Just FYI, you got the depth of field definition backwards... an image in which only a small "slice" of the field is in focus is considered to have less depth of field, whereas an image in which a large portion of the field is in focus is considered to have more depth of field.

There are really two numbers, then, to consider in relation to aperture, the maximum and the minimum, and there are more reasons to consider aperture than merely depth of field.

Aperture materially impacts two things when shooting, depth of field, as has already been discussed, and, equally importantly, the amount of light let into the camera through the lens!

A camera, even digital, requires a certain amount of light to properly expose a picture. Too much light and the picture appears washed out, too little and it appears dark. Three factors come into play when determining the impact of light on the shot:

1. Film speed or "ISO" setting on digital cameras (how fast the film/sensor can pick up the light)
2. Aperture (how big of an opening the light travels through)
3. Shutter speed (how long the film/sensor is exposed to light)

This gives you several shooting combinations based on whether you want to shoot action photos, landscape photos, portraits, studies, etc. The trick is to understand what impact each setting will have on the picture. Higher ISO settings will result in grainier images but require less light to expose properly. Lower ISO settings result in cleaner/smoother images, but require more light to expose properly. A wide aperture results in a shallow depth of field for portraits, whereas a tight aperture results in much greater depth of field for landscape shots. A fast shutter speed stops motion and is great for action shots, whereas a slow shutter speed accentuates motion and is great for shooting things like waterfalls.

Sorry for the novel, but it is important to remember that you don't just use the aperture (or f/stop setting) to impact depth of field, but also to offset other settings like shutter speed and ISO setting, and depth of field goes both ways!

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