I am new to ImageJ, but would like to perform a contact angle measurement of droplets on several surfaces. I found that ImageJ with the plugin drop_analysis can do this with either the so-called LB-ADSA or the DropSnake method. As my samples are not completely leveled, I think the DropSnake method will work best. I have downloaded both ImageJ and the plugin from this page: http://bigwww.epfl.ch/demo/dropanalysis/#soft and I am following this manual: http://mmrc.caltech.edu/Gniometeer/drop_analysis/drop_analysis.pdf I try to follow the steps in this manual but do not success completely. When I follow the steps as in “Typical Utilization” for DropSnake, as described on page 2, I am unable to attain the optimal red line/dots around the droplet (as they do in this video: https://vimeo.com/12449610). It is like the buttons are unable to be pressed down. Does anyone know they reason for this? I would really appreciate any help!!