Some ideas to consider before buying or installing a security system.


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Dec 10, 2014
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Before buying a security system the first thing you need to figure out how is many cameras of what resolution you need to capture what could happen. Be sure to look at the camera specifications. Some cameras are made that do not work in the extreme cold that winter brings to those of us up north. If the temperature is -20f while you are being robbed but your cameras stop working at -4f your cameras are unlikely to record that robbery. One security camera company offers 2 different 1080p resolution security camera systems that record down to -4f or -22f. That temperature represents a huge difference! If you buy the wrong system the cameras may not work when most needed during your cold weather. Just because one system would record in that same cold do not assume all of their cameras will work in extreme cold as a companies cameras can have very different temperature specifications.

To know how many cameras you need you first need to determine how much useful coverage a camera will give you. The USEFUL coverage area changes greatly depending on the sensor used and the lens used. A 720p camera is unlikely to capture any usable footage from 15 feet away. Even a 4k camera is very limited regarding what level of useful detail it can capture at a distance.

If you are recording an alley turn your camera lens sideways. Since we are working with a 16:9 format a sideways camera will capture more image in a narrow corridor with a 9:16 format.

By using this site you can see a satellite image of your house. Then you can add up to 4 generic cameras or manufacturer specific cameras (if you are looking at a certain brand). If your particular camera is not listed email the website. They should have that camera added to the list in a day or 2. You can save a picture of 4 cameras by your house and then move everything to get 4 more cameras in different positions. You can combine the pictures for your overall coverage. You could also pay them $99 for 3 months of use to place unlimited numbers of cameras around your house.

Theiatech's image resolution simulator and lens calculator

By moving your cameras around your property using this calculator you can determine where to actually place your cameras for the best coverage possible.

Below is an example of overlapping coverage. The red lines show how far the IR can see which is usually beyond the effective image capture limits. The red lines point back to where the camera is located. The blue shows what a 90 degree camera will capture. The dark blue shows overlapping coverage which is desirable.

In this 4 camera mock up you can see how 3 of the cameras cover each other. If anyone attempts to damage any camera another camera will capture the event.
The fourth camera would also be covered by another camera when more cameras are added to the other side of the building (the black outline).

The white triangle next to the camera is the blind spot where coverage will not happen. Always keep this blind spot in mind. Activate the blind spot option when using the online camera placement calculator.


You probably did not notice the flaw in the above diagram. The camera that is second from the bottom should be pointed the other direction. That direction is perfect when that camera is moved to the left side of the house with a camera facing it so you would have overlapping coverage.

A quick look tells us we will have excellent coverage but will we really get it? We must consider image sensor quality and the lens chosen. The example above assumes the cameras have a 90 degree lens. We have not yet included PPF (pixels per foot) calculations to determine if images of faces and license plates will be legally usable. In reality with a 4k camera and 90 degree lens we will not get this much useful coverage.

What is PPF and why is it important? Pixels per foot determines the clarity and therefore the legally usable images you can record.

The image below depicts the kinds of Pixelization. A better way of defining the Image Detail is by Pixel Density on a target (pixels per foot or pixels per meter

Digital Video Quality Handbook 2013 by the Dept. of Homeland Security.

Selecting the Right Resolution and Lens for the IP Camera System

As you can see in the pictures above, 40 pixels across the face is probably the minimum number of pixels necessary to recognize a person that you know. If a face is 6.0 inches wide, then we need 80 pixels per foot. (Outdated but still useful information from Cisco)
Video Surveillance Design Guide

As shown in Figure 4-4, the video surveillance image is subject to uneven lighting, the subject is standing near a large window of a lab environment. There is little light from the internal space with the natural light entering from the side and rear in this scene. This image is from an analog camera that does not include a wide-dynamic range processing that would improve the image quality in this deployment. This illustrates the point that the number of pixels alone does not guarantee a high quality image. <-- PPI Calculator (Pixels Per Inch) Additional math can make it pixels per foot.

The perpetrator looks like this officer. The officer replies "I can probably rule out the blondes. You need a better security system"

One of the most challenging aspects of designing modern video surveillance systems involves managing the Owner’s expectations. While most realize that the sitcom and movie makers take some creative license and exaggerate the realities, daily exposure to this media creates unrealistic expectations.

This site offers some great information such as the 2 charts below.

  1. Detecting: image detail of 10 pixels per foot (33 pixels per meter) required (color coded light blue).
  2. Monitoring: image detail of 20 pixels per foot (66 pixels per meter) required (color coded light green).
  3. Recognizing (a known person): image detail of 45 pixels per foot (148 pixels per meter) required (color coded light yellow).
  4. Identifying (an unknown person): image detail of 50 to 60 pixels per foot (165 to 197 pixels per meter) required (color coded light red).

Here is an example of 40ppf the minimum quality image that you want to capture and 80ppf which offers much better quality images. The square box house is the same size. The camera has not been modified in any way. The distance to the object being recorded to obtain a higher PPF image for clarity is the only thing that has changed, The coverage you can obtain is drastically reduced when you require higher quality images. This shows why you might need more cameras than you originally thought.


Is the image quality improvement worth getting? It sure looks like a good idea although finances can impact the decision making. Everything we choose is a compromise.
Notice the dramatic improvement in image quality when the subject is closer.
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Frames Per Second

The more frames a second the better your chances are of obtaining one useful frame. That is why 60fps dashcams are so well regarded. However, in a house that is sitting still do we need such detail? While more information is always better higher FPS comes with a price. In life we make compromises. You may decide that spending 4 times more $$$ to get 30fps or higher is worth it. You may decide that going more than 6 or 15 fps costs to much. Finances compared to actual needs always dictate our final choices.

This company says that 1080p security systems are good enough. I therefore take this information with a grain of salt but i do accept that for slower human movements it should apply.
The higher the frame rate, the more smooth the video footage will be and conversely the lower the frame rate the more jerky the footage will be. 30 fps is normally used for movies. Security cameras won’t be used to film the next Oscar winning production and the recommendation is to record at no more than 6 frames per second

A common misconception about frame rates is that when you compare the recommended 6 frames per second with 30 it sounds like a tiny number and there is a worry that something will be missed by the recorder. This is not the case. 6 frames per second is still a lot of images that are recorded onto your hard drive – every second 6 images are recorded, or one every 170 milliseconds. This doesn’t mean a lot to most people so to put this into context, the average person takes between 300 and 400 milliseconds (1/3rd of a second) to blink their eyes. In the case of footage stored at 6 frames per second, during the time you take to blink your eyes, the recorder has stored 2 or even 3 individual frames. Almost impossible to miss something important

I moved this specification to this section because these days frame rates are not critical in most applications. Most megapixel cameras support reasonably good frame rates. What is reasonable? Well, it depends on the application. In the old days, people said you needed at least 30 fps. That, of course, is not true in most applications. The video is very smooth even at 10 fps. Take a look at our video “How the Video camera Works” for more details about frame rates and how they have evolved from the old days of TV. Yes, there are a few applications where you want higher frame rate, such as in gambling casinos, or in special testing situations, where you need to see very fast motion, but in most cases, you can save bandwidth and storage by reducing the frame rate.

Audio capability can be very important in some applications. For example, if you would like to connect an intercom to the camera you will need two-way audio. You also will require audio in applications like police interrogation rooms. In this case, you need a camera with audio input capability. You can also select a camera with a built-in microphone, but be careful because it’s always best to have the microphone close to the person talking.


Do you want audio? Do you need it? There are 2 options available for those who want to record audio.
  1. Buy a NVR (More expensive than a DVR) as many NVR cameras have microphones built in.
  2. Buy a DVR (Cheaper than a NVR) then add additional cost microphones and (very long) RCA cables. You can find BNC cables with built in RCA wires. The unanswered question is how good is the quality of these cables when used for better than 1080p quality video. Plan on spending an extra $15 per microphone. You might spend more or less than this.
Not all DVR's will record audio. Those that do record audio may only have 1 audio jack built in. Others may have 2, 4, or more audio jacks built in. Look at a picture of the back of a DVR to see how many RCA jacks it has BEFORE you buy it. No, you can not add more audio jacks or use an audio splitter with your DVR.

Hard drive.

The bigger the hd the more that can be recorded before being overwritten (just like a dashcam). The bigger the hard driver the better. Do you want a system that includes a hd or do you want to add your own? If you add your own HD use one designed for security cameras. They do not cost much more and should last a lot longer.

Megapixel differences
CCTV Camera 2, 5 and 8 Megapixel (4K) comparison


Anything that works wirelessly can have connectivity problems. Each has benefits and drawbacks. Ethernet cables as used by a NVR are more expensive compared to siamese BNC cables used by a DVR.

Either a NVR or a DVR could be designed to upload individual pictures or video to the cloud. Either one might not do so at least until you activate the option (if available).

A NVR by definition has wifi included. A DVR probably does not. That means you will have to use a USB cable or buy a wireless bridge to connect to your wifi enabled router.

What brands should you buy? Many experts would say the brands carried by the cheap box stores are all junk. Then again, they are trying to sell you much more expensive options. In the end I can only say to look at the specifications and reviews then make up your own mind.

Is a security system worth anything when you lose electricity? You might consider adding a UPS as additional protection during those pesky power outages. As with everything size matters. As with everything the bigger a UPS is the more it costs. The back up batteries in a UPS do not last forever. I had to change the battery in my computers UPS after 8 years.
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