ISO 516:2019

Overview

ISO 516:2019, "Camera shutters - Timing - General definition and mechanical shutter measurements," defines a uniform basis for determining exposure times and measuring mechanical shutter performance in still cameras. The standard provides precise definitions, required exposure-time markings and tolerances, and measurement procedures for mechanical shutters (both front shutters and focal‑plane shutters). It also covers characteristics that affect exposure control, motion‑stopping ability and synchronization with photoflash sources. Note: the prescribed test methods require access to the camera focal plane and therefore cannot be applied to fully assembled digital still cameras.

Key Topics and Requirements

• Terms and definitions: clear definitions for effective time, exposure time (measured at center), total time, shutter efficiency, fluctuation of exposure time, non‑uniformity of exposure, delay time, and synchronization contacts (X, M, FP).
• Exposure‑time series and markings: exposure times follow a binary series where each step changes time by a factor of two (one exposure step, E). Markings are specified as rounded reciprocal values (e.g., ...8, 4, 2, 1, 1/2, 1/4...) and common marked speeds (e.g., 15, 30, 60, 125, 250, 500, 1 000).
• Tolerances and target values: the standard specifies target tolerances for exposure time errors, fluctuations, adjacent‑step ratios and non‑uniformity. These tolerances are intended as target performance levels rather than a strict inspection regime-manufacturers may vary tolerances by camera class and feature set.
• Shutter types: distinguishes front shutters (expose picture area almost simultaneously) from focal‑plane shutters (expose incrementally via a moving slit) and gives formulas relating slit width, curtain velocity and exposure metrics.
• Photoflash synchronization: defines delay time and synchronization contacts (X, M, FP) and references ISO 10330 for ignition circuit details.
• Test methods and apparatus: prescribes apparatus (detectors, time‑interval meters) and procedures for front‑shutter and focal‑plane shutter tests. Annex A includes graphic test methods for routine manufacturing testing and quality control.

Practical Applications and Who Uses It

• Camera manufacturers use ISO 516:2019 to design, specify and validate shutter timing and synchronization for mechanical shutters.
• Quality control and test laboratories apply the test methods during production testing and routine verification (when focal‑plane access is available).
• Repair technicians and optical engineers rely on the standard’s definitions and tolerances when servicing or specifying replacement shutters.
• Standards bodies and certification labs reference ISO 516 when assessing compliance of photographic equipment.
• Advanced photographers and educators can use the standard to better understand shutter timing behavior and photoflash synchronization characteristics.

Related Standards

• ISO 10330 (photoflash ignition circuits) is referenced for synchronization circuit details.
• Produced by ISO/TC 42 (Photography); consult your national standards body for implementation and national adoptions.

Keywords: ISO 516:2019, camera shutters, shutter timing, mechanical shutter measurements, exposure time, focal‑plane shutter, front shutter, photoflash synchronization, shutter test methods.