Shutter Speeds and Apertures

Shutter Speeds
If you are photographing fast moving objects such as cars or people running you need to select fast shutter speeds to capture the sharpest picture you can.Not only moving objects suffer from too slow a shutter speed. If you are holding the camera in your hand rather than having it mounted on a tripod, you will see the telltale signs of 'camera shake' (i.e. the movement of the camera) at shutter speeds longer than 1/125th of a second. A secure pair of hands will be able to get away with 1/60th or even 1/30th of a second but the camera would be better mounted on a tripod.Of course, if you are taking photos of static objects like houses with a camera mounted on a sturdy tripod, you can leave the shutter open as long as you want without blurring.

When the shutter speed is important as with moving objects, it's a good idea to set the camera to 'Shutter Speed Priority' mode. This is where you select the shutter speed and the camera selects the appropriate aperture according to the light reading.

Apertures
As well as letting more or less light into the camera the size of the aperture you choose governs the 'Depth of Field'. Depth of field means the amount of the picture, from foreground to background, that is in sharp focus. A smaller aperture will give you a greater depth of field and a larger aperture will give you a more restricted depth of field. This characteristic can be used to good effect in many ways.
If depth of field is important to either make sure everything is in focus or to throw some things out of focus, select the 'Aperture Priority' mode on your camera. In this mode you select the aperture and the camera selects the shutter speed according to the available light.