Megapixels vs TV Lines: Understanding CCTV Resolution
Megapixels vs TV Lines: Understanding CCTV Resolution
Megapixels and TV lines describe different aspects of image resolution. Knowing the difference helps when comparing a legacy analog camera with a modern surveillance system. Neither number, by itself, tells you whether a recorded face or vehicle will be clear.
What are TV lines?
TV lines, or TVL, express the horizontal resolving ability of an analog video system using alternating vertical light and dark lines. The measurement is normalized to a width equal to the picture height. It is not a count of the horizontal scan lines in a PAL or NTSC signal.
A TVL rating describes resolved detail in the analog signal chain. It is not the same as a camera sensor’s total pixels or the dimensions of a digitized recording.
What are megapixels?
A megapixel is approximately one million pixels. For a digital image, multiply its horizontal and vertical pixel dimensions to calculate the pixel count. Check the actual recording dimensions rather than relying only on a rounded marketing label.
| Image dimensions | Approximate pixel count |
|---|---|
| 1280 × 720 | 0.92 megapixels |
| 1920 × 1080 | 2.07 megapixels |
| 2560 × 1440 | 3.69 megapixels |
| 3840 × 2160 | 8.29 megapixels |
Full HD commonly refers to 1920 × 1080. A 16:9 aspect ratio describes the image shape, not a unique resolution. Many different pixel dimensions have that same ratio.
Can TVL be converted directly to megapixels?
There is no universal one-to-one conversion. TVL is an analog resolving measurement; megapixels count a digital image’s samples. Digitizer settings, signal quality, bandwidth, processing, and recording format affect the result. Avoid tables that present a particular sensor’s dimensions as a universal TVL equivalent.
Are all coaxial cameras low resolution?
No. Legacy composite-video systems and modern HD-over-coax systems are different. TVI, CVI, and AHD equipment can support high-definition formats when the camera, recorder, and cable installation are compatible. A BNC connector alone does not establish compatibility.
Read about HD-CVI technology and coaxial CCTV cable.
Why more pixels may not solve an image problem
Image resolution is only one part of the design. A wide view spreads the available pixels across more of the scene. Poor focus, difficult lighting, motion blur, and excessive compression can hide detail even in a high-resolution recording.
Define the target and viewing distance first. Then compare actual recorded footage at that location. Use our fixed and varifocal lens guide to understand framing choices.
Check the whole recording path
- Confirm the camera’s output format, resolution, and frame rate.
- Check what the recorder supports on each channel and in the selected operating mode.
- Verify the saved stream, not only a high-quality live preview.
- Test daytime, nighttime, motion, playback, and exported clips.
Continue with the CCTV camera buying guide or return to the CCTV FAQ.