The lens that the camera looks thru determines the picture that you see on the monitor. Lenses come in many different assortments. Whether it be the difference in focal length, F stop, auto iris or not, and/or having a motorized zoom or not. In short terms, the focal length determines the field of view (height and width of the picture). The F stop determines how much light is allowed to pass between the lens. The auto iris lens consists of a motor that opens or closes, depending on the amount of ambient light. Lastly, a motorized zoom lens allows for remote control of the focal length. If your having trouble selecting the right lens for you, please call us at (800) 572-3390 or visit us at the CCTVhelp.com forum for support