Exposure & Optics
6 items
Standardized mathematical and optical metrics governing photographic exposure: geometric f-stop progression (√2 ratio), cinema photometric T-stops, ISO 12232 sensor sensitivity, Exposure Value (EV / ISO 2720), 180-degree cinema shutter angle, and Kelvin color temperature scales.
Items (6)
CompareCinema Shutter Angle & 180° Rule
6 specs
Shutter Angle (measured in degrees from 0° to 360°, originating from circular rotary disc shutters in 35mm motion picture cameras) is the cinematic standard for measuring exposure time relative to frame rate (Shutter Speed = Frame Rate × 360° / Shutter Angle). The universal '180-Degree Shutter Rule' (exposure time = 1 / (2 × Frame Rate)) delivers natural, organic motion blur that mimics human eye persistence.
Color Temperature & White Balance
7 specs
Color Temperature (measured in Kelvin / K, standardized under CIE illuminant standards) defines the spectral chromaticity of light emitted by an idealized black-body radiator. Governing camera white balance, it ranges from warm Candlelight (1800K) and Tungsten Studio (3200K) through Photographic Daylight (5600K / CIE D55) to Overcast Sky (6500K / CIE D65) and Deep Blue Shade (8000K–10000K).
Exposure Value (EV)
6 specs
Exposure Value (EV, standardized under ISO 2720) is a logarithmic base-2 scale quantifying combinations of shutter speed and relative aperture that yield identical photographic exposures (EV = log_2(N² / t) at ISO 100). Governs light metering, auto-exposure compensation, dynamic range benchmarks, and the classic 'Sunny 16' outdoor rule.
F-Stop Scale
6 specs
The F-Stop Scale is a standardized geometric progression of lens focal ratios (N = f / D, where f is focal length and D is entrance pupil diameter) governed by powers of √2 ≈ 1.4142. Advancing one full stop (e.g. from f/2.8 to f/4.0) halves the cross-sectional area of the optical entrance pupil, cutting light transmission precisely in half (-1 EV).
ISO Speed Standards
5 specs
ISO Speed (standardized under ISO 12232 for digital sensors and ISO 6 / ISO 2240 for film, combining historical American ASA arithmetic and German DIN logarithmic scales) defines the sensitivity of an imaging medium to light. Operating on an arithmetic doubling progression (ISO 100 -> 200 -> 400 -> 800 -> 1600 -> 3200 -> 6400), each step doubles sensitivity, requiring half the exposure time (+1 EV).
T-Stop
5 specs
The T-Stop (Transmission Stop, standardized under ISO 517 for cinematography) is a photometric measurement of a lens's true light transmission (T = f / √Transmittance), correcting the theoretical geometric f-stop for physical light lost to glass reflection and optical element absorption. Standardized across all cine primes (Cooke, ARRI, Zeiss, Angénieux).