diff --git a/grab.py b/grab.py
index bb54768..f678aaf 100644
--- a/grab.py
+++ b/grab.py
@@ -6,8 +6,11 @@ import os
 import sys
 import time
 
+import imageio
+
 from vncdotool import api
 from twisted.internet import reactor
+
 import paho.mqtt.client as paho
 
 # LOGGING
@@ -68,6 +71,16 @@ NAME=DEVICE_NAME or SANITIZED_HOST
 DEVICE_ID = DEVICE_ID or SANITIZED_HOST
 OBJECT_ID = base64.b32encode(hashlib.sha1(NAME.encode('utf-8')).digest()).decode('utf-8')
 
+def blackwhite(imgf):
+    r = imageio.read(imgf)
+    screen = r.get_data(0).flatten()
+    byt = screen.tobytes()
+    count = len(byt)
+
+    blackcount = byt.count(b'\x00')
+    whitecount = byt.count(b'\xff')
+    return blackcount,whitecount,count
+
 mqtt = paho.Client()
 mqtt.username_pw_set(MQTT_USER, MQTT_PASSWORD)
 mqtt.connect(MQTT_HOST)
@@ -85,8 +98,11 @@ mqtt.publish(f"homeassistant/camera/{DEVICE_ID}/config", json.dumps({
   },
 }), retain=True)
 
+t = None
+
 while True:
-    t = time.time()
+    if t is None:
+        t = time.time()
     with api.connect(VNC_HOST, VNC_PASSWORD) as vnc:
         logger.debug("refreshing for capture")
         vnc.refreshScreen()
@@ -95,6 +111,13 @@ while True:
         logger.debug("publishing to mqtt")
         with open('capture.png', 'rb') as f:
             capture = f.read()
+        (black,white,total) = blackwhite('capture.png')
+        if black > (total / 2): # if it's more than half black, it's a failure
+            logger.warning(f"screen is more than half black.  considering as failure.")
+            continue
+        if white > (total / 2): # if it's more than half white, it's a failure
+            logger.warning(f"screen is more than half white.  considering as failure.")
+            continue
         with open('capture.time', 'wb') as f:
             pass  # touch :D
 
@@ -104,7 +127,8 @@ while True:
         logger.debug(f"sleeping for {time_left}s")
         time.sleep(time_left)
     else:
-        logger.warning(f"interval missed ({time_left}s overdue)")
+        logger.warning(f"interval missed ({0-time_left}s overdue)")
+    t = None
 
 mqtt.loop_end()
 reactor.stop()
diff --git a/health.sh b/health.sh
index c2aadfb..8e43a77 100755
--- a/health.sh
+++ b/health.sh
@@ -3,7 +3,7 @@
 DT=$(date +%s)
 CT=$(stat -c %Z capture.time)
 
-if [ $(( DT - CT )) -gt $INTERVAL ];then
+if [ $(( DT - CT )) -gt $(( 5 * INTERVAL )) ];then
     echo bad
     false
 else
diff --git a/requirements.txt b/requirements.txt
index 17d7728..158cb68 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -3,6 +3,7 @@ Automat==22.10.0
 constantly==15.1.0
 hyperlink==21.0.0
 idna==3.4
+imageio==2.31.1
 incremental==22.10.0
 paho-mqtt==1.6.1
 Pillow==10.0.0