Before purchasing your IP Cameras, it’s best to understand the specifications. IP Cameras have distinct advantages over the older analog cameras, but it’s not always easy to determine the right camera for each viewing situation. For example IP cameras are available with 640 x 480 (VGA) to 2592 X 1944 (5 megapixel) resolution. You certainly don’t need the 5 megapixel camera to view a doorway, so why pay for this extra performance. By reviewing your requirements and camera specifications you can match the camera to each viewing situation. New specifications have been added to the IP Cameras. Specifications to consider include the lens, resolution, light sensitivity, and dynamic range.
There are a number of different types of lenses. There are fixed focal length, and variable focal length lenses. There are lenses with manual iris and others with auto-irises. Some lenses must be adjusted at the camera, and some new lenses can be adjusted remotely. Here are more details:
Fixed Focal Point Lens: These lenses view a fixed area and you can’t adjust the zoom. They are available with manual and auto iris control. For example the Axis M1101 is a simple indoor camera with a fixed 4.4 mm wide angle lens. It costs under $170
Variable Focal Length Lens: Also called variable lenses, allow you to adjust the field of view by adjusting the focal length setting. These are better lenses since they allow you to make adjustments so that you are viewing exactly what you want. They are available with manual or auto iris.
Iris Control: The iris can be controlled manually or automatically. While it is true that a smaller iris opening often means sharper images, too small an opening may blur an image due to an optical effect called diffraction. This problem can be seen in bright outdoor situations when a camera closes the iris too much and light is diffracted or spread over many pixels. The smaller each pixel is on an image sensor, the more of a problem diffraction becomes because the diffracted light affects more pixels. This can typically happen in cameras that use an automatic DC-iris lens in combination especially with megapixel sensors that have small pixels. (While a megapixel sensor has more pixels than a standard VGA 640x480 image sensor, the size of each pixel on a megapixel sensor is often smaller than the size of each pixel on a VGA image sensor.)
Manual Iris Lens: These lenses are usually used indoors and allow you to adjust the iris opening.
Auto-Iris Lens: The iris of the lens is adjusted by the camera. The iris opening is adjusted automatically when more or less light is required on the sensor of the camera. They are usually required for outdoor cameras. Some IP Cameras like the ones from IQinvision, do not rely on the iris but rather make all the adjustments electronically. The Axis P3343-VE is an example of an outdoor dome camera with an auto-iris lens. This is a very nice camera since the zoom and focus can also be remotely controlled. You can remotely control the view from your computer. It costs less than $1000.
P-iris lenses: P-Iris is a new type of iris control that is both automatic and precise. It works in conjunction with the camera to improve the quality of the video. Unlike a DC-iris lens, the main task of the P-Iris control is not to continuously adjust the flow of light through the lens. The primary objective of P-Iris is to improve image quality by enabling the optimal iris position to be set so that the central and best-performing part of the lens is used most of the time.
The P-Iris works with the electronics of the IP camera. It not only adjusts the iris, it also adjusts the gain (amplification of the signal level) and exposure time. This allows it to manage slight changes in lighting conditions and to further optimize an image. This allows the optimal iris position to be maintained as long as possible. In situations when the preferred iris position and the camera’s electronic processing capabilities cannot adequately correct the exposure, a P-Iris camera will automatically instruct the iris to move to a different position. In dark conditions, for example, the iris will fully open. In bright situations, a camera with P-Iris is programmed to limit the closing of the iris to a position that avoids diffraction or blurring, as explained earlier. Hence, in all lighting conditions, P-Iris can automatically make adjustments to deliver optimal image quality.
Take a look at the two pictures below. You can see the benefits of the p-lens.
At the moment only Axis and CBC have this new functionality. The Axis P1346 and P1347 are examples of cameras with p-iris lenses.
Megapixel Lens: Megapixel cameras require megapixel lenses. These lenses are much clearer than the standard CCTV analog camera lens. They cost more so if you see two megapixel cameras with the same number of pixels but one cost much less, they are probably using a less expensive (not as good) lens. Take a look at our article on how High-Resolution, Megapixel Cameras are not all Alike.
The latest IP cameras have the very nice capability of providing much better resolution than the old analog cameras. You can select cameras with 640 x 480 (VGA) lines to 2592 x 1944 pixels (5 megapixels). The resolution of the camera starts with the sensor, but also includes the lens and quality of the processor and compression used in the camera. Take a look at our article High Resolution Cameras are Not all Alike for more about this.
With a higher resolution you can see a wider view. Take a look at the picture below. It gives you some idea of the different views you can see.
To determine what resolution you need, you first consider how wide an area you would like to view and then what detail you need in that field of view. For example, suppose you want to view a doorway and you want to be able to identify a person’s face that comes in the door. In this case you only require a 640 x 480 resolution camera. On the other hand, suppose you want to be able to identify a license plate number in a parking lot that’s 60 ft wide. In this case you need a lot more pixels, and will require a 5 megapixel camera such as the Axis P1347 or IQ755.
There are 3 types of compression used by cameras, MJPEG, MPEG4 and H.264. There is some debate about what the best type of compression.
MJPEG requires the most data, provides a complete picture for each frame. Many people say this provides the best resolution.
MPEG4 reduces the amount of data required by only sending the video that change between frames. It improves the compression when there are small parts of the picture that are changing.
H.264 is a version of MPEG4 and provides the best compression. It adds a number of other compression algorithms that dramatically reduce the amount of data transferred. The chart below gives you some idea about the improvement provided by the different compression schemes.
Most new cameras from Axis, IQinvision, Sony and others now provide this compression scheme. This compression uses a lot of computer resources so some high resolution cameras can only handle lower frame rates. As an example, the Axis P1347 provides 5 megapixel resolution and up to 12 fps when using H.264 compression. It sells for under $1499. For more details about the latest compression take a look at our article.
LOW LIGHT AND AMPLIFICATION:
Camera light sensitivity is measured in lux, which is the amount of light reflected from the object being viewed. The lower the lux number the darker the view. For example, 0.27 lux is the amount of light from a full moon on a clear night, while 500 lux is the light in an office.
The low light performance of a camera is determined by:
· The size and sensitivity of the sensor
· The F-Stop and quality of the lens
· The quality of the video amplifier in the camera
· Day/night capability
Sensor: The larger the sensor the more light hits it, so the higher the light sensitivity.
Quality of the Lens (F-Stop): The F-stop and quality of the lens determines how much light gets through the lens. The smaller the F-number the more light gets in.
Amplifier and signal-to-noise: The quality of the amplifier in the camera determines the video performance when there is low light. As the light level goes down, the amplification increases. The signal-to-noise (S/N) of the amplifier becomes important at the lower light levels. When the light level is too low, electrical noise reduces the quality of the video. The better the amplifiers in the camera the less noise will be seen.
The Image on the left has more amplifier noise than the image on the right.
Day/night cameras can operate in greater range of light levels. When it gets dark the camera automatically removes the IR filter allowing more light to hit the sensor. At night the camera also changes to monochrome mode and improves the total light sensitivity of the system.
Cameras from IQinvision and Axis have good low light performance. For example the Axis P3343 and the IQeye IQ752 can operate in light levels as low as 0.05 lux. This means the cameras can see things even our eyes can’t see.
The dynamic range of a camera is a measure of the minimum and maximum light the camera can see in one frame. Wide dynamic range is helpful when you are looking at a person against a very bright background. Sony has introduced cameras with very wide dynamic range that allows you to see the image on the top.
As you can see it’s important to consider many of the camera specifications before selecting a camera. This assures you get the right camera at the right price. The type of lens, iris opening, resolution, compression, and dynamic range all need to be considered.
If you need help selecting the camera or lens, please give us a call at 914-944-3425 or send us a message. We are always there to help you get the right IP camera system.