Designed for automatic operation only, the 220EX flash unit excels at providing natural-looking balanced flash exposures. When attached to the advanced cameras, such as EOS IX, EOS Elan II/Elan IIe, or EOS Rebel G, the 220EX delivers the benefits of the Canon's superior technology. These include Canon's unique E-TTL evaluative pre-stored flash exposure control system, FE Lock for a new dimension of creative control and FP Flash (high-speed sync) for flash photography up to maximum shutter speed. When used with other cameras, it operates as a TTL autoflash (off-the-film flash metering).When in E-TTL operation, flash exposure is measured and controlled by the camera in combination with Canon's AIM system. Subject position, ambient light level, evaluative metering and pre-flash data are instantly analyzed, including heavy backlighting or reflections from background windows or mirrors.