|Type||550EX-dedicated, clip-on Speedlite transmitter with direct contacts|
|Compatible Cameras||Type A EOS cameras (E- TTL, autoflash); Type B EOS cameras (Manual flash)|
|Sync Speed||High-Speed Sync (FP flash): Enabled with high-speed sync mode|
|Flash Exposure Confirmation||1. Before flash fires during FE lock Adequate flash exposure indicated by the flash exposure level icon lit in the viewfinder. Insufficient flash exposure indicated by the flash exposure level icon blinking in the viewfinder.
2. After flash fires ST-E2's flash confirmation lamp lights in green for 3 sec.
|AF Assist Beam||Compatible with EOS-3's 45-point Area AF and 28mm and longer lens focal lengths
Effective Range: Approx. 0.6 to 10m/2.0 to 16.5 ft along the periphery (in total darkness).
|Transmission System||Infrared pulse|
|Transmission Range||Indoors: Approx. 12-15 m/39.4 - 49.2 ft; Outdoors: Approx. 8-10 m/ 26.2-32.8 ft|
|Flash Ratio Control||For A:B ratio: 1:8 to 8:1, in half- step increments or 13 steps|
|Flash Coverage||Transmission Coverage: +/-40 degrees horizontal and +/-30 degrees vertical|
|Slave Operation Confirmation||With test transmission button.
*Slave A fires followed by slave B at 1/64 output.
|Slave Unit SE Mode Cancellation||Cancels when the test transmission button or FE lock button is pressed to turn on the slave unit.|
|Power Source||2CR5 lithium battery x 1
Battery Life: Approx. 1,500 transmissions (At room temperature and with a new set of batteries)
|SE Mode||While the power switch is set to I or HOLD, the transmission turns off automatically after about 90 sec. of non-use.|
|Dimensions||62 (W) x 51 (H) x 80 (D)mm/2.4 (W) x 3.1 (D) in|
|Weight||100g/3.5 oz (exluding battery)|