Sense Up is an image processing technology which allows user selectable digital slow shutter speeds. Also referred to as: Sens-up, Sensup, Sense-up, DSS or Digital Slow Shutter. It extends the light measurement time by the camera sensor thereby providing higher sensitivity in low light conditions.
Fig. 1. Example images taken using Sense Up
The main purpose of the function is to extend the light measurement time for each pixel of the camera sensor. This means that cameras are capable of seeing in near total darkness while retaining full-colour images. CCTV cameras equipped with this technology use an adjustable electronic shutter to vary the light measurement time.
In low light conditions, the camera enables Sense Up detection mode. Depending on camera’s settings and parameters, it superimposes a certain number of images and increases the brightness to produce sharper images.
However, if the image is dynamic, the moving objects on the image can be blurred. Due to insufficient brightness of the scene, the camera records several blurred images. The electronic processing at the output allows to produce a clear image with sufficient brightness. Clear images can be produced at low Sense Up settings (2x to 8x amplification).
Camera with Sense Up function is the best solution for museums, observation of nocturnal animals, and other static areas where use of artificial light sources (e.g. IR or UV) is not allowed.
One of the most important parameters is the Sense-up limit. The limit setting can be set on most cameras 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, it is highly recommend not going beyond an 8X amplification setting.
A camera and its display (DVR) have to sync in order to display proper images without distortion or interlace issues. The camera is providing 25 fps, and the recorder is receiving the exact same 25 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 25 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 incorrect syncing.
This changes altogether when there is a moving object in the image, and the faster the object moves, the more it is blurred. Also, the higher the Sense Up limit, the more the objects are blurred.
A partial solution to this problem in facial or license plate recognition systems is creating a place where vehicles or people have to stop. Remember, as long as the car or the person is not moving, the image will be crisp and clear, even in almost zero light. 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.