You can use FE (Flash Exposure) Lock with Type-A cameras. This is the flash version of AE Lock. With FE lock you use spot metering to obtain the correct flash exposure reading for a specific part of the subject.

• FE lock works with E-TTL and high-speed sync (FP flash)

Select a picture-taking mode with the camera Focus on the subject Press the FEL button Aim the viewfinder's spot metering circle over the port of the subject to be metered. Then press the <FEL> button on the camera The 550EX fires a preflash to obtain an exposure reading. The reading is retained in memory The focusing point linked to the FE lock lights red FEL is displayed in the viewfinder for 0.5 sec. You can also press the <FEL> button again to obtain an FE-lock reading for another part of the subject To cancel FE lock, wait until 16 sec. elapse or press the <MODE>, <AF> or < > button on the camera Recompose the picture as desired Check that the subject distance is within the flash range displayed on the 550EX's LCD panel Check the flash exposure level in the viewfinder, then take the picture

• If the subject is too far away to obtain a correct flash exposure, will blink in the viewfinder. Either mover closer to the subject or use a larger aperture (smaller f-number) and try again
• FE lock cannot be used if the 550EX is set to the M (manual) flash mode. With the EOS Elan IIE / 50E / 55 and the EOS IX the blinks in the viewfinder to warn that the FE lock cannot be used in the M flash mode
• The FE lock's preflash fires at about 1/32 output
• With Type-A cameras other than the EOS-1D, !v and 3, the AE lock button functions as and FE lock button when the 550EX is recharged and ready
• If the subject is small, using FE lock might not make any difference