I have images of film formed on the bottom of a 50mL beaker, and I have been trying to figure out the surface area. I could easily use features on imageJ to do that, but I want to know which area is covered by the film and which is not covered. I have explored the threshold feature, and I think either I am not doing it correctly or I am not very certain what I am doing is right. Is there anything I can do or process to follow to accurately know the covered area and determine the surface area based on that? I have attached images of the empty beaker and the beaker with the film. Thank you.