I'm a beginner with ImageJ, so sorry if this is a basic question. I have many images of cells of which I would like to calculate the average total fluorescence. However, each time I take a measurement of the cell, it sets the max and min pixel values according to that particular image. So an image with clearly higher fluorescence values may have a lower average total fluorescence if only a couple of the cells have the fluorescence, whereas an image with all cells having barely any fluorescence will have a higher average fluorescence value. Could someone please let me know how would I be able to calculate the average fluorescence of the image according to a certain base point?