I have searched the web but have not found an answer. I use expert tanks in a Jobo ATL. I also develop in trays. I like to make up developers from formulas but have not found a method to determine the correct amount of the active developer which should be used for each sheet of film. Many discussions indicate that you MUST have a sufficient amount of the active developer present but I have found no method of how you determine what that amount is. This appears to a real problem when using dilute developers.