diff --git a/picamera_coverage.zip b/picamera_coverage.zip
index 4a6c1856..09438bb3 100644
Binary files a/picamera_coverage.zip and b/picamera_coverage.zip differ
diff --git a/src/openflexure_microscope_server/things/background_detect.py b/src/openflexure_microscope_server/things/background_detect.py
index 19ab6874..8039605f 100644
--- a/src/openflexure_microscope_server/things/background_detect.py
+++ b/src/openflexure_microscope_server/things/background_detect.py
@@ -99,14 +99,14 @@ class ColourChannelDetectLUV(BackgroundDetectAlgorithm):
     # provided there.
     min_stds = [0.5, 0.3, 0.5]
 
-    channel_tolerance: float = lt.setting(default=7.0)
+    channel_tolerance: float = lt.setting(default=7.0, ge=0)
     """Channel Tolerance
 
     The number of standard deviations a pixel value must be from the background mean
     to be considered sample.
     """
 
-    min_sample_coverage: float = lt.setting(default=25)
+    min_sample_coverage: float = lt.setting(default=25, ge=0, le=100)
     """Sample Coverage Required (%)
 
     The minimum percentage of the image that needs to be identified as sample for the
@@ -223,14 +223,14 @@ class ChannelDeviationLUV(BackgroundDetectAlgorithm):
     # LUV colour space not converting to the CIELUV numbers)
     min_stds = [0.5, 0.3, 0.5]
 
-    channel_tolerance: float = lt.setting(default=7.0)
+    channel_tolerance: float = lt.setting(default=7.0, ge=0)
     """Channel Tolerance
 
     The number of standard deviations a pixel value must be from the background mean
     to be considered sample.
     """
 
-    min_sample_coverage: float = lt.setting(default=25)
+    min_sample_coverage: float = lt.setting(default=25, ge=0, le=100)
     """Sample Coverage Required (%)
 
     The minimum percentage of the image that needs to be identified as sample for the
diff --git a/src/openflexure_microscope_server/things/camera/__init__.py b/src/openflexure_microscope_server/things/camera/__init__.py
index dd4f6cdd..6b9bc323 100644
--- a/src/openflexure_microscope_server/things/camera/__init__.py
+++ b/src/openflexure_microscope_server/things/camera/__init__.py
@@ -274,7 +274,7 @@ class BaseCamera(lt.Thing):
             "CameraThings must define their own capture_array method"
         )
 
-    downsampled_array_factor: int = lt.property(default=2)
+    downsampled_array_factor: int = lt.property(default=2, ge=1)
     """The downsampling factor when calling capture_downsampled_array."""
 
     @lt.action
@@ -565,7 +565,7 @@ class BaseCamera(lt.Thing):
         except Exception as e:
             raise IOError(f"An error occurred while saving {jpeg_path}") from e
 
-    settling_time: float = lt.setting(default=0.2)
+    settling_time: float = lt.setting(default=0.2, ge=0)
     """The settling time when calling the ``settle()`` method."""
 
     @lt.action
diff --git a/src/openflexure_microscope_server/things/camera/simulation.py b/src/openflexure_microscope_server/things/camera/simulation.py
index 31e3979e..d75c36e5 100644
--- a/src/openflexure_microscope_server/things/camera/simulation.py
+++ b/src/openflexure_microscope_server/things/camera/simulation.py
@@ -172,6 +172,8 @@ class SimulatedCamera(BaseCamera):
 
     @blob_density.setter
     def _set_blob_density(self, value: int) -> None:
+        if value < 0:
+            raise ValueError("Sample density must be >= 0")
         self._blob_density = value
         if self._capture_enabled:
             self.generate_canvas()
@@ -457,7 +459,7 @@ class SimulatedCamera(BaseCamera):
             return self._capture_thread.is_alive()
         return False
 
-    noise_level: float = lt.property(default=2.0)
+    noise_level: float = lt.property(default=2.0, ge=0, le=50)
 
     def _capture_frames(self) -> None:
         last_frame_t = time.time()