Accessory Shoe 1 — For basic flash use with OM-1 or OM-2 bodies (no TTL automation; not for use with OM-1n or OM-2n) Accessory Shoe 2 — Only for OM-2. Offers TTL automation with Quick Auto 310 flash. Accessory Shoe 3 — Only for OM-2. Offers TTL automation with 'T' series flashes. Accessory Shoe 4 — Compatible only with OM-1n and OM-2n. Offers TTL automation with 'T' series flashes and LED 'ready' indication in viewfinder 以上擷取自:http://camerapedia.wikia.com/wiki/Olympus_OM_system