Do you use a large aperture (4.5?) to get a greater field of depth, so is this suited for landscape shots?
no, you would use a Larger number i.e. f11, 16 etc to get a greater depth of filed. smaller fstops for less DOF; however remember that DOF is also influenced by the focal length of the lens and the relationship of the camera to the point of focus.
Generally speaking, you want a significant DoF in landscape shots, so look towards smaller apetures, as ann mentioned, f11 ->
