Last run, I told you that we would get into what it takes to put the cameras together and here we are. This is the best (in my opinion) flow of system design. In the last column we went for the system purpose. This time, we deal with the camera purpose and the requirements of choosing a good IP or analog camera. I will, as always emphasize that the process of design with IP runs a very tight parallel with analog systems. This means that those of you that are dreaming of IP design, but still working with analog can benefit from this portion as well.
The first step to choosing a proper camera -- be it IP or analog -- is to choose the location as based upon the application. You must first determine what you are trying to see and why. Then you must write it down. Yes, I know, you plan to have 300 cameras. All the more reason that you take good notes. Each camera will have its own sheet. Each sheet will ultimately end up with everything on it that you need to produce an image equal to your application. When you are done, your system will work right the first time and it will be tight.
Let's say that you plan to cover a lobby entrance. The application calls for a camera to be mounted in such a way as to view traffic into and out of the facility. It would also dictate that you come up with identifiable images on the playback of your recorded image. Therefore, you have the purpose, and now you must match the location to the challenge. Don't worry about what lens to use or how close or far the camera will be. Not yet. First look at the options. If you mount the camera over the door, will you see faces or tops of heads? If you mount it on the adjacent wall, will you be looking into bright light? If you put it outside, will it be exposed to weather or rough treatment? All this to think about, but sooner or later you will come down to two or three possibilities. You must, however remain realistic. You cannot mount a camera in mid air. You cannot mount a camera to a moving object. You cannot mount a camera to a wall or post or whatever if it is known to vibrate. Well you can, but I wouldn't recommend it, so stay realistic. In some cases, you may want to pick a potential second point for installation just in case you need to relocate. In most cases you will be OK with your first choice.
Lenses and Lighting
Now, take notes about your location of choice. The first part will insure that you pick the proper lens when the time comes. The second bit will insure that the group you hire to install the job will be ready and able to go to work.
The first bit will determine the lens that you require for this job. You will need to know three things. 1) the height that you plan to mount the camera. 2) the width of the scene that you plan to end up with. 3) The distance of the camera from the mounting point to a center point of the scene.
Once you determine the height that you plan to mount the camera, you will need to calculate the distance from the camera to the middle of your scene. The middle of the scene will be based upon the width at any point along the axis of the view. That is to say, I want the view to be 12 feet wide (4 meters +/-) and 15 feet from the camera. Or, 25 feet wide at 30 feet from the camera. Take more notes. Look at the area you want the camera to be mounted to and note the material that it is made of. Note if there is a bright background. Look for obstructions, and not just the obvious ones, but ones that could in the future become a pain in the image, like fast growing trees or temporary marketing banners. Look to see and note if you will be looking directly into the sunrise or sunset or perhaps electric lighting. Write all of this down. It may not seem important in the beginning, but you are starting to let the application design the lensing and features that you will need.