Question: Which film director, Frank Pierson or Peter Tscherkassky, primarily used a darkroom rather than digital film to produce their works?

Context paragraphs:
In Country: In Country is a 1989 American drama film produced and directed by Norman Jewison, starring Bruce Willis and Emily Lloyd.  The screenplay by Frank Pierson and Cynthia Cidre was based on the novel by Bobbie Ann Mason.  The original music score was composed by James Horner.  Willis earned a best supporting actor Golden Globe nomination for his role.

Darkroom manipulation: Darkroom manipulation is a traditional method of manipulating photographs without the use of computers.  Some of the common techniques for darkroom manipulation are dodging, burning, and masking, which are undoubtedly similar to digital manipulations but everything is done physically rather than virtually.  Darkroom manipulation is also used to remove unwanted areas and changing the background of the image, through many techniques this process can be done.

The Anderson Tapes: The Anderson Tapes is a Technicolor 1971 American crime film in Panavision directed by Sidney Lumet, starring Sean Connery and featuring Dyan Cannon, Martin Balsam, and comedian Alan King.  The screenplay was written by Frank Pierson, based upon a best-selling 1970 novel of the same name by Lawrence Sanders.  The film is scored by Quincy Jones and marks the feature film debut of Christopher Walken.

Peter Tscherkassky: Peter Tscherkassky (born October 3, 1958) is an Austrian avant-garde filmmaker who works primarily with found footage.  All of his work is done with film and heavily edited in the darkroom, rather than relying on recent advances in digital film.

Citizen Cohn: Citizen Cohn is a 1992 cable film covering the life of Joseph McCarthy's controversial chief counsel Roy Cohn.  James Woods, who starred as Cohn, was nominated for both an Emmy and a Golden Globe for his performance.  "Citizen Cohn" also stars Joe Don Baker (as McCarthy), Ed Flanders (as Cohn's courtroom nemesis Joseph Welch), Frederic Forrest (as writer Dashiell Hammett), and Pat Hingle (as Cohn's onetime mentor J. Edgar Hoover).  It was directed by Frank Pierson.  The movie was filmed on location in Pittsburgh, Pennsylvania.

Somebody Has to Shoot the Picture: Somebody Has to Shoot the Picture is a 1990 American made-for-television prison drama film written by photojournalist Doug Magee, inspired by his interviews with and photos of death row prisoners.  The film was directed by Frank Pierson.

Dirty Pictures: Dirty Pictures is a 2000 American docudrama directed by Frank Pierson.  The teleplay by Ilene Chaiken focuses on the 1990 trial of Cincinnati Contemporary Arts Center director Dennis Barrie, who was accused of promoting pornography by presenting an exhibit of photographs by Robert Mapplethorpe that included images of naked children and graphic displays of homosexual sadomasochism.

Dog Day Afternoon: Dog Day Afternoon is a 1975 American crime drama film directed by Sidney Lumet, written by Frank Pierson, and produced by Martin Bregman and Martin Elfand.  The film stars Al Pacino, John Cazale, Charles Durning, Chris Sarandon, Penelope Allen, James Broderick, Lance Henriksen, and Carol Kane.  The title refers to the sultry "dog days" of summer.

Frank Pierson: Frank Romer Pierson (May 12, 1925 – July 22, 2012) was an American screenwriter and film director.

Digital darkroom: Digital "darkroom" is the hardware, software and techniques used in digital photography that replace the darkroom equivalents, such as enlarging, cropping, dodging and burning, as well as processes that don't have a film equivalent.

Supporting paragraphs: Frank Pierson Peter Tscherkassky
Answer: Peter Tscherkassky