diff --git a/CHANGELOG.md b/CHANGELOG.md
index 110ae498..880f5e68 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -14,6 +14,10 @@ All dates in this file are given in the [UTC time zone](https://en.wikipedia.org
 - (Hardware controller) The bitrate of the camera preview stream has been reduced slightly from ~8 Mbps to ~7 Mbps.
 - (Hardware controller) The framerate of the camera preview stream is now explicitly limited to 25 fps.
 
+### Fixed
+
+- (Breaking change; segmenter) The previously incorrect method for filtering segmented objects by size has now been corrected to filter object sizes by filled area rather than bounding box area, and directly using the mesh size as the threshold for equivalent spherical diameter (ESD) instead of calculating a fictional ESD.
+
 ## v2024.0.0-beta.2 - 2024-08-19
 
 ### Changed
diff --git a/processing/segmenter/planktoscope/segmenter/__init__.py b/processing/segmenter/planktoscope/segmenter/__init__.py
index fb38a8cb..aca1dc5e 100644
--- a/processing/segmenter/planktoscope/segmenter/__init__.py
+++ b/processing/segmenter/planktoscope/segmenter/__init__.py
@@ -474,17 +474,16 @@ def __augment_slice(dim_slice, max_dims, size=10):
             dim_slice = tuple(dim_slice)
             return dim_slice
 
-        minMesh = self.__global_metadata.get("acq_minimum_mesh", 20)  # microns
-        minESD = minMesh * 2
-        minArea = math.pi * (minESD / 2) * (minESD / 2)
-        pixel_size = self.__global_metadata.get("process_pixel", 1.0)
-        # minsizepix = minArea / pixel_size / pixel_size
-        minsizepix = (minESD / pixel_size) ** 2
+        min_mesh = self.__global_metadata.get("acq_minimum_mesh", 20)  # microns
+        min_esd = min_mesh # or process_min_ESD in the future (microns)
+        pixel_size = self.__global_metadata["process_pixel"]
+        min_radius = min_esd / 2 / pixel_size # (pixels)
+        min_area = math.pi * min_radius * min_radius
 
         labels, nlabels = skimage.measure.label(mask, return_num=True)
         regionprops = skimage.measure.regionprops(labels)
         regionprops_filtered = [
-            region for region in regionprops if region.bbox_area >= minsizepix
+            region for region in regionprops if region.filled_area >= min_area
         ]
         object_number = len(regionprops_filtered)
         logger.debug(f"Found {nlabels} labels, or {object_number} after size filtering")