THE CORCORAN Gallery of Art's exhibit on Niagara Falls -- "Niagara: Two Centuries of Changing Attitudes, 1697- 1901" -- features a 30-minute film on the subject. A Florentine Films production by Diane Garey and Lawrence Hott, Niagara Falls won a first place award at this year's American Film Festival. The film will be screened Tuesdays through Fridays from 11 to 11:30 in the morning and Saturdays and Sundays from 2 to 2:30 (except October 26) throughout the run of the exhibit, which concludes November 24.

The film will be shown in the Frances and Armand Hammer Auditorium at the gallery, which is a block west of the White House, at 17th Street and New York Avenue NW. While admission to the gallery is free, you must be a Corcoran member to get into the exhibit at no charge. Cost for the exhibit is $1.50 for adults and 50 cents for students and senior citizens. Call 638-3211 for further information.

The National Archives' "War Film" program continues Friday at noon with a free showing of Divide and Conquer, the third installment of Frank Capra's "Why We Fight" series. Featuring animation by the Walt Disney studios and music by Max Steiner and Dimitri Tiomkin, the 42-minute film explains why the U.S. entered World War II, focusing on Hitler's invasion of Western Europe and France's surrender. The screening, in the Archives auditorium, is free. The Archives is at Pennsylvania Avenue and Eighth Street NW. Call 523-3000.

Oscar-winning director Paul Wagner (The Stone Carvers) will lecture on independent filmmaking Friday at 7:30 p.m. in the American University's Weschler Theater. Clips from the film will be shown. Wagner will answer questions after the lecture. Admission is free. Call 885-2042.

The Biograph's Soviet film series continues with the Washington premiere of Pyotr Todorovsky's Wartime Romance, Friday through Monday. A nominee for Best Foreign Film last year, the movie follows a young man's obsession with the girlfriend of his commanding officer during World War II. Tuesday through Thursday, Grigori Kozintzev's 1957 adaptation of Don Quixote will share a bill with Sergei Parajanov's impressionistic 1964 love story, Shadows of Forgotten Ancestors. Call 333-2696 for information and a schedule.

Daniel Schmid's Tosca's Kiss will have its second and final screening Friday night at 8 in the Hirshhorn Museum auditorium. Saturday at 2, there'll be an encore screening of David Sylvester's Francis Bacon and the Brutality of Fact, an hour-long documentary on the artist.

Thursday and October 18 at 8, the museum will host the Washington premiere of Sans Soleil ("Sunless"), the 1982 film by -- and about -- French director Chris Marker, who made the groundbreaking short film La Jet,ee more than 20 years ago. A return to the impressionistic travelogue format of his early films, "Sunless" has been called a summation of all Marker's early work. All Hirshhorn programs are free; call 357-2700.

The collection of New Zealand films at The American Film Institute Theater yields at least one diamond in the rough this weekend: Sleeping Dogs, Roger Donaldson's political thriller from 1977. The film (which features broad performances by a young Sam Neill and an old but vigorous Warren Oates) is generally considered to be the movie that got the ball rolling for the rapidly expanding New Zealand film industry. The movie is showing but once, Saturday at 4, in the AFI Theater at the Kennedy Center. Call 785-4601.

Hollywood producer and screenplay consultant Michael Hauge will lead a two-day screenwriting course, "How to Write and Sell Your Screenplay," Saturday and Sunday from 10 to 5 at the University of Maryland. The program will offer sessions on story selection, character development, structure and the business end of screenwriting. The course fee is $145, including all instruction and materials. Registration is Friday until 7:30 p.m. and again Saturday beginning at 9. Call 301/985-7157 or 1/800/638-3902 (toll-free within the 301 area) for more details.

The series of dance films at the Martin Luther King Memorial Library continues Tuesday at 7 with a program of three short films: Moor's Pavane (with Jose Limon as Othello; Coast Zone (directed by Charles Atlas and featuring choreography by Merce Cunningham); and In a Rehearsal Room (a brief documentary of a pre-performance warmup with Cynthia Gregory and Ivan Nagy). The program is free, and will be held in Room A-5 of the library, 901 G Street NW. Call 727-1271.

The Third Annual Washington Super-8 Showcase will be held October 18-19 at American University's Weschler Theater. The festival is now soliciting super-8 films for screening. Last year's bash featured 36 films by 21 filmmakers (some of whom came from as far away as New York City). To enter, call Ray Schmitt (day 287-7317, evening 868-3461) or Chris Todd (day 287-8091, evening 836- 5269). The deadline for entries is Tuesday. There is no charge for submission.

Douglas Trumbull has two new films coming out on his patented Showscan process, A Tour of the Universe and Let's Go. On Wednesday, the Washington Film Council invites the public to a general membership meeting at the Showbiz Pizza Place, 9404 Main Street in Fairfax, to see these films, eat pizza and talk film. This restaurant, wilth its specially built theater, is so far the only easily accessible outlet for Trumbull's new process, which uses high-speed photography and projection in addition to high-fidelity sound. Cost is $12.50 for Film Council members and $16 for nonmembers (including the eats). To learn more, call Paul Klein at 576-2106.

George Mason University is the site for an International Film Festival that will feature films from Brazil, Mexico and Colombia. The next attraction is Pixote, the film that launched Hector Babenco's career. It will be shown Thursday at 7:30 at the university Lecture Hall. The screenings are free and open to the public. For more information and the schedule, call 703/323-2000. George Mason University is at 4400 University Drive in Fairfax County.