Security camera lines of resolution are one of the factors that determine the size, fineness, or quality of a high resolution CCD camera. Most often, this figure is referenced in TVL which stands for Television Lines and is usually used to reference analog type video quality. Digital resolution is usually referenced in terms of pixels. Let’s take a look at both and see how the lines of resolution relate to high resolution CCD camera picture quality.
First, there are different formats of video that are used in different geographical areas. NTSC (National Television System Committee) format is used in North and South America, Japan, and Taiwan and many other areas. PAL (Phase Alternating Line) format is used primarily in Africa, Asia, New Zealand, Australia, and the majority of Europe. SECAM (in French, SEquentiel Couleur A Mémoire, meaning Sequential Color with Memory) format occurs in parts of Africa and in the Russian Federation. Without getting too technical, we will just focus on the NTSC format.
A standard NTSC analog video is composed of 480 interlaced horizontal lines. The number of horizontal lines displayed must be counted vertically, one above the other and so on. Security camera resolution in TVL is a specification that refers to the horizontal resolution which is the number of vertical lines visible in a certain area of a monochrome picture. The number of vertical lines is counted horizontally, one next to the other and so on. Although TVL is not exactly equal to the number of scan lines, it is directly affected by the number of scan lines.
Most security camera video is displayed in a 3X4 aspect ratio. This means a display in the shape of a rectangle, 3 units wide by 4 units high. Since horizontal resolution is equal to the number of vertical units (lines), it is actually the measure of detail that can be seen in 75% or ¾ of the pictures width. TVL then is the number of vertical lines that take up the space of 3 units. In other words, on a picture that is 3 inches wide by 4 inches high with a TVL of 420, there are 420 vertical lines in the 3 inch width.
High resolution CCD cameras come in a variety of resolution specifications based on manufacturer, uses, and price, but for comparison purposes, a typical “standard” CCTV camera has a resolution of around 380 TVL while a typical “high-resolution” CCTV camera has a resolution of 540 TVL or higher. At the present time it seems that the highest resolution CCD camera can attain a resolution of 700 TVL.
The TVL resolution number is an indication of the actual inherent quality of a security camera or monitor and should not be confused with the actual horizontal scanning lines of broadcast television systems.
These lines of resolution apply to analog type video. Digital video resolution is somewhat different. Digital video is still displayed in a 3X4 aspect ratio. However, the resolution is measured in pixels (small points, dots, or squares). Like the analog cameras, digital cameras have a sensor, called a CCD or Charged Coupled Device that captures the picture in digital format. The digital picture resolution is referred to in terms of pixels such as 352X240 pixels. The three most common digital security camera resolutions include 704 x 480, 352 x 480, and 352 x 240 pixels.
Do not confuse the display resolution of the camera with the number of pixels of the CCD. The CCD sensor consists of millions of light sensing cells. The number of pixels produced by the sensor is called the pixel count. For example, a camera that can produce an image size of 640X480 would contain 307,200 pixels. A CCD capable of producing an image size of 3872×2592 would need to produce 10,036,224 pixels or 10 megapixels. This CCD rating in megapixels is often erroneously interpreted as the camera resolution. It more correctly indicates the maximum potential resolution the camera could produce when used in conjuntion with other high-quality equipment such as monitors, processors, etc.
To put everything in perspective, the following provides a summary comparison of both analog TVL and digital resolution with picture quality increasing as the number of the items increases:
1. 352X240 pixels (digital)
2. 330 TVL (analog)
3. 380 TVL (analog)
4. 480 TVL (analog)
5. 704X240 pixels (digital) and 704X480 pixels (digital)
6. 570 TVL (analog)
If you have any questions concerning high resolution CCD cameras please contact one of our security experts via on-line “Live Chat” or by telephone at 1-866-573-8878.