3D Edge and Symmetry filter parameters


I am using the 3D Edge and Symmetry filter plugin from the 3D ImageJ Suite update site to process some emulsion micrographs (100X) and then analysing the oil droplets for a size: 0-infinity and circularity : 0.5 to 1.00.

For the 3D Edge and Symmetry filter plugin, I am giving a value of 0.8 for the smoothing alpha parameter and for the radius, I have tried values from 4 to 30. Each time I increase the radius, the count of droplets detected is getting reduced and the average area of the droplets is getting increased.

Could anyone advise if the algorithm is missing smaller droplets when I increase the radius value.?


Hi suvgit,

The number of droplets found depends also on the method you are using to detect them. The symmetry filter is quite sensitive to the radius of the object, you should use a value for the radius parameter that is slightly larger then the radius of the particles you want to detect. If you want to detect aprticles with different sizes you may consider having two detections, one for small particles and one for big particles.

Hope this helps,



Thank you Thomas for your reply.
Since I am analysing not only perfect circles (0.5 to 1.00), how would the radial symmetry work ?
If I am giving the radius as 6 pixels and if my scale is 4 pixels/um, then would the algorithm consider only circular droplets with <= 6 pixels radius ?


Hi Suvgit,

My understanding of the algorithm is that it will best detect round particles, however you can use it with ellipsoid-shape particles. Maybe you can see this algorithm like detecting the “skeleton” or the “core” of your particles based on their edges.
Here a simple example made with my “3D Draw Shape” plugin, the ellispoid has radii of 20,10,10 and I tried with incresaing radii for symmetry filter of 10,20, 30 .

as you can see the best detection is when the radius is 20.
Hope this helps

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Thank you very much Thomas!!
Best Regards