Exploring the Origins of Auto Mode: The Evolution of APEX System and Priority Modes | Release #376
Cover photo by shizuku
The modes such as 'Aperture Priority' and 'Shutter Speed Priority' have significantly changed camera operability. Behind these modes is the 'APEX System' developed in the mid-20th century.
By understanding the history and principles of this system, one can comprehend how modern photography technology has evolved and expanded creativity. This time, we introduce the changes and history of these systems.
The Mathematical Framework Supporting Photographic Expression
Born in the 1950s, the APEX (Additive System of Photographic Exposure) was devised to simplify exposure calculations. This system expresses aperture value (AV), shutter speed value (TV), and ISO sensitivity (SV) on a logarithmic scale, calculating the exposure value (EV) by adding them.
This concept made complex exposure calculations intuitively understandable, allowing for quick setting changes on the shooting site. Particularly, the mechanism of mutually adjusting AV and TV to maintain a constant EV forms the basis of later automatic modes.
Photo by saciiiko
The Emergence of Aperture Priority and Shutter Speed Priority Modes
The concept of the APEX system is directly applied to modern cameras' 'Aperture Priority (A/Av)' and 'Shutter Speed Priority (S/Tv)' modes. In aperture priority mode, the user sets the aperture, and the camera automatically adjusts the shutter speed, while in shutter speed priority mode, the reverse occurs.
Photo by bikkya
Additionally, the additive exposure control of APEX is also inherited in the exposure compensation and program mode calculation logic of digital cameras.
The Spirit of APEX Living into the Future
The principles of APEX influence the latest cameras incorporating AI and computational photography technology. For example, AI analyzes the entire scene and applies optimal settings to each part, enabling more advanced exposure control.
Photo by hhhiroooki
This evolution realizes the ideal of 'accurate and simple exposure settings' aimed by APEX in a new form. As a foundation supporting future photography technology, the APEX system will continue to play an important role.
