Colony counting of E. coli on Agarplates



i have the following problem:
I tried to use CellProfiler 2.2.0 to count colonies of E. coli on Agarplates. For this i used the following modules: ColorToGray->IdentifyPrimaryObjects->SaveImages. My problem is that no matter what options i use (for example threshhold, diameter of objects…) the cellprofiler counts countless colonies because he recognises the edge of the petri dish as colonies.
Can someone help me im a beginner with Cellprofiler?


You may need to mask out the plate before trying to count the colonies- here is a link to a tutorial for a similar task. It’s for counting yeast colonies rather than E. coli, but the plate masking steps should be the same.