Surveillance camera technology has continued to improve and we will soon introduce a new model of cameras with a resolution of 4 megapixels to extend the capabilities of Internet Protocol (IP) based video surveillance systems.  We must not see this camera capability independently and must consider it in a system perspective.  

Many webcams have 1 to 2 megapixels.  Most still cameras have 4 to 10 megapixels.  We have heard of 50 megapixels too.  So what is special about 4 megapixels for a surveillance camera?   It is special and indeed a challenge for such a camera to transmit live footage over wire or wireless to a different location for display and storage, and for such footage to be ready for review after 7, 14 or 140 days.  The challenge is to preserve the clarity of the footage over distance and time. 

Suppose the camera transmits live views at 10 frames per second and we assume 1 pixel requires 8 bits to define its luminosity and colour, we will get 320 megabits or 80 megabytes per second (MB/s) of traffic for handling.  Suppose there are 10 such surveillance cameras on the campus, we will be dealing with 800 MB/s of video.  One day has 24 hours, one hour has 60 minutes, one minute has 60 seconds, and we will be dealing with 7TB of data per day or 49TB per week.  This numerical workload is a challenge but it is not yet the real challenge.

The real challenge is the generation of footage with a reproducible resolution of 4 megapixels.  This is a combination of camera lens, sensor, digital processing, compression, and transmission issues.  System A with Brand B of 4 megapixel cameras is totally different to System C with Brand D of 4 megapixel cameras. 

Some people think Megapixel IP cameras have over promised on their clarity advantage over standard analogue cameras that are about half a megapixel in resolution.  This is understandable because 4.0 divided by 0.5 should give us a factor of 8.  Our biological eyes are not as numerical.  We may say IP is clearer but are reluctant to say it is 8 times better. 

Furthermore the above scenario has assumed that the camera and the entire process of opto-electrical conversion, digital processing, compression, and transmission have taken place at 100% fidelity before the footage arrives in the computer.  We can assume so at a lower megapixel level but the accuracy will lose as the megapixel increases due to imperfection of design and manufacturing processes. 

We can apply the TV Lines counting technique to measure the clarity of footage, but it is a laborious process that can be done mainly by camera vendors and well equipped laboratories. For the rest of the population, we have to rely on trust and track records.  The purpose of this article is to inform as well as to set the level of expectation.  4MP does not fit all situations.  Feel free to contact the This e-mail address is being protected from spam bots, you need JavaScript enabled to view it for discussion.