[We're still in the cameras part of our Designing Hardware for HD series. Be sure to check it out!]
[This time, I've asked Fabrizio Ghetti, Video System Engineer in our Italian R&D center, to provide a short list of requirements to look for when shopping around for endpoint cameras.]
When you go out to shop for a camera for your hardware endpoint design, you will be looking at a lot of brochures showing different specifications. Even if the camera may seem perfect on paper, you should personally check it on your own – make sure it works well in the environment and use-cases your end product will be operating in. Keep in mind that besides great specifications, there are some algorithms that run in the camera that can change its results and performance when used in your settings.
Before I will provide here the list of characteristics I use when selecting cameras, I’d like to note that a camera’s performance is a complex combination of resolution, lens, colors, noise, and algorithms. These will be different between camera brands, so shop wisely.
The more resolution your CCD/CMOS has, the more details you will be able to capture in the image. This in effect will increase the depth of field and by that the 3D feeling of the video stream.
You should note that higher is not always better though, as it does come with a price – more resolution means more data for the camera to process, which means more complex circuitry, usually making the end result more expensive.
Maximum Resolution of the Video Signal
Got a camera? Make sure it has the right output signal to fit your hardware design – especially the video processing chip which will be doing the encoding.
Keep in mind that you might want to have a camera with resolutions higher than what you are capable of processing today – just to be able to upgrade the system in the future without replacing it, as camera selection takes time and resources. This is why for a system that can handle 720p at 60 frames per second you might want a camera that can handle 1080p resolutions as well.
Horizontal Field of View (FOV)
Keeping it simple, horizontal field of view is the viewing angle the camera will provide. The larger the viewing angle the more you will see of the room you are capturing with the camera. This translates to the amount of people that will be visible at once during a meeting.
A reasonable value for horizontal field of view for a room system is 70° or more. For a personal video system a good angle could be 60° or more.
Video conferencing might require the ability to zoom in and out. This is especially true in a conference room setting, when you might want to zoom in on the speaker, or because there’s something you actually want to show or explain and the details become important. For that, you will need some zooming ability in the camera.
Optical zoom is the standard for most room systems today. It ensures that the details shown when zooming in have as little noise as possible. My advice? If possible, always choose optical zoom if you can.
A good zoom ratio for a video conference room is 10x optical zoom.
When you use personal video systems, you usually won’t have optical zoom capabilities, as they increase the cost of the system. In such cases, you might resort to digital zoom, but not always.
When digital zoom is available, then 2x zoom ratio is usually sufficient.
Lens Quality (Distortion)
The lens inside the camera can greatly affect the image quality. One such aspect is the distortion it might introduce. When lenses are developed for a given camera, then moving it to another camera design it might not provide the best image quality – it can cause distortions.
Here’s what this might look like:
Camera lens distortion
Make sure the camera doesn’t distort the image.
There are different aspects related to the room settings in which your product will be deployed. Here are a few of them to keep in mind:
In some countries, powder/dust can be a big problem. If you don’t have a lens protection, then you’ll have to clean the lens before doing a video conference. Some kind of protection for the lens against dust can make sense in these cases.
Sensitivity to Illumination Conditions
At times, you will need a solution that works in low illumination conditions. Make sure to test your camera for low illumination if you expect it to work in such a scenario.
If there’s any backlight, coming from a building window or some other source of light, check if the camera of your choice is capable of compensating for it. Make sure you do the test yourself, as almost any camera vendor has some kind of a solution for it in his camera, but the differences between cameras can be significant.
Pan Tilt Requirements
If you’re going for a PTZ camera, there are a few additional characteristics that you’ll need to consider:
- Pan and tilt angles that it provides
- Motor speed, to change quickly between different modes
- Interface it provides to control the camera’s motion (serial, infrared, etc)
- Number of possible preset positions
- Number of cameras that can be controlled by a single serial interface if they are connected to each other
As every technical aspect, in the cameras market, different brands are known for different qualities: one brand is best known for its lens quality and low distortion, another brand is known for its color reproduction, while another for its reliability and assistance.
Other things to check
The list is longer than that – signal to noise ratio, frame rate and other aspects are other things you will need to check.
Bottom line – selecting a camera is a kind of an art…