Film reviews are written by journalists, film critics, or other industry persons and are published in various sources including newspapers, magazines and online. These are usually published when the film is released so be sure to have the release date when searching. Because they are produced at the time the film is made, they are considered primary sources. They should be evaluated within the context of the film's creation, reception during a particular historical moment.
Film criticism is an analysis and evaluation of a film and the medium written by academics and film scholars who are influenced by film theory, cultural theory and history and is usually published in scholarly journals. Film criticism can be written at any time, often years after a film is released. Film criticism is considered a secondary source and has the benefit of hindsight: years of historical contextualization and consideration of a filmmaker's body of work. Keep in mind that scholars will often look at film within a theoretical framework - they may consider a film through a feminist lens, a Marxist lens, a queer theory lens. It's not necessary for you to know about these lenses, but identifying a perspective from which you want to consider themes and artistic decisions can help you narrow and develop your topic.
Since film criticism is considered scholarship, use that page at left to search for it.