One of the most confusing and difficult topics in the CCTV world is
resolution. Most of us have digital cameras or video camcorders and have heard
the term megapixel used as the most common comparison in resolution between
various makes and models. We are also aware that a larger number means better
picture quality, but many people do not know why. In the CCTV security camera
world, though, most cameras are still analog and their resolution is measured
differently from what we are used to.
When measuring analog resolution, a TV line does not have a defined number
of individual pixels. Instead, the term “TV lines” refers to the number of
discernable horizontal or vertical lines on the screen. Analog security cameras
are measured in Analog TV Lines, and most of them have between 420 and 580. The
higher number of TV Lines, the more information captured. These types of
cameras connect to a security DVR or CCTV VCR via coaxial video cable.
Zoomed too far into a picture from a website and seen the image go from
clear to a bunch of colored squares – each one of those squares is an
individual pixel. A megapixel (MP) is 1 million pixels, and is a specific
measurement for digital resolution that encompasses the area of the output
video.
Example: If a camera outputs a signal that is 1280×1024 pixels, it is shooting at a megapixel resolution of 1280 x 1024 = 1,310,720 pixels = 1.3 Megapixels (MP).
The most common type of digital security cameras are IP Cameras. These,
like your digital camera at home, use strictly digital resolution. They utilize
a network connection to either act as a standalone device or connect to a
network-based DVR (Digital Video Recorder) or NVR (Network Video Recorder). IP
Cameras have fixed resolutions and are now approaching, and in several cases
exceeding, 1 megapixel in resolution, on average. Many of these cameras also
support POE (Power Over Ethernet), which allows them to be powered by the
Ethernet cable used for network connectivity, and PTZ (Pan Tilt Zoom), allowing
for remote control of the pan, tilt and zoom features, if applicable.
I hope this helped everyone distinguish the differences between Analog (TV
Line) and Digital (Pixel) Resolution. We would love to know what you think of
our articles, and if you have any further questions, don’t hesitate to leave a
comment!
21 comments:
Great post! I was looking across the web and came across these different resolutions for Analog and IP Cameras:
Type Horizontal Vertical Resolution
————————————–
CIF 320 240
VGA 640 480 VGA
WVGA 752 480 WVGA
SXGA 1280 1024 1 Megapixel
UXGA 1600 1200 2 Megapixel
QXGA 2048 1536 3 Megapixel
QSXGA 2560 2048 5 Megapixel
If these are correct, hopefully, they will assist in helping others learn the difference between Analog and IP resolutions.
- Sushanta
I like your expanation of this information. When is it best to use a megapixal camera over analog type? Is outdoor use ok for megapixal too?
Megapixel and better resolution IP cameras capture more detail in a given image than their analog cousins. This means if you set 1 of each type with the same lense size up to capture an identical view, the megapixel camera will have more image detail in its picture. another advantage to IP cameras is that they use CAT5 network cable and do not have to be directly connected to the DVR, many of them have thier own web server built in and can be viewed independant of a DVR. This is great for locations that just need one camera to purchase a standalone IP camera and connect it to their network and view from any PC on their network, and with just minor network configuration view it from any location on the internet. Some of them even have Software included to turn a PC into a recorder for the video.
In answer to your outdoor use question, there are some IP megapixel cameras that are designed for outdoor use and are vandal resistant. Others can be placed in weather resistant housings allowing for outdoor use.
- John
Firstly i want to say something about megapixel cameras and their outdoor usage: As far as i know that most of Mgpxl. cameras has low illumination levels so i don’t recommend them for fence security or sort of outdoor applications.At night or low light conditions they are not effective, if you need you should choose IP67 housing+ IR illuminators.
Another issue : Below information is taken from a white paper from my company, i have some extra information and graphical definitions about comparing TVL and CIF/D1 resolution etc. i’ll share with you if someone needs more info.
Resolution (TVL – or TV Lines) is a monochrome specification that states how many black and white lines can be seen in a given area. With 480 active scan lines, we can see how the theoretical maximum vertical TVL resolution is directly affected by the number of scan lines. (Note: TVL is not equal to scan lines, but vertical TVL is affected by the number of scan lines.)
A digital picture is made up of pixels that are basically just dots of light. From the examples you gave:
On the PVR the first number (640) would be the number of dots of light/pixels across the screen. The second number (480) would be the number of lines down the screen.
The cameras you listed will be something like 560x420 & 693x520 pixels (assuming a 4:3 picture)
-Mark.
Pixel count is only one element in a camera's capability to deliver visible details. Other critical ones include lenses, compression, frame rate, low light and WDR performance - some of which actually can be worse with more pixels. As such, resolution as 'pixel count' ignores critical elements in delivering real 'resolution'.
Pixels are like height in basketball. If you are too short or have too few pixels, you can never be the best at either. But being the tallest or having the most pixels does not ensure success. In basketball, a very tall person might lack coordination, athleticism, drive, intelligence, etc. just like a super high pixel count camera might be terrible in many other ways. More pixels can be useful but, just like height in basketball, smart 'scouts' should consider the whole package.
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