Stop

Technical Details

The aperture values follow a standardized series: f/1.0, f/1.4, f/2.0, f/2.8, f/4.0, f/5.6, f/8.0, f/11, f/16, f/22. Each stop reduces the amount of light by a factor of √2 (≈1.414). Modern cameras operate with 1/3-stops (0.33 EV) or 1/2-stops (0.5 EV) for more precise exposure adjustments. The mathematical basis is derived from the ratio of focal length to the iris's aperture diameter. For cinema lenses, the T-stop scale is often used, which indicates the actual light transmission value and accounts for lens losses.

History & Development

The stop system evolved from early 19th-century photography. In 1895, the Royal Photographic Society standardized the f-number notation. Its cinematographic application became established with the first professional film cameras around 1920. The introduction of T-stops by the Society of Motion Picture and Television Engineers (SMPTE) in the 1960s significantly improved accuracy in film productions.

Practical Application in Film

Cinematographer Roger Deakins frequently uses T/2.0-2.8 for his characteristic depth of field in films like "Blade Runner 2049". For outdoor daylight shots, T/5.6-8.0 are typically used, while night scenes often require T/1.4-2.0. Precise stop control allows for consistent exposure between different camera positions. Emmanuel Lubezki used constant T/2.8 settings for "The Revenant" to maintain the natural image mood with available light.

Comparison & Alternatives

Stops differ from ISO and shutter speeds in their direct mechanical influence on depth of field. While ISO changes affect image noise and shutter adjustments alter motion blur, the aperture remains the primary creative tool for depth of field control. Variable ND filters (Neutral Density) offer alternative light reduction without changing depth of field. Modern digital cameras allow for post-production corrections, but in-camera aperture selection remains crucial for optical image quality.