We recently carried out an Interview with Todd Rockoff of the HDcctv alliance . We asked a number of questions that we will serialize over the next two weeks. We wanted to know how the HDcctv alliance was making progress and what is being planned and what we can expect in the next two years or so. We started by asking Todd our first question about HDcctv lenses. The answer is comprehensive and will give CCTV installers a good insight into what they will need to specify.
1 ) Todd, when it comes to lenses there currently seems to be few
guidelines. What lenses are the correct lenses to use – will the
alliance regulate or at least stipulate the required lens
specification for use with HDcctv cameras?
HDcctv lenses. What is the correct lens you need?
TR: HDcctv is an electrical/mechanical interface standard for connecting devices within a secured site. An HDcctv interface transports an HDTV signal without any degradation. HDcctv compliance is a property of devices (such as cameras, repeaters, IP encoders, DVRs, and monitors) and not of their individual components. That approach allows manufacturers maximum flexibility in designing those products. As a result, the HDcctv standard does not directly constrain lens characteristics in any way.
HDcctv compliance guarantees 100% multi-vendor interoperability, but as with analogue CCTV cameras, manufacturers compete on video quality. The lens, the image sensor, and the image signal processor (ISP) all contribute to a camera’s video quality. The lens is an integrated component in dome cameras and board cameras.
The HDcctv Alliance plans eventually to define “HDcctv 1080″ and “HDcctv 720″ compatibility levels, with associated certification tests. The idea is that an “HDcctv 1080″ compatible camera, for example, would measure a full 1920 x 1080 pixel array in each frame. If any camera component, including the lens, lacked sufficient resolution, then a 1080 or 720 compatibility certification could not be obtained.
For an HDcctv box camera today, it makes sense to choose a CS-mount lens of appropriate resolution. Be careful never to fit an old CCTV lens to an HDcctv camera! The result would be fuzzier video than necessary, failing to take advantage of the high-definition sensor and ISP. Similarly, to the extent that higher-resolution lenses are more expensive, there may be no need to fit a very high resolution lens to an HDcctv camera, because that would be overkill. On the other hand, some buyers find better results with slightly over-spec lenses. For example, sometimes a lens rated at 5 megapixels might give better results than a lens rated at 3 megapixels for a 1080p25 camera, whose native resolution works out to 2.2 megapixels.
I wish there were a more prescriptive approach to lens selection. Ultimately, just as buyers find their own comfort levels with camera price and performance, so should buyers explore price/performance tradeoffs in lenses for HDcctv cameras. One thing is for sure: product availability continues to grow, so there are plenty of alternative HD lenses from which to choose.
We say…………….So the above guidance on HDcctv lenses will help CCTV installers make some informed decisions on lens choice in order to get the very best images out of HDcctv systems. More questions we have put to Todd will be published soon but if you have any comments or feedback on HDcctv lenses please let us know.