diff --git a/lib/bot_bench.py b/lib/bot_bench.py
index 60f3391..d6ea755 100755
--- a/lib/bot_bench.py
+++ b/lib/bot_bench.py
@@ -32,8 +32,9 @@ def setSpotFilter(filter):
 def openShutter(exposure):
    sanityCheck()
    print "Open shutter for %s seconds" % exposure
+   print "Actual open time to tell the shutter is %d mili seconds" % int(1000*exposure*(1.-5/800.))
    a=time.time()
-   bb.ProjectorShutter().exposure(Duration.ofMillis(int(1000*exposure)))
+   bb.ProjectorShutter().exposure(Duration.ofMillis(int(1000*exposure*(1.-5/800.))))
    b=time.time()
    time.sleep(0.03*exposure)
    c=time.time()
diff --git a/lib/pd.py b/lib/pd.py
index 608e10a..3145769 100755
--- a/lib/pd.py
+++ b/lib/pd.py
@@ -56,7 +56,7 @@ def __init__(self, exposure, max_reads=2048):
             Maximum number of reads of monitoring photodiode.  Default: 2048.
         """
 
-        buffertime = exptime*5./800.+2
+        buffertime = 3.0
 
 
         # for exposures over 0.5 sec, nominal PD readout at 60Hz,