Set the camera's shooting mode to manual exposure mode (M), then set the desired aperture value and a shutter speed between 30 sec. and the camera's X -sync speed. Make sure the TTL indicator is displayed in the flash unit's LCD panel
Is for use with EOS-series film cameras. Do not set it if you have an EOS Digital camera or the EOS Rebel T2/300 X . If this custom function is set with such cameras, the flash control will not work properly.
The higher the flash output, the greater the maximum range. Use a hand-held flash meter or trial-and error to determine the correct aperture for a given flash-to subject distance. Once set, the exposure will remain the same as long as the distance and flash power level remain the same.
Option 2 limits the tilting to a straight-upward position of 90°, and no farther. This means that Full-auto Bounce will more often tend to tilt the flash upward but facing slightly toward the subject — a bounce position many experienced photographers are comfortable working with. And, as just mentioned above, this can help avoid possible errors if you are working in larger venues, where walls may be distant and not immediately behind the photographer.