Canon AE Light Metering Sensor Evolution

The History of EOS Light Metering Systems

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).

35-Zone Metering System

Cameras using the System

  • EOS 300 (April 1999) — 35mm film camera
  • EOS 30 (October 2000) — 35mm film camera
  • EOS D30 (October 2000) — APS-C DSLR camera
  • EOS D60 (March 2002) — APS-C DSLR camera
  • EOS 300V (September 2002) — 35mm film camera
  • EOS 10D (March 2003) — APS-C DSLR camera
  • EOS 3000V (September 2003) — 35mm film camera
  • EOS 300D (September 2003) — APS-C DSLR camera
  • EOS 30V (April 2004) — 35mm film camera
  • EOS 300X (September 2004) — 35mm film camera
  • EOS 20D (September 2004) — APS-C DSLR camera
  • EOS 350D (March 2005) — APS-C DSLR camera
  • EOS 5D (September 2005) — Full-frame DSLR camera
  • EOS 30D (March 2006) — APS-C DSLR camera
  • EOS 400D (September 2006) — APS-C DSLR camera
  • EOS 40D (September 2007) — APS-C DSLR camera
  • EOS 450D (March 2008) — APS-C DSLR camera
  • EOS 1000D (June 2008) — APS-C DSLR camera
  • EOS 50D (September 2008) — APS-C DSLR camera
  • EOS 5D Mark II (November 2008) — Full-frame DSLR camera
  • EOS 500D (April 2009) — APS-C DSLR camera

Why this System was Innovative

While the 35-zone metering system didn't really introduce a new technology, the number of metering zones was increased quite noticeably. The actual innovation to mention here is that this metering system was the first that arranged its light-sensitive zones in a uniform grid.

Metering Zone Layout

The metering zones are arranged in a grid of 7 columns and 5 rows, resulting in 35 metering zones of equal size. These metering zones are invisible to the user.

Metering Modes

This system offers the following metering modes: 35-zone evaluative metering, partial metering (five zones covering approximately 9% of the central picture area in a cross shape), and center-weighted average metering. Spot metering is available only on some of the camera models listed above (EOS 5D, EOS 5D Mark II, for example).

AE Metering Sensor Layout

The sensor consists of support structures, connector pins, and the integrated circuit (IC) die embedded inside a clear-molded package. This sensor uses a 35-zone segmented SPC (silicon photocell) as the actual light-sensitive part. 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.

AE Metering Range

EV 1 - 20 at ISO 100.

Back - 21-Zone Metering Main Menu Next - 63-Zone Metering