Let’s start this with a simple definition.
Sense-Up: An image processing technology which allows user selectable digital slow shutter speeds in order to allow extra light into a camera thereby providing higher sensitivity in low light conditions. Also referred to as “sens-up”,” sensup”, “sense-up”, “DSS”, and “digital slow shutter”.
If you are a CCTV or photography pro, this definition makes perfect sense. However, most people reading this article are probably not security or photography professionals and are wondering what this definition means in plain English. I will break down sens-up and explain the benefits and detriments of this technology when used in practical real-world surveillance applications.
The Benefits of Using Sense-Up CCTV Cameras The main purpose of sense-up is to provide a camera technology that does not rely on artificial light to see in very low light conditions. This means that cameras with sense up are capable of seeing in near total darkness while retaining full color images. Security cameras equipped with this technology use an adjustable electronic shutter to vary the amount of light that enters the camera. If you’ve ever been asked to take a dilation test at the doctor’s office you know that when we as humans encounter low light environments the iris of our eyes opens up in order to allow more light to be processed by our brains. You also know that when they dilate your pupils you will have a lot of trouble seeing in regular light for the next couple of hours. sense-up cameras operate in a similar fashion when they see darkness. The shutter stays open longer, allowing more light into the camera and seeing better in low light. There is one big difference however, when your pupils are artificially dilated, they remain dilated for quite a while, sensup cameras or cameras with DSS will automatically adjust back to normal settings in regular lighting situations. This sounds like the perfect technology, right? You retain the ability to see in high resolution during daytime, but gain the ability to see at night in stunning clarity and full color, who wouldn’t want their security camera system to work that well and be that versatile? Well, yes, it is a huge advancement in technology and usability, however, Sensup does have some drawbacks which will be discussed later in this article.
How does a DSS camera know how much adjustment to use? Well, most sense-up cameras have OSD, On-Screen Display. The OSD is used so that the installer can enter the camera programming menus and make adjustments to certain parameters. One of the most important parameters of sense-up cameras is the DSS or Sense-up limit. The limit setting can be set on most cameras anywhere from 2X amplification to 128X amplification. These settings translate directly into the amount of light being allowed into the camera, and not the actual shutter speed. For example, a 2X setting will allow 2 times more light than a standard digital shutter camera and a 16X setting will allow up to 16 times more light than normal. For reasons that will be discussed later, I highly recommend NOT going beyond an 8X amplification setting in the OSD menu for sense-up.
Many security marketing people claim that sense-up is the beginning of the end for infrared nightvision cameras, the holy grail of low light visibility. This is simply not true. Many of the best cameras I have seen are infrared sensitive Sense-Up equipped cameras which allow for a low sensup limit setting which still amplifies light quite a bit coupled with powerful infrared LED lighting to provide unbelievable low light performance for up to 300 feet in total darkness. DSS, or Digital Slow Shutter is definitely a valuable technology, but care must be used when relying solely on this technology to provide low light surveillance images. Extreme care must also be taken when vendors and marketers claim that their “version of sense-up” has no blur or streaking, or that their camera sees in total darkness without infrared lighting… this is simply not possible in the category of cameras most commercial applications can afford. It is however possible if you are willing to pay $5000 and up for each camera.
Why Sense-Up Is Not A Perfect Technology. When a sense-up camera adjusts its digital shutter to allow more light, it is essentially adjusting its internal sync. In order to understand what this means we have to dig deeper into the fundamentals of video technology. A video source (camera) and its display (monitor or DVR) have to sync in order to display proper images without distortion or interlace issues. Lets assume a real-time video situation providing 30 frames per second. The camera is providing 30 frames per second or FPS, and the recorder is receiving the exact same 30 FPS providing a properly synced video image. When a sense-up camera adjusts the shutter speed it is essentially allowing so much time for light to enter the camera between frames that it becomes impossible to send 30 frames every second. This is fine for static images where things don’t move very much. Each frame is the same as the next, so there is no movement in which we can see the evidence of the screwed up syncing. This changes altogether when there is a moving object in the image, and the faster the object moves, the worse the image appears. What you will see in this situation is best described as extremely blurry images. The DVR will capture up to 15 frames for every one frame the camera sends, and they will not be synced up properly. If you’ve ever seen a picture of an Indy car going 200 miles per hour, you know exactly what this looks like. This is a very cool effect for photography, but absolutely horrible for surveillance and security video.
The two variables that affect this sense-up related “blurriness” are the speed at which the object moves (the faster the movement the blurrier the video) and the amount of sensup limit in the OSD settings (the higher the limit, the blurrier the image under any movement whatsoever). It is for this reason that you do not want to use a sense-up camera for applications like license plate capture or other high movement areas. Faces will become blobs, license plates will be streaky and unreadable and if people are waving at the camera, they will appear to have multiple hands on the same arm. Quite amusing stuff, but I assure you, after you are reviewing your video for evidence of a robbery or other issue, the novelty wears off quite quickly.
If the user of the camera system can control human behavior, then a sense-up camera becomes a very beneficial technology. Examples of this use are creating a place where vehicles HAVE to stop and using a DSS camera to capture plates. Remember, as long as the car is not moving, the image will be crisp clear and color, even in almost zero light. Creating an entry barrier where a person must stop or enter an air lock, this accomplishes the same feat for facial recognition.
If the lighting is low, but adequate, a low sense-up limit and a high resolution camera can capture excellent images without blur or distortion, the trick is setting the camera up correctly and taking advantage of whatever ambient light does exist. However, if your environment has zero light, I would still highly recommend using a high powered infrared camera, if that camera has sens-up, a physical IR cut-filter or other low light enhancement technologies, then that’s even better.
More notes about DSS and sense-up: There are many names out there employing the Digital Slow Shutter Technology. Some of the more popular brands of sense-up cameras are the Illuminator Series cameras, Intensifier Series Cameras and ViZionCAM-RX Cameras, and NITE-WATCH from CCTV Dynamics. However, there are also versions of sense-up from Sony, Samsung, LG, and many other manufacturers. Prices vary wildly, so remember, sense-up is not the end all be all of low light surveillance, it is simply another tool to use in order to capture the best quality image you possibly can to aid in prosecution and prevention of crime.