Several factors come into play when setting up a CCTV security camera system that is right for you. You must determine where the system will be installed, how many cameras you will need, the type of camera, which DVR you want, how much storage space you will need, and much, much more. Something that shouldn't be overlooked but sometimes can be, is the resolution of the cameras themselves.
In the simplest of terms, resolution can be defined as the amount of detail an image holds. The higher the resolution, the better an image will be. When it comes to CCTV security cameras there are two main resolution types to be concerned with: TVL (Television Line) resolution and megapixel (MP) resolution.
TVL (Television Line) Resolution
TVL is used to measure the horizontal lines of resolution in analog security cameras. A more technical definition and example from Wikipedia.org states, “TVL is defined as the maximum number of alternating light and dark vertical lines that can be resolved per picture height...for example, a resolution of 400 TVL means that 200 distinct dark lines and 200 distinct white lines can be counted over a horizontal span that is equal to the height of the picture.” Take a look at the example below for a simple visual explanation.
TVL Example (courtesy of Wikimedia.org)
To determine the TVL of an analog camera, the long-running standard has been to use the EIA-1956 resolution chart (image below). All across the chart there are many different series of lines. These lines are marked with numbers that an individual can use to determine the TVL of their analog security cameras. Using an analog security camera to view the chart as an example, if you can clearly see the spacing between the lines at the 400 mark and 500 mark, but they become indistinguishable at the 600 mark; it is safe to determine that your analog security camera has a max resolution of 500TVL.
The EIA-1956 Resolution Chart (courtesy of Pbase.com)
Another type of resolution to take into consideration is megapixel resolution. This term can be applied to HD-SDI cameras and IP Cameras. According to Techterms.com, “A megapixel is one million pixels. It is commonly used to describe the resolution of digital cameras. For example, a 7.2 megapixel camera is capable of capturing roughly 7,200,000 pixels.” As with TVL resolution, a higher megapixel count means a higher quality image.
In the series below you can see how pixel count affects the quality of an image. The image on the far left contains only one pixel. This explains why it is one solid color. In the middle of the series, the image is comprised of 100 pixels. This is calculated by multiplying the 10 pixels in height by the 10 pixels in length. On the far right, the image contains 10,000 pixels. Once again, this is calculated by using the same multiplication principles of the previous image.
Pixel Demonstration (courtesy of Wikimedia.org)
What Does This All mean?
In the end, only the user can decide what what type of camera and resolution are the right fit for their CCTV security system. Sometimes you may want a better quality image, but you won’t necessarily need it. Other times you may want to save money with a lower resolution setup but you’ll find that you need a higher quality image to address your security concerns.