In this manuscript we examine the characteristics of holograms that are captured using both Fresnel and lens-less Fourier digital holographic systems. We begin by introducing some of the fundamental equations describing the intensity distribution captured by the camera. Naturally this captured intensity will vary depending on whether the system used is a Fourier or a Fresnel due to the different reference field in each case, however as we shall see with appropriate numerical processing it is possible to obtain similar performance from both systems. We discuss a reconstruction algorithm for changing the focus depth in Fourier holograms and examine how it effects the twin image and dc terms. A theoretical comparison with Fresnel holograms is made. Experimental results are provided to support our analysis. We finish with a brief conclusion.