Elliptically shaped aperture opening instead of a circular form, producing characteristic oval lens flares and bokeh shapes.
Technical Details
Standard sizes for 35mm film range from 18x13mm (narrow oval) to 24x18mm (wide oval). The aperture is made of blackened metal or matte board with a precisely cut elliptical opening. The transition area (feathering) between the transparent and black area typically measures 0.5-2mm, depending on the desired degree of softness. Modern variants are realized as matte box inserts or as digital masks in post-production. Positioning is 10-15cm in front of the lens for optimal edge softness.
History & Development
First documented in 1903 in G.A. Smith's "Mary Jane's Mishap," the oval aperture experienced its heyday between 1910-1925. D.W. Griffith established it as a narrative stylistic device in "The Birth of a Nation" (1915) for close-ups and emotional climaxes. The technique almost completely disappeared with the advent of sound film, as the standardized formats of studio production did not allow for experimental masking. It experienced a renaissance in the 1970s with filmmakers like Hal Ashby ("Harold and Maude," 1971) and later with Wong Kar-wai ("In the Mood for Love," 2000).
Practical Use in Film
Classic application for portraits, key scenes, and memory sequences. In Buster Keaton's "Sherlock Jr." (1924), the oval aperture isolates the protagonist from his surroundings and enhances the dream sequence atmosphere. Modern productions use it sparingly: "The Grand Budapest Hotel" (2014) uses oval masks for nostalgic flashbacks. The light loss is 1-2 f-stops; the depth of field changes due to the reduced effective focal length. Digitally, the effect can be realized losslessly in DaVinci Resolve or Avid.
Comparison & Alternatives
Unlike the iris aperture with its circular opening, the oval shape emphasizes horizontal or vertical image composition. Soft mattes create similar effects without a fixed geometric shape. Modern alternatives include digital masks with animatable parameters or special anamorphic bokeh filters. Variable oval apertures with mechanical size adjustment exist for live productions but are rarely available.