Low Light Performance
Before you choose which camera is right for a particular application, take a close look at the area you wish to monitor to get an idea of the lighting situation. Assessing low light performance depends entirely on whether the camera can handle your specific requirements. A camera’s light sensitivity is affected by a variety of factors including lens quality, aperture, the type of image sensor, exposure time, gain, and image processing. To simplify things, most IP camera manufacturers use a unit of measurement called “lux” to define the level of minimum illumination for a camera. The lower the lux number, the better the camera performs in low-light situations.
Of course there’s a difference between low light and no light. Even if a camera boasts superb low-light performance, at least some degree of ambient light has to be available, whether it’s from the moon, the stars, or a nearby street light. If the conditions truly are completely dark, you’ll need an IR illuminator or integrated IR LEDs in order to capture usable images.
Wide Dynamic Range
A security camera’s dynamic range is important to note, especially if you’re planning on monitoring areas where lighting conditions vary from one extreme to another. Examples include outdoor settings, and high-contrast or backlit scenes like you might find in a lobby. A surveillance camera with a wide dynamic range is able to address these difficult conditions by capturing quality image details in both bright and dark portions of the same surveillance area.
For surveillance applications where light levels can change frequently and drastically throughout the day, a security camera with an auto-iris lens is usually required. In outdoor locations, for example, auto-iris is essential because of the varying light conditions. An auto-iris lens automatically adjusts the amount of light entering the camera so it stays at the optimum light level and video images remain properly exposed at all times. For some megapixel cameras, an auto-iris lens isn't necessary.
Remember the days when surveillance footage most closely resembled the grainy reception of a yard-sale television set? Back then video surveillance wasn’t very effective because the images simply weren’t usable. But thanks to IP video technology, there’s really no limit to the amount of image detail today’s cameras can provide. Of course, every camera model has its own capabilities, and the amount of image detail required depends on the application. For license plate or facial recognition, for instance, a high level of image detail is essential. To determine the amount of image detail a camera can provide, look at the pixel count in the stated resolution. The more pixels a sensor has, the finer the details it can capture.
With analog CCTV cameras, image detail is measured in TVL (or TV Lines). The video picture is composed of active horizontal lines transmitted to a monitor or recording device. The horizontal lines are delivered in two off-set fields, one containing even-numbered lines, the other containing odd-numbered lines. These lines are then interlaced so the viewer sees a complete picture. Because the picture has a 3x4 aspect ratio, the horizontal TVL resolution refers to how much detail you can measure in 3/4 of the picture’s width. This number varies depending on camera type, but in general, standard CCTV cameras offer 380 TVL while high-resolution cameras provide 540 TVL.
A network camera with megapixel resolution is the preferred choice for applications where identification of people and objects is critical. Megapixel cameras not only capture exceptionally clear and detailed video images, but the high resolution also means they provide a much broader field-of-view than traditional security cameras. In fact, a single megapixel camera can monitor areas that would normally require multiple traditional cameras.
To get an idea for how megapixel resolution compares to that of analog cameras, consider that an analog camera, even after having its signal digitized by a video encoder, can only provide a maximum resolution of 720x480 pixels. Megapixel cameras start at around 1280x1024 pixels, and can get up much higher than that.
A key benefit of high-resolution, megapixel network cameras is they often provide digital PTZ functionality. Digital PTZ let’s you move around your field-of-view, and zoom in on specific parts of the scene while maintaining a high level of image quality. You can even record at full frame while simultaneously zeroing in on finite details. Essentially, it’s full pan/tilt/zoom functionality, but without moving parts, which provides the added benefit of extending camera life.
Unless you’re already a video surveillance expert, you’ll want to factor in how difficult it is to configure the camera for effective surveillance. Some cameras are ready to roll right out of the box, while others might require you to carefully adjust a multitude of settings. In the end it all comes down to your own comfort level, but typically, the less adjusting you have to do, the easier it is to avoid performance issues.
In the world of IP surveillance, Power over Ethernet (PoE) brings a great deal of flexibility to the installation process. IP cameras that support PoE receive their power via standard Ethernet cable. This same cable is also used for transmitting video and other data over the network. By integrating power into a standard LAN infrastructure, PoE effectively eliminates the need for nearby power outlets in camera locations, which means you can install your IP cameras virtually anywhere.