May 20 2010
Research and consulting firm, Frost & Sullivan, announces its endorsement of the HTVL Effective specification, a new measurement technique for CCTV camera resolution.
The new specification uses the measured values of both horizontal TV lines (HTVL) and vertical TV lines (VTVL) to determine the true, useable resolution of CCTV cameras.
In the video security market, resolution is typically specified in HTVL. Although vertical resolution is rarely specified, it is equally important as horizontal resolution in calculating the total resolution of an image. Total resolution is the measured horizontal resolution multiplied by the measured vertical resolution. In the past, vertical resolution was rarely mentioned because of the limitations of interlaced image sensors; however, with the popularity of progressive scan imagers, vertical resolution is a critical component of total resolution, establishing the need for a new CCTV camera resolution specification.
Analog CCD sensors capture interlaced video using a process called line-pair summation. This technology has the side effect of decreasing vertical resolution by 25%. This decrease is unfortunate for end users, because DVR and display monitor inputs are very capable of accepting all 480 lines of vertical resolution. On the other hand, imagers that perform progressive image capture maintain the full vertical resolution thereby offering higher total resolution on initial display as well as during playback.
The dawn of digital image sensors, display devices, and recorders has reduced the meaningfulness of HTVL as a stand-alone resolution specification. Outside of the security industry, cameras are commonly specified using total resolution.
In response to industry trends and new technologies, Pixim Inc., a leading provider of imaging technology for enterprise security cameras, has proposed the new HTVL Effective (HTVL-E) specification which takes into account both HTVL and VTVL, expressed as a single resolution number for CCTV cameras. This new specification gives video security cameras full credit for the entire, usable image they produce while maintaining compatibility with traditional HTVL nomenclature. Use of the HTVL-E standard will enable end users and security consultants to compare the relative useable resolution of different cameras regardless of the image capture technology used.
Sandeep Maheshwari, Vice President of the Electronics & Security Group for Frost & Sullivan, explains, "The proposed HTVL Effective Specification is a much more relevant and accurate indication of the actual, useable resolution of CCTV cameras. In this age of digital image sensors, digital image processing, digital recording, and display, HTVL-E provides users of security video with more accurate information regarding their camera specifications and performance. The standard is simple to measure on any CCTV camera using any type of image sensor; thus, Frost & Sullivan endorses its broad use within the video security industry."