This film can be caused by two things. One is soap residue and the other is mineral residue.
A simple test can be done to determine what type of film you have. Take a glass with film on it and run it under the faucet with water and use your thumb to rub the film. Dry the glass completely and check if the film is still there.
Soap film will wash off easily and if the glass is clean then the film is soap suds. The problem from too much soap can be caused by multiple things. A poor drain, not enough water, too much rinse agent or the water is not hot enough. These are things that can be checked and repaired.
This can be solved easily with white vinegar. Load your dishwasher up with the dishes that have a film on them and start a rinse only cycle. After the unit fills and starts to wash, pause the unit and open the door. Add a cup of white vinegar and finish the rinse cycle. This will clean off any mineral deposits and the glasses will be clean with no film.