Canon Speedlite 600EX-RT Instruction Manual - Page 26

7: FE Lock FE (Flash Exposure) lock locks the correct flash exposure setting for any part of the scene. While is displayed on the LCD panel, press the camera's button. On cameras without a button, press the or (AE lock) button. 1 Focus the subject. 2 Press the button. (2) Aim the center of the viewfinder over the subject and press the button. X The Speedlite fires a preflash, and the flash output required for the subject is retained in the memory. X "FEL" will be displayed in the viewfinder for 0.5 sec. Each time you press the button, a preflash will be fired and the new flash output required at that time is retained in the memory. If a correct exposure cannot be obtained when FE lock is performed, blinks in the viewfinder. Move closer to the subject, open the aperture, and perform FE lock again. You can also increase the ISO speed and perform FE lock again when using a digital camera. If the target subject is too small in the viewfinder, FE lock might not be very effective. 24