Right next to the threshold functions is a vi that will determine the threshold level. You can select from several different algorithms, depending on which one works best for your application. There is also a vi for determining multiple threshold levels. I have used that before when the blobs where varying intensities.
If these functions don't do the job for you, you should probably post an example image so we can look at it and suggest ideas of how to threshold it.
Bruce
Bruce Ammons
Ammons Engineering
