HD SDI cameras are high definition cameras that use a set of standards called serial digital interface (SDI) to transmit high definition video signals across coaxial or fiber optic cables to a digital video recorder (DVR) or other device. SDI allows for the rapid transmission of data at the high rates required by the camera’s much higher resolution. HD SDI is a standardized method for transmitting uncompressed, unencrypted video signals. The lack of compression means final images are sharper and more detailed than would be possible from a compressed feed. Although video compression saves on data storage space, and can be transmitted using lower bandwidth, it usually involves some loss of information. In contrast to video transmitted in the common MPEG format, for example, HD SDI video provides images that are sharper, have better color quality, greater image resolution, and more natural motion. A 1080p HD SDI camera delivers the sharpest, most detailed images possible, in the widescreen format most of us are familiar with from viewing HD television. 720p HD SDI cameras also deliver remarkably sharp, detailed images, with no loss of quality due to compression. Most home or office security surveillance systems include two or more HD cameras. Depending on the model purchased, modern DVRs are capable of capturing, displaying and recording four or more streams of video feed simultaneously. This makes it possible to monitor feeds from multiple cameras at the same time, giving the viewer a comprehensive view of the property’s perimeter and any internal cameras that may be set to monitor indoor activity—such as in a retail establishment, where it may be desirable to monitor customers or employees to deter potential theft.