Security cameras are a vital part of any security system, and the quality of the camera images is crucial. Images must be clear enough to allow for identification, while being free of any elements that can obscure details. One measure of image quality is the camera TVL or TV lines and resolution.
But what does camera TVL mean? Is it the same thing as pixels? And what’s recommended for security cameras’ TVL resolution?
What is resolution?
Before answering the question, “What is TVL in cameras?,” it’s essential to understand the concept of resolution. When talking about security cameras, resolution refers to the quality of an image. An image with a higher resolution will be clear and sharp and provide more detail than an image with a low resolution.
What is TVL in cameras?
TVL stands for television lines: a measure of an image’s resolution displayed by an analog monitor or recorded by an analog camera. TV lines measure resolution by counting the number of alternating black and white vertical lines displayed on a monitor/video screen while remaining clear and defined.
In security, most businesses use a higher-level TVL camera, meaning a higher recording resolution of the camera. For example, 1000 TVL security cameras such as PTZ cameras can record images with 1000 clear and distinct lines of resolution. The number of TV lines a camera can record is determined by the sensor type and lens quality, among other factors.
Surveillance cameras’ TVL ratings range from 380 TVL to 1200 TVL. However, even though the camera has a 900 TVL resolution, for example, the resulting image may have a different resolution due to limitations of the rest of the system.
TVL is also affected by the encoding and formatting system used to transmit it, namely PAL (Phase Alternating Line), NTSC (National Television Standards Committee), or SECAM (Séquentiel Couleur Avec Mémoire). However, it is not the same as horizontal scanning lines. These systems employ 625 lines for PAL and SECAM, and 525 for NTSC.
How is TVL measured?
TVL is frequently measured using a TVL resolution chart known as the EIA 1956 Resolution Chart. This chart has a series of black-and-white lines that gradually get closer together. The number of TVL is equal to the number of lines on the chart that are still clear and distinct.
The measurement process involves setting up the chart at a known distance from the camera and recording it. The resulting footage is then played back on a monitor and paused at the point where the lines blur together. The number of TVL equals the number of horizontal black and white lines that are still visible and distinct.
It’s essential to use a high-quality monitor when conducting this test, as a lower-quality monitor may not be able to display the number of lines necessary to measure the TVL accurately.
TVL measurements are taken for a square equal to the display picture height, eliminating the aspect ratio issue. In other words, for a display that is 8 inches wide and 6 inches high (4:3 aspect ratio), the lines would be counted over 6 inches rather than 8.
If the monitor features a 600 TVL resolution, that would mean that 300 black vertical lines and 300 white vertical lines are drawn over a 6‑inch width, for a total of 600 lines.
Most common TV lines vs. pixels: What’s the difference?
Since TV lines and pixels measure the same thing, you might wonder what the difference is. The main difference between TVL and pixels is that TV lines measure a camera’s ability to resolve detail in analog systems, while pixels are a unit of measurement for digital images.
Comparing 600, 700, 900, 1200 TVL vs 1080p
Camera TVL uses lines across the display to measure resolution, and is commonly seen in legacy analog security camera systems.
On the other hand, pixels are the tiny dots that make up digital images. For example, a camera with a pixel count of 2 megapixels (MP) would have 2 million pixels. Therefore, the resolution of an image is determined by the number of pixels it contains.
For example, a 640 x 480 image has a resolution of 640 pixels wide by 480 pixels high, for a total of 307,200 pixels. A 1280 x 720 image has a resolution of 1280 by 720, or 921,600 pixels.
To put it simply, TVL vs MP (megapixels) is an analog vs digital camera resolution measurement. So, when it comes to 1200 TVL vs. 1080p, they are both measures of image resolution, but 1080p is a digital measure while 1200 TVL is an analog measure.
System TVL vs. camera TVL
When considering a security camera for your business, it’s important to understand the difference between system TVL and camera TVL. System TVL measures the entire CCTV system’s ability to resolve detail. In other words, it’s the sum of all the factors that affect image quality, including the camera, DVR, monitor and security camera cabling.
So, system TVL is what you’ll see on your monitor, while camera TVL is the quality of the image the camera can capture. System TVL is dictated by the weakest link in the chain.
For example, a camera with 1200 TVL resolution will only produce images with that level of detail if it’s recorded by a DVR with the same or better resolution. If the DVR only has a 700 TVL resolution, the images from the security cameras will only be displayed with 700 TVL of detail, regardless of the camera’s resolution.
Unfortunately, analog DVRs go up to a maximum of 720 TVL. So, a camera with 1200 TVL will only be able to display at 720 TVL when used with an analog DVR.
If you want to take full advantage of a 1200 TVL camera, you’ll need to use an HDCVI, AHD, or IP system, which can support up to 1080p (2‑megapixel) resolution. However, after all the hassle of connecting analog to digital, you will still not achieve the quality that a digital camera can provide. This is why many businesses are choosing digital and commercial IP security cameras over TVL security cameras.
Understanding resolution and security cameras
Security cameras are categorized into three basic transmission standards:
- Standard definition or SDTV
- High definition or HDTV
- Internet protocol or IPTV
Standard definition CCTV, or closed-circuit television, transmits an analog signal (or composite video) over point-to-point coaxial cable.
HD CCTV cameras transmit uncompressed digital data using the Serial Digital Interface (SDI) protocol over point-to-point coaxial cable. This allows for a high-quality image to be transmitted without any degradation in quality.
Internet Protocol (IP) CCTV systems consist of several IP cameras connected to a network switch via Ethernet cables. The images from the cameras are compressed and transmitted in the form of digital data over the Ethernet network.
Any analog broadcast is now considered SDTV because it doesn’t generate an image with high pixels. However, these TVL cameras can also be classified by their level of resolution.
For example, a 380 TVL camera is considered low resolution, while one with over 480 TVL would be considered high resolution. Anything with 504 TVL or above is DVD standard and would be regarded as very high resolution.
So, even though 600 TVL cameras and 1200 TVL cameras would be regarded as very high resolution, they already start from a low bar as they are all SD. In other words, 600 TVL vs. 700 TVL is not that significant of a difference, and compared to an HD camera, the quality will be poor, even if they are classed as high resolution.
Advantages of IP cameras over analog TVL cameras
With the modernization of video security, IP cameras are now the preferred choice for security and CCTV installations because they offer several advantages over analog such as PTZ analog cameras.
The most significant advantage of IP cameras vs analog is that they can transmit digital data over long distances without losing quality. This is because the data is sent in digital form, which can be compressed and transmitted more efficiently.
Comparatively, analog TVL cameras transmit an analog signal susceptible to interference and degradation over long distances. The result is a loss of image quality.
IP cameras also offer a much higher level of resolution than analog cameras. For example, you can get 4K IP cameras that provide 8 megapixels of resolution, which is four times the resolution of HD CCTV cameras and 16 times that of SD CCTV cameras.
You can also connect IP cameras to LED video surveillance monitors, ensuring you can see all the details the camera can record. Regarding image quality, IP cameras offer much more detail and clarity.
IP cameras also offer several other advantages, such as the ability to remotely view and control the camera, support for Power over Ethernet (PoE) and integration with third-party security systems.
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What’s the best TVL resolution for a security camera?
The simplest answer to this question is that because digital cameras now offer superior image quality, most new security systems greatly favor MP-based cameras over analog TVL security cameras.
For example, a camera with a 600 TVL resolution will never match the quality of a 2‑megapixel IP camera.
If you’re looking for the best possible image quality, you should look at digital IP cameras. But if you’re stuck with an analog system, then the best TVL rating will depend on the rest of your system.
For example, if you’re using an analog DVR with a maximum resolution of 480 TVL, a 600 TVL will be of little use. You will be better off with a 480 TVL camera because that’s the maximum resolution that your DVR can handle.
Why you should upgrade from a TVL security camera system
As discussed in this guide, TV lines (TVL) measure the resolution of an analog CCTV camera. The higher the TVL rating, the better the image quality for surveillance purposes. However, as video surveillance technology has evolved, TVL is a metric used for older technology and simply cannot deliver results on par with digital camera technology.
While analog security cameras might still be available on the market, there are better choices for new installations. IP cameras offer advantages such as better image quality, easier installation, and remote viewing and control.
If you currently have an analog setup with security cameras using TVL, it’s recommended to consider upgrading to a digital platform. Not only will you see better image quality from 1080p vs. 1200 TVL cameras, but you’ll benefit from greater capabilities, powerful analytics, and compatibility with a wider range of LED video surveillance monitors and third-party physical security systems.
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