Instructions
Install a fully charged battery and an empty memory card into the Canon Digital Rebel XSi. Turn the camera on by sliding the power switch on the top right of the camera to the on position.
Rotate the exposure mode dial located on the top right of the camera to "Av" for Aperture Priority mode. In this shooting mode the photographer controls the lens aperture and the camera selects a corresponding shutter speed for the best exposure. By controlling the aperture, the photographer controls the depth of field of the image. A smaller aperture gives a greater depth of field where more of the image will be in focus.
Hold the camera to your eye and position the focus point on the middle person or row of people in the picture. If there are five rows of people in the picture, you want to focus the camera on the middle row. Press the small button located on bottom front right of the lens mount housing on the camera. This is the depth of field preview button. When pressed you will be able to see exactly how much of the image is in focus.
Turn the input dial near the shutter release to increase the aperture number, making it a smaller aperture, until the all the people in the group picture are in focus. When done, release the small button, press the shutter release to re-focus the camera. Press the shutter release all the way down to take the picture.