When opting for network cameras, users often cite their numerous advantages over analog technology: easier installation, better total cost of ownership and better scalability, among many others. But what's often the most compelling advantage for users is the perception that the higher resolution of network cameras will provide better image quality and greater detail. While this theory is certainly true for megapixel and HDTV cameras, there are a few limitations you need to consider before deciding whether a higher resolution camera is the right choice for your application. Once you've weighed the pros and cons of using higher resolution technology, you will need to select which camera to use among the vast array of vendor models available today. A checklist at the end of this article will help you compare various manufacturer offerings.
The caveats of higher resolution
Though megapixel cameras are designed to deliver higher resolution, the greater detail comes with strings attached. The two main things you need to make a megapixel system work as promised are ample lighting and ample storage capacity.
- Low-light performance. High resolution image sensors contain more pixels than standard-resolution VGA sensors, but oftentimes are of similar physical size. The implication is that the sensor manufacturers simply reduce the size of each pixel to create more pixels per area. For example, a 1.3 megapixel sensor contains four times as many pixels as a VGA sensor, which also means that each pixel is only a fourth of the size of a standard pixel on a similar sized VGA sensor. The drawback of the smaller pixel size is that it reduces a sensor's ability to capture light. In other words, a typical megapixel sensor is less light sensitive than a standard VGA sensor. To achieve optimal performance you need ample lighting in the area under surveillance. In most indoor environments, such as schools, offices and retail stores where sufficient lighting can be guaranteed at all times, megapixel and HDTV cameras will work just fine. In environments with more challenging light conditions, such as a parking lot at night, a megapixel camera might not be sufficiently light sensitive. If it isn't, you may have to add illumination to the scene to get the most from your megapixel or HDTV camera, which will add cost and complexity to the project.
- Accommodating additional storage. Simply put: Greater image detail translates into larger image files. The math is pretty straightforward. If you're capturing four times the resolution of a standard VGA camera, you'll need four times the storage. So if you currently spend X dollars per gigabyte of storage, you'll need to increase your storage budget by a factor of 4X to archive video from each megapixel camera in your surveillance system. Additionally, the network traffic will increase by the same factor, which might be a challenge in some networks.
A comparison checklist
Once you've taken lighting and storage into consideration and decided that a megapixel or HDTV is indeed the right camera for your application, the next step is to evaluate which camera is the best fit for your environment. To ensure you're making an apples-to-apples comparison between vendor cameras, you need to consider the following:
Compression. As previously noted, megapixel or HDTV cameras generate a large amount of data. To avoid geometric expansion of your storage farm, efficient compression is essential. Ask your vendor if the camera you're considering supports the advanced H.264 compression standard. H.264 is a standard that can reduce the size of a digital video file by more than 80 percent compared with Motion JPEG, and by as much as 50 percent compared with MPEG-4 Part 2. Just as important, compare what compression format the camera supports when it is running at the highest resolutions and at high frame rates. Not all megapixel cameras can use H.264 when the camera is set for the highest resolution and highest frame rates; this is because H.264 requires a very highly-capable compression chip inside of the camera.