Imprinting information on film started in the 1960s, and every camera system with professional aspirations included an interchangeable camera back for date printing. These early backs were manual and really only of interest to technical users. Date printing only became popular in the late 1980s and early 1990s when LCD screens and quartz clocks became small and cheap enough to build into cameras and automate the setting and printing the date and time. Date printing was even built into cheap point-and-shoot models.
Cameras then were predominantly mechanically controlled so the backs were limited to data printing when the shutter fired. As shutters and shutter releases became electronically controlled it became possible for the backs to control the shutter release, so many of these command backs included interval timers for time lapse photography (when combined with motor drives to advance the film).
Gears and mechanical linkages were eventually replaced with electronics and Canon’s T90 released in 1986 was one of the first cameras with full electronic control of shutter, aperture, light metering and film transport.
Canon’s EOS cameras and EF lenses released in 1987 were a step above electronic, they were computerised: sensors, switches and servos replaced gears, escapements and mechanical linkages; digital CPUs calculated the necessary shutter speed, aperture opening and lens extension for correct exposure, focus and desired depth of field. All instantly and automatically without user interaction.
Enter the Technical Back E.
It’s fair to say that Canon’s EOS cameras were the most advanced available at the time, and Canon’s Technical Back E was developed to add further to their capabilities.