An illustrated story about how Canon went from 6-zone metering sensors (1987) to their most advanced 216-zone 400,000-pixel RGB+IR metering systems (2020).
Providing only two additional metering zones compared to the proven 6-zone metering system, this 8-zone evaluative metering system didn't seem particularly innovative at first glance. However, according to technical brochures from 1990, this 8-zone evaluative metering system is more sensitive and more sophisticated than previous technologies. The Canon EOS 10 / EOS 10S was the first SLR camera to incorporate Canon's AIM (Advanced Integrated Multi-point control) system. This system linked focus and exposure in a sophisticated new way: The AIM system detects which autofocus point is on the main subject (usually the nearest) and calculates exposure specifically for that subject. Since microprocessors were still relatively new at the time, the technical journals placed particular emphasis on this new way of computer-controlled exposure metering.
The Advanced Integrated Multi-point control (AIM) system is a linked system that links focus, metering, and flash firing together. The focusing system tells the exposure metering system where to make accurate analysis, even if the subject is not in the center of the frame. At the time, this was a major improvement in flexibility, since before the AIM technology, photographers always had to use the central AF point for exposure metering and then recompose the shot.
This metering system provides optimal coverage of the cameras' three autofocus (AF) points. Zones 1-3 are each linked to an AF point, zones 4-6 offer light metering in the area directly surrounding the AF points, and the outer zones 7 and 8 cover the remaining viewfinder image. These metering zones are invisible to the user.
This 8-zone metering system offers the following metering modes: 8-zone evaluative metering and partial metering (zone 1) which covers approximately 9% of the central picture area.
The overall sensor design is very similar to its predecessors. Support structures, connector pins, as well as the integrated circuit (IC) die are embedded inside a clear-molded package. This sensor uses an 8-zone segmented SPC (silicon photocell) as the actual light-sensitive element. Some of the IC's active area surrounding the SPC is used for signal amplification and processing. The amplification circuitry allows the camera to use auto-exposure metering even in low-light situations.
EV -1 - 20 at ISO 100.