/rt.py rt_v17/rt.py
--- rt_v16/rt.py	2018-04-03 09:46:11.000000000 +0900
+++ rt_v17/rt.py	2018-04-04 21:33:33.000000000 +0900
@@ -36,6 +36,8 @@
 	col = np.sum(cols, axis=0) if cols else def_col
 	return ut.map_lst( lambda v: min(v, 255), col )
 
+ref_rate = ut.arg_f('ref_rate', 0.001)
+
 def get_col(data, lights, l_g, video, nest_rate=1.0, ref_len=None):
 	if nest_rate < 0.01:
 		return []
@@ -46,7 +48,6 @@
 		return []
 
 	if ref_len:
-		ref_rate = 0.000001
 		lst = ut.filter_lst( lambda crs: crs.get('t') > ref_len * ref_rate, lst )
 		if not lst:
 			return []