7.5. E-TTL II

E-TTL II, introduced in 2004, is a refinement of E-TTL that brings two significant changes to the way Canon DSLRs perform metering. E-TTL II does not require any changes to either the flash units or lenses used with an E-TTL II camera—the changes are all internal to the camera body. Cameras that support E-TTL II always do so; there's no "fallback" to E-TTL. An older camera cannot be upgraded to E-TTL II.

7.5.1. E-TTL II's improved flash metering algorithms

E-TTL II examines the camera's central evaluative metering zones both before and after the E-TTL preflash goes off. Any areas with relatively small changes in brightness are weighted, or given greater priority. This reduces the E-TTL problem of reflective materials throwing off flash metering. The camera does not examine the metering zones around the periphery of the frame during flash metering, since it assumes that the subject will not be that close to the edge.