All you need to know before buying a security camera


All IP Camera manufacturers provide product specification sheets that claim to help you select the right camera for your IP security and surveillance system.

However, this information can be confusing to most people. How do you know which specifications are important? How can you hope to choose the right security camera if you don’t really understand or appreciate the importance of resolution, minimum light sensitivity, the workings of lenses and irises and how the angle of view can affect the usefulness of your captured video footage?

Well, hopefully the following information might help you to understand these issues a little better and ultimately help you make the right choice when you finally get around to buying your security camera.

Choosing security cameras

When it comes to choosing which type of security camera to install, whether hard-wired or wireless, the choices will ultimately be determined by your individual requirements, your budget, the layout and location of your home and what you want to achieve with the home security system. The relative importance of each of the camera specifications discussed below depends on your objective and application for your IP camera system.  If you intend to use the camera outdoors where it can get dark, for example, then the low light specification will be important. If you are only using the IP camera indoors, you may be more interested in the how wide a viewing angle you can achieve.

Wired or wireless CCTV – which is the best fit for you?

Wired security cameras

Wired home CCTV systems are the most commonly used type of camera and, therefore, the cheapest. The connection between the camera and the monitor is achieved using a direct wiring link. The advantage of hardwiring is that signal will generally be consistent and will only fail if there is a power outage or failure at the property. However, the downside to hardwired cameras, as well as their extension cables and connectors, is that they can be difficult to install, so a technician’s expertise might be required, making the initial outlay expensive. The upside, on the other hand, is that once installed their functionality and performance is every bit as good and reliable as their wireless alternatives. Where wired security cameras really struggle is in terms of flexibility. Once a wired camera is set up and connected, it’s a complicated procedure to move it to another location.

The good news is that things are changing as technology evolves. Many security companies have now adopted PoE technology and are manufacturing PoE-enabled wired security cameras. What this means is that these wired cameras are much easier to install than older analogue cameras, and it also means that moving them shouldn’t be as complicated or convoluted should you later change your mind about the camera’s positioning. If you would prefer to choose a wired security camera, are considering self-installation and are concerned about flexibility, then the right choice for you would be a DIY PoE IP security camera.

Wired security camera advantages

  • Wired security systems can often accommodate several ‘zones’ of protection.
  • Wired systems are reliable.
  • Wired systems generally tend to be less susceptible to radio or electrical interference.
  • Wired systems use a backup battery system during electrical interruptions.

Wireless security cameras

With a wireless home CCTV system, cameras transmit images to a computer, tablet or mobile phone, using either analogue or digital technology. Many smart security cameras can even link to an app that you can use to monitor your home whilst you’re elsewhere. Digital cameras are generally higher quality and produce better images than their analogue counterparts, but they are consequently that much more expensive.

Wireless security camera frequencies

The communication between camera and receiver takes place at a frequency specific to both devices. Most wireless devices, cameras in this case, allow you to select from only four frequencies. Frequency limitations usually limit you to four cameras per location at a given frequency

How are wireless security cameras powered?

Although the video signal that transfers the signal from the camera to the receiver and monitor might be wireless, sadly a totally wireless security camera set up is still not yet available. Therefore, each of the devices – the camera, receiver and monitor- still need a power source. So, security cameras need to be set up near electrical outlets.

What benefits can you expect from wireless security cameras?

Easy to install
  • Wireless security cameras are much easier to install than their wired alternative. The latter needs to connect to a home’s electrical system. If you would prefer a wire home security system, then you’ll probably have to hire a professional to install it. Wireless cameras, however, rely on Wi-Fi or other networks so they’re much easier to install. If you follow the installation instructions carefully, there’s no reason why you can’t set up and connect most cameras in under 30 minutes.
Portability and flexibility
  • Wireless security cameras are flexible pieces of kit and can by and large be placed almost anywhere. They’re also portable and transportable: all you need to do is unplug them, and you’re ready to go. That makes them ideal for people who are either renting or always on the move, or those who are novices and new to the home security scene.
24/7 coverage
  • Wireless security cameras are a great addition to your home security system, as they offer you 24/7 viewing access to your home, no matter where in the world you are.
Wireless issues

Wireless systems are not without their faults, however. They can be plagued by interference from devices like routers, cordless phones and microwaves, and can potentially be blocked and have their signal impeded by heavy masonry or metal objects. The ability to record and transmit film is also dependent on signal quality and consistency: so, filming might be interrupted if an internet connection is lost. What’s more, wireless home CCTV systems will need to be encrypted, to prevent anyone within range with access to a suitable receiver viewing the homeowner’s images.

What types of security cameras are available

Box Cameras

These are the most commonly used video surveillance tools. They’re cost effective, they’re a visible deterrent and they make sense for most security applications. What’s more, many box cams can accept a variety of interchangeable lenses that let you adjust their viewing angle to optimise coverage of the area you need to monitor.

Dome cameras

Dome cameras are also a common and popular security choice. Dome cameras are generally much less obtrusive than box cams – depending on their size – and they’re easy to mount in most locations. Interchangeable dome cam lenses are available at the more expensive end of the spectrum.

Pan/tilt/zoom cameras

PTZ cameras, by their nature, offer more installation and monitoring options. They can swivel up and down and side to side, so you can cover a full 360-degree field of view with only one camera. The vast majority of PTZ cams are remote-controllable, which makes them a great choice in many single-camera surveillance setup

Bullet cameras

Bullet cameras are similar to traditional box cameras. They serve as a visible deterrent and they come in a variety of sizes — some are very large; others are extremely compact. For monitoring flexibility, many bullet models come with variable focal length zoom lenses, whilst some also offer an interchangeable lens option.

Lenses, resolution and angles of view

What is lens resolution and why does it matter?

When you hear the word resolution, what we’re talking about is the quality of the image. As the resolution increases, the image becomes clearer, and by that we mean it becomes sharper, crisper, more defined and more detailed. The reason for that is that there’s more information contained in the same small space. Computers, laptops and smartphones all have image resolutions. There are a certain number of dots/ pixels contained in the screen space, and the more dots you are able to fit into the width and height of the screen, the higher the resolution: and by contrast the fewer dots you pack into the space the lower the resolution will be.

As technology has advanced so has the ability of computers, laptops and cameras to resolve images. Resolution is no longer measured in lines as it was back in the day: today resolution is measured by the total number of pixels in the sensor or the horizontal and vertical pixels.  You’ll frequently see the terms HD, 720p or 1080p, and most recently 4K used: but in truth, it’s all very confusing and very few people know what these terms mean. Hopefully, the following might help.

Megapixel camera

This is a general term used for any camera that has over 1 million pixels in the sensor. There are many cameras that have over 1-megapixel resolution.  For example, there are 2.0, 3.0, 5, 8, 10 and higher megapixel cameras. The pixels are organized in a matrix of horizontal and vertical pixels.  The relationship between the horizontal and vertical pixels is called the aspect ratio.   The aspect ratio (vertical to horizontal ratio) is usually 4:3 or 9:16 (wide).  For example, a 1.2 Megapixel sensor on the Sony SNC-EM600 camera has 1280 horizontal pixels and 1024 vertical pixels.  The aspect ratio is 1280/1024 which is 1.24 or close to the 4/3 ratio (1.3).  The 2-megapixel Samsung SND-6084 dome camera has 1920 x 1080 pixels, and the aspect ratio is closer to 16:9.  The latest sensors (especially the ones that claim 4K resolution) have different aspect ratios that are similar to the very wide formats used in the cinema market.

HD camera

Many security cameras are marketed as either 720p or 1080p type HD cameras.  This specification comes from the video broadcast market rather than the security market. Historically TV had only 525 horizontal scan lines per frame: the 525 figure wasn’t the actual resolution, but rather the physical scans of an electron beam on a CRT (Cathode Ray Tube). The total number of horizontal lines in a frame was made up of two fields (262.5 lines per field). The fields were then interlaced, so viewers wouldn’t see the flicker.

Nowadays 720p refers to 720 pixels in the vertical direction. The “p” indicates “progressive” rather than “interlaced.” The older TVs used two interlaced fields to make one frame. Each field had half the number of lines. Today the cameras and displays (monitors and TVs) have a single progressive frame that includes all the lines (pixels) at one time.  The 1080p HD camera has at least 1080 vertical pixels (or horizontal lines).

720p cameras usually have a sensor with at least 1.0 megapixels. Pixel resolution is 1280 x 1024 (like the Sony SNC-EM600 1.3-megapixel camera), or it can be 1280 x 800 (like the Axis M3004 1.0-megapixel camera).

1080p cameras have at least a 2-megapixel sensor, and it is considered to be the higher resolution “HD camera”.  To confuse us, some manufacturers specify their 3-megapixel or 5-megapixel camera as “1080P” as well. Is it any wonder there is such confusion in the area?

4K camera

This usually refers to a camera with over 8 Megapixels of resolution.  It has approximately 4,000 horizontal pixels. There is some difference between the definitions of the television industry and the security market.  The number of vertical and horizontal pixels and the aspect ratio are defined differently. For example, Axis introduced a camera with 3840 x 2160 which runs at up to 30 fps (which they called Ultra HD).  The Sony 4K IP camera has a chip with 4096 H × 2160 V pixels which run at up to 60 fps and conforms to the Digital Cinema Initiative. The Hanwha (Samsung) PNO-9080R has a resolution of 4000 x 3000 pixels.  All of these cameras are referred to by manufacturers as 4K.

Other resolution issues

The resolution of a camera is determined not only by the sensor, but also the lighting, lens and the electronic circuits. Generally, you should be careful when you purchase a camera and not set too much store by the claims made by some manufacturers. A camera can claim to be a megapixel IP camera, but you generally get what you pay for. So, if the price is low, you can generally expect substandard performance.  The sensor may have the megapixels, but the lens may be plastic, and the result is a very low-quality image.

Minimum illumination (low light sensitivity)

The minimum illumination is the lowest light level that provides a reasonable image from the IP camera. It is measured in lux.  This can be very subjective.  It depends on what you think is an acceptable image.  At the low light level, the amplifiers are working very hard and there can be circuit noise that affects the video image.  This is called the signal to noise (S/N) ratio.  The better manufacturers also include the relative level of the signal (IRE), which is a measure of how hard the amplifier has to work.  For example, a camera that is operating at 30 IRE is receiving 30 per cent of the signal from the sensor circuits, while one operating at 50 IRE is receiving 50 per cent of the signal.  The lower the IRE number, the harder the amplifier has to work to boost the signal so it can be seen.  The noise level can be as high as 20 per cent of the signal so the resulting video can look very noisy when the signal level is very low.

The minimum light level is also affected by the shutter speed, which relates to the frame rate.  The longer the shutter is opened the more light can reach the sensor. The longer the shutter stays open, the lower the frame rate. There are some camera specs that indicate very low minimum illumination (0.0001 lux), but this is measured at a shutter speed of 0.5 sec.  This translates to a maximum frame rate of 2 fps. The minimum illumination level is also determined by the lens.  The lower the f-number of the lens the more light it will let through.

Lens

Many IP cameras come with a lens.  The lens allows you to frame the area that you want to see.  For example, a wide-angle lens could be used to view a small room, while a narrow-angle lens (with more magnification) can be used to see an area that’s far away.  The lens also can affect some of the other specifications such as minimum illumination, frame rate, and resolution.  If the IP camera doesn’t include a lens, it usually includes a standard type CS (or C) mounting capability, so you can use various third-party lenses.

The lens angle is measured in millimetres (mm).  The lower the number the wider the viewing angle. A 2 mm lens may have an angle of about 110 degrees, while a 50 mm lens has an angle of about 5.5 degrees.   The angle of the lens depends, as mentioned earlier, on the size of the sensor and the distance from the sensor to the lens.  Many manufacturers make it easy and provide both the mm and the angle of the lens in the specification. Once you know the distance and field of view, you can select the right lens.

The f-number of the lens indicates how well the light is transferred through the lens.  A camera with an f-number of f1.2 can pass more light than one that has f2.0 lens.  The f-number will also appear as part of the minimum illumination spec.  The lens angle can affect the f-number, the wider the angle the more light can get in, so the illumination spec is usually measured at the widest lens angle (when a variable lens is included).

The anatomy of lenses

There are several types of lenses available for security cameras: fixed lenses, variable, and zoom lenses. Fixed lenses have only one mm setting, variable lenses can be manually adjusted through a range of angles and zoom lenses carry out the same function as variable lenses but are able to do this remotely.

Irises

There are manual iris controls, DC auto iris, and p-iris lenses. The iris affects the depth of field.  Iris control adjusts how much light falls on the sensor.   The smaller the iris opening the longer the depth of field. When the scene is very dark the lens iris opens, and the field of view is reduced.  This means some areas that are close or far away are not in focus.

The manual iris is manually adjusted and depends on how much light is expected in the scene. A manual iris lens is usually used with indoor cameras where there is a small light variation.

The DC auto Iris lens is usually used with outdoor cameras.  The camera electronics adjust the iris opening depending on how much light it detects. At night it opens the iris and when there is bright sunlight it closes the iris.

P-Iris lenses are similar to the DC auto iris lens, except they add additional intelligence to the lens opening.  When the iris is closed all the way, it can reduce the clarity of the image (when used with megapixel cameras).  It has to do with the pixel size.  A P-iris camera system works with the camera electronics to prevent the iris from closing all the way.  On the other hand, when the view is very dark, the camera tries to open the iris to let in as much light as possible.  As the iris increases the depth of field is reduced.  The p-iris lens prevents the lens from opening all the way and compensates by increasing the camera amplification of the video signal.

IR lenses

Lenses bend the light to achieve the right focus and magnification.  Infrared (IR) light can bend at a different angle than visible light when the wrong type of glass is used in the lens.  IR corrected lenses compensate for the focal difference and provide a much clearer image.  This is most apparent at the higher resolution.  If you plan to use a megapixel IP camera system, then make sure you get the IR type lens.

Focus

The focus of the IP camera can be adjusted either by manually adjusting the lens or by remotely adjusting the distance between the lens and the sensor (back focus).  Lenses can have a fixed focus (that can’t be changed), manual focus or auto-focus.  “Back focus” is not part of the lens but is usually listed with the lens specification.  This is a great feature that makes installation much easier.  The focus can be adjusted at the computer, instead of at the camera. Many of the new Sony and Samsung cameras have this feature.

Wide dynamic range (WDR)

When you’re trying to view an area with challenging lighting conditions it’s best to select a security camera that provides a good wide dynamic range (WDR).  For example, when you view a lobby with a large window, you will need a camera that either provides backlight control or, better yet, WDR.  The wide dynamic range has been dramatically improved in the latest cameras.   WDR is measured in dB.  The older cameras provided about 50 dB of WDR, but that figure has increased dramatically over the last few years. Many camera manufacturers now offer cameras with WDR of over 100 dB, whilst the latest Sony and Samsung cameras now provide over 120 dB.  In many cases you don’t have to pay more for this capability, all you need to do is choose wisely and select the right camera.

Security camera coverage

Angles of coverage

For CCTV camera and IP camera, the term ‘angle of coverage’ describes the angle range that a CCTV camera lens can image. Typically, the video image circle produced by a lens will be big enough to cover the CCTV camera image sensor completely. If the angle of coverage of the lens does not completely fill the image sensor, the image circle will be obvious: it will typically show signs of strong vignetting toward the edge of the image and the effective angle of view will be limited to the angle of coverage.

Is there any such thing as an average security camera angle?

The simple answer to that question is no. There isn’t an average security camera angle, as it is largely determined by the design of camera, the technology the camera employs, the focal length of the lens and the size of the image sensor.

For CCTV camera and IP cameras, the Angle of Coverage is predominantly determined by both the focal length of lens and the size of image sensor. Generally speaking, the larger the image sensor, the wider the angle of coverage will be; and the higher the focal length of the lens, the narrower the angle of coverage will be. However, it also needs to be remembered that different image resolutions can also affect the angle of coverage.

Usually, the size of CCTV camera image sensors ranges between 1/3″ to 1/2.5″; and the focal length of the lens will range from 2.8mm to 12mm and everything in between depending on the type and make of the CCTV camera. With 1/3″ of image sensor, 2.8mm focal length will deliver an angle of coverage of around 90°: a 4mm focal length will deliver around 70° coverage, 6mm around 43.3°coverage and a 12mm focal length twill deliver around a 20.6° angle of coverage

Modern security CCTV cameras can cover diagonal angles ranging from 60 to 170 degrees, with most ranging between120–130° on ‘average’, and few, if any, covering an angle of less than 90°. It should also be pointed out that the angle of coverage of CCTV cameras will be also be dependent on both the type of camera used and the technology employed by the camera.

  • Box and Bullet security cameras: typically cover an angle ranging from around 80 to 100 degrees
  • Dome security cameras: typically cover an angle of around 100 degrees
  • PTZ security cameras: typically cover an angle of roughly 360 degrees with no blind spot.

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