Auto-focus technology revolutionized the world of photography, making it much easier to take sharp, clear images without the need for manual focusing. This technology was initially developed for use in film cameras, which were the primary type of camera available at the time.
Auto-focus on film cameras typically worked by using an array of sensors to detect the distance between the camera and the subject being photographed. These sensors would send signals to the camera's processor, which would then adjust the focus of the lens accordingly.
There were two main types of auto-focus systems used in film cameras: active and passive. Active auto-focus systems emit a beam of infrared light that is reflected off the subject being photographed and then detected by the camera's sensors. Passive auto-focus systems rely on the camera's sensors to detect contrast in the image and determine the distance to the subject based on this information.
Both active and passive auto-focus systems had their advantages and disadvantages. Active systems were generally faster and more accurate, but required the use of a special flash unit to emit the infrared light. Passive systems were slower and less accurate, but did not require any additional equipment.
The first film camera with auto-focus technology was the Konica C35 AF, introduced in 1977. This camera used an active auto-focus system and was able to focus on subjects as close as 1.4 meters away. Other camera manufacturers quickly followed suit, with Canon introducing the AE-1 Program in 1981, which featured a passive auto-focus system.
As technology improved, so did the speed and accuracy of auto-focus systems in film cameras. In the 1990s, cameras such as the Nikon F5 and the Canon EOS-1N introduced advanced auto-focus systems that were able to track moving subjects and adjust focus accordingly.
In conclusion, auto-focus technology on film cameras worked by using an array of sensors to detect the distance between the camera and the subject being photographed. These sensors would send signals to the camera's processor, which would then adjust the focus of the lens accordingly. Both active and passive auto-focus systems were used, with active systems emitting infrared light and passive systems relying on image contrast to determine distance. The first auto-focus camera was introduced in 1977, and as technology improved, auto-focus systems became faster and more accurate. Sources for this information include camera manuals and technical specifications.