So, what does Automatic Depth of Field Mode do? Let's begin. These are the setting for my camera, but it will be about the same as yours as well. Do not worry ^^
Aperture = Auto
Shutter Speed = Auto
Exposure = Not Available
ISO Speed = Selectable
Picture Style = Selectable
White Balance = Selectable
AF Mode = Selectable
AF Point Selection = Not Available
Drive Mode = Selectable
Metering Mode = Selectable
Built-in Flash = Selectable
The objective of Automatic Depth of Field is to focus all subjects. Actually it sounds like compact camera to me because everything in target will be sharp and clear. The AF point is not selectable because all nine focus point well be in focused in order to capture close and everything clear picture. It works like Program AE but in different way.
A-DEP Mode is slightly similar with Close-Up Mode as well. The Aperture is in high f-number to narrow the depth of field. Therefore, all nine AF Point auto focus and narrow depth of field, it works just like "multi-focus" in compact camera. :)
By the way, since A-DEP Mode will automatically narrow the Depth of Field, the Shutter Speed will decrease in order to get enough Exposure. While you try to shoot a macro photography, slightly moved will cause blur result. Therefore, you are advised to use tripod or increase the ISO speeds.
However, users are allowed to control the picture style, white balance and etc to create special effect.