Exposure, Aperture & Photometric Standards
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
F-Stop Scale & Aperture Series (f/1.0 to f/22)
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 $\sqrt{2} \approx 1.4142$. 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).
6 specs
T-Stop (Transmission Stop / Cinema Standard)
The T-Stop (Transmission Stop, standardized under ISO 517 for cinematography) is a photometric measurement of a lens's true light transmission ($T = f / \sqrt{\text{Transmittance}}$), 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).
5 specs
ISO Speed Standards (ISO 12232 / ASA & DIN)
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).
5 specs
Exposure Value (EV / ISO 2720 / Sunny 16)
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 ($EV = \log_2(N^2 / t)$ at ISO 100). Governs light metering, auto-exposure compensation, dynamic range benchmarks, and the classic 'Sunny 16' outdoor rule.
6 specs
Cinema Shutter Angle & 180° Rule
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.
6 specs
Color Temperature & White Balance (Kelvin / CIE D50 & D65)
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).
7 specs