Aperture setting midway between two full f-stops (e.g. f/2.4 between f/2 and f/2.8) for precise exposure adjustment without changing ND filters.
Technical Details
Half stops are found at f-numbers such as f/1.7, f/2.4, f/3.4, f/4.8, f/6.7, f/9.5, and f/13.5. Modern cinema cameras like the ARRI Alexa or RED V-Raptor support third-stop increments, allowing for even more precise settings. The iris mechanism of professional cine lenses enables stepless aperture adjustment through motorized follow-focus systems. On manual photo lenses, half stops can be set using intermediate positions on the aperture ring, while modern electronic lenses interpolate these values digitally.
History & Development
The concept of the half stop evolved in the 1950s alongside the introduction of more precise light meters in cinematography. In 1961, Kodak established more accurate exposure standards with its Vision film stocks, which required finer gradations. The German Society for Cinematography (DKG) standardized half and third stops for European productions in 1967. With digital technology starting in the 2000s, continuous aperture adjustments became the standard, as sensors react much more flexibly to exposure changes than film material.
Practical Application in Film
Roger Deakins systematically used half stops in "Blade Runner 2049" (2017) for subtle depth-of-field transitions between close-ups and establishing shots. Emmanuel Lubezki worked with third and half stops on "The Revenant" (2015) to achieve optimal exposure with available light without destroying the natural mood. Half stops allow for precise adjustments in changing lighting conditions during long Steadicam movements or during dialogue scenes with actors of different skin tones.
Comparison & Alternatives
While full stops are sufficient for basic exposure corrections, half stops offer fine-tuning without the need to change ND filters. Third stops provide even more precise control but extend setup times on set. Modern cameras compensate with variable ISO values (320, 640, 1250) in half or third increments. Stepless ND filters serve as an alternative, but they can cause color shifts. LED panels with continuous dimming are increasingly replacing mechanical aperture correction in controlled artificial lighting.