All prism-based binoculars are similar, with four basic features that criminal justice agencies should consider when choosing a system. The first feature is magnification, expressed as a "power", and signifying how much closer the image will appear to the viewer than when observed with the naked eye. While beneficial to discreet surveillance, increased magnification results in a loss of light-gathering ability, a decreased field of view, and a decline in image stability. The second feature is the binocular's ability to gather and efficiently use ambient light. This is determined by the size of the objective lens, which will depend on whether the binocular is for day or nighttime use. An excess of light can cause eye strain. A larger lens requires a larger housing, increasing the overall size of the binocular, and increases the likelihood of reflections, which may reveal the surveillant's presence. Field of view denotes the width of the focused image as it appears through the eyepiece. A wider field of view tends to facilitate quick image acquisition. However, many wide-view binoculars lose image quality near the limits of the field of view. The fourth feature that potential users should consider is practicality, including the binocular's durability, size, suitability for a variety of surveillance needs, cost, and the reputability of the article's manufacturer and local dealer. Note