Shopping For Security Cameras

Dome Cameras

QUESTION From David in Allentown, PA:

I'm looking into a security system for a bar I'll be opening in the spring. Any suggestions, horror stories, recommendations, tips on what systems have worked well for you guys?

David P.  Allentown, PA



Like any service - be sure to select one that doesn't lock you in (have a trial period to make sure equipment is what you expected even if it's a no money back deal but you're not penalized for upgrading or downgrading equipment). Secondly, make sure they'll be there on the fly to fix or maintenance the equipment in the event of a problem.

Most systems these days have remote viewing app associated with the system, the option to include audio recording and a lot of the other bells and whistles.

Because of that I’ll focus on what I and several of my colleagues consider the most important thing: Image Quality

The most common choices when it comes to cameras are shotgun style cameras for distance and dome cameras for greater field of (closer) view.

Although many cameras are capable of filming in 1080 or HD, Recording and playing back at that same quality is a whole different story.

When I was shopping for security system I was surprised to discover how many cameras that record in HD were being sold with hard drives / storage devices that were not capable of playing the recording back at the same HD quality displayed on the screen during live view unless you only used 1 or 2 cameras...or intended to record only 4-6hrs with each camera before the hard drive was erased and written over.

The reason for this - simply put- is that video recordings take up bandwidth known as a “bit rate” and the storage device needs to be capable of storing and playing back what each camera records. If the storage device does not accommodate the bit rate of the camera… Where the total combined bit rate of all the cameras- Then image quality is compromised.

I’ll give you an example with very round and arbitrary numbers:

Let’s say one camera can record five days in HD quality at 15 frames per second and at camera recording takes up a bit rate of 5Mb/s.

If you have 4 of those cameras and want to have a storage device capable of holding and playing back the video at the same HD quality- the hard drive would need to be rated for 20Mb/s.

As I said these numbers are completely arbitrary but it may give you an idea what I’m talking about. Most folks at Costco, Best Buy and ADT know very little if anything about bit rates...and the rating is sometimes hard to find on some devices.

You may not find the same quality in the value packages you find at most home-improvement stores.

A commercial security company can provide better equipment if you communicate your basic needs and wants (e.g., price, number of cameras / zones and constant or motion activated recording) - just be sure to mention that you want the hard drive (or cloud based storage- which is impossible to steal in the event of a break-in/robbery) capable of recording in playing back the same high-quality you observe on your screens and be sure they are rated for a bitrate that exceeds your current needs in the event you want/need to add a camera or two... which is often the case.

Swan Communications has a page that discusses this all in greater detail and provides the following equation for you or your tech-support to do the math and ensure you have the right equipment.

Here’s a link to a helpful thread that really gets into detail:

Here's the part about bit rates and how to calculate capacity if you're so inclined:

What is the recording capacity of your system?

While technically Mb/s (Megabits per second or bit rate) can also be used as a measure of storage used over time, it’s not very useful to us when making calculations.  While the marketing material will provide for X days of recording, a general ‘days’ figure may not address your recorder’s usage pattern.  To be precise, you will need to make your own calculations.


Firstly, we need to convert the bit rate into a more usable unit.  For this, we select MB/h (Megabytes per hour).  This is best suited for determining how many hours of recording our storage solution will hold and can then be used for calculation of days of recording taking into account various other factors.


Let’s look at the formula for this calculation:


MB/h = Mb/s x 60 x 60 ÷ 8


Firstly, we have to multiply by 60 twice to convert from seconds to hours, then divide by 8 to convert from bits to bytes.  We can consolidate that formula, and if we do so:


MB/h = Mb/s x 450


Therefore, we can see that by strict calculation, each 1Mb/s will equal 450MB/h.  In practice, with compression and variable bit rate encoding, the figure is closer to 400MB/h but 450Mb/h is a perfectly usable and easy figure to remember.


Now, we take that figure and multiply our camera bit rate to get the usage of one camera for an hour.  We’ll use a popular example, the default bit rate for the NHD-815 3-megapixel camera:


Camera storage utilisation (MB/h) = 5(Mb/s) x 450(MB/h)


This works out at 2250MB/h or just under 2.2GB/h.  HD cameras use a lot of space!


NB: To convert from MB/h to GB/h, you divide by 1024, not 1000.


Once we have a figure for the amount of space used by a camera per hour, we can then divide our total storage by that figure to arrive at a figure for Camera Hours.  Quite simply, the amount of hours of recording for one camera that will fit on the installed storage.  Once you have that then you can adapt the figure to any number of cameras and time requirements.


Example: A standard 1TB HDD, after formatting and file system overhead, has approximately 920GB space available.  Dividing 2.2GB into that yields a figure of 418 camera hours.”

Josh SapienzaComment