Sensor Cameras

A digital camera uses an array of millions of tiny light cavities or 'photosites' to record an image. When you press your camera's shutter button and the exposure begins, each of these is uncovered to collect photons and store those as an electrical signal. Once the exposure finishes, the camera closes each of these photosites, and then tries to assess how many photons fell into each cavity by measuring the strength of the electrical signal. The signals are then quantified as digital values, with a precision that is determined by the bit depth. The resulting precision may then be reduced again depending on which file format is being recorded (0 - 255 for an 8-bit JPEG file).

Light Cavities

Some motion sensor cameras are equipped with an ‘infrared eye’. Infrared is a spectrum of light not visible to the naked eye and detects the heat signatures of different objects, animals, and people. Each motion sensor camera will be slightly different in terms of what kinds of movement might trigger the sensor, but, as a general rule. Digital camera sensors explained Every digital camera has at its heart a solid-state device which, like film, captures the light coming in through the lens to form an image. This device is called a sensor. In this article we explain the different sensor types and sizes.

However, the above illustration would only create grayscale images, since these cavities are unable to distinguish how much they have of each color. To capture color images, a filter has to be placed over each cavity that permits only particular colors of light. Virtually all current digital cameras can only capture one of three primary colors in each cavity, and so they discard roughly 2/3 of the incoming light. As a result, the camera has to approximate the other two primary colors in order to have full color at every pixel. The most common type of color filter array is called a 'Bayer array,' shown below.

Photosites with Color Filters
Sensor cameras waterproof

A Bayer array consists of alternating rows of red-green and green-blue filters. Notice how the Bayer array contains twice as many green as red or blue sensors. Each primary color does not receive an equal fraction of the total area because the human eye is more sensitive to green light than both red and blue light. Redundancy with green pixels produces an image which appears less noisy and has finer detail than could be accomplished if each color were treated equally. This also explains why noise in the green channel is much less than for the other two primary colors (see 'Understanding Image Noise' for an example).

Note: Not all digital cameras use a Bayer array, however this is by far the most common setup. For example, the Foveon sensor captures all three colors at each pixel location, whereas other sensors might capture four colors in a similar array: red, green, blue and emerald green.

BAYER DEMOSAICING

Bayer 'demosaicing' is the process of translating this Bayer array of primary colors into a final image which contains full color information at each pixel. How is this possible if the camera is unable to directly measure full color? One way of understanding this is to instead think of each 2x2 array of red, green and blue as a single full color cavity.

This would work fine, however most cameras take additional steps to extract even more image information from this color array. If the camera treated all of the colors in each 2x2 array as having landed in the same place, then it would only be able to achieve half the resolution in both the horizontal and vertical directions. On the other hand, if a camera computed the color using several overlapping 2x2 arrays, then it could achieve a higher resolution than would be possible with a single set of 2x2 arrays. The following combination of overlapping 2x2 arrays could be used to extract more image information.

Note how we did not calculate image information at the very edges of the array, since we assumed the image continued in each direction. If these were actually the edges of the cavity array, then calculations here would be less accurate, since there are no longer pixels on all sides. This is typically negligible though, since information at the very edges of an image can easily be cropped out for cameras with millions of pixels.

Other demosaicing algorithms exist which can extract slightly more resolution, produce images which are less noisy, or adapt to best approximate the image at each location.

Sensor Cameras Waterproof

DEMOSAICING ARTIFACTS

Images with small-scale detail near the resolution limit of the digital sensor can sometimes trick the demosaicing algorithm—producing an unrealistic looking result. The most common artifact is moiré (pronounced 'more-ay'), which may appear as repeating patterns, color artifacts or pixels arranged in an unrealistic maze-like pattern:


Second Photo at 65% of Above Size

Two separate photos are shown above—each at a different magnification. Note the appearance of moiré in all four bottom squares, in addition to the third square of the first photo (subtle). Both maze-like and color artifacts can be seen in the third square of the downsized version. These artifacts depend on both the type of texture and software used to develop the digital camera's RAW file.

However, even with a theoretically perfect sensor that could capture and distinguish all colors at each photosite, moiré and other artifacts could still appear. This is an unavoidable consequence of any system that samples an otherwise continuous signal at discrete intervals or locations. For this reason, virtually every photographic digital sensor incorporates something called an optical low-pass filter (OLPF) or an anti-aliasing (AA) filter. This is typically a thin layer directly in front of the sensor, and works by effectively blurring any potentially problematic details that are finer than the resolution of the sensor.

MICROLENS ARRAYS

You might wonder why the first diagram in this tutorial did not place each cavity directly next to each other. Real-world camera sensors do not actually have photosites which cover the entire surface of the sensor. In fact, they may cover just half the total area in order to accommodate other electronics. Each cavity is shown with little peaks between them to direct the photons to one cavity or the other. Digital cameras contain 'microlenses' above each photosite to enhance their light-gathering ability. These lenses are analogous to funnels which direct photons into the photosite where the photons would have otherwise been unused.

Well-designed microlenses can improve the photon signal at each photosite, and subsequently create images which have less noise for the same exposure time. Camera manufacturers have been able to use improvements in microlens design to reduce or maintain noise in the latest high-resolution cameras, despite having smaller photosites, due to squeezing more megapixels into the same sensor area.

For further reading on digital camera sensors, please visit:
Digital Camera Sensor Sizes: How Do These Influence Photography?

Statista reports that in the US in 2017, over 7.5 million cases of property crime were reported, with the FBI adding that in 2018, this number dropped to around 7.2 million cases. Despite the efforts of our police forces, however, and the fact that numbers have been decreasing year on year since the early 90s, larceny-theft is still a major issue, with around 72% of property crimes being larceny related.

This is why many choose to install home security cameras for added, protection, security, and as evidence to provide to the police or insurance companies should anything happen. Nowadays, motion sensor camera systems are the go-to and are pretty affordable too which is why today we wanted to guide you through choosing and installing a motion sensor camera system.

What are Motion Sensors and How do they Work?

Motion Sensors are triggered by (you guessed it) motion and can be integrated into a variety of home security systems tailored to your specific needs.

Motion-activated lighting is one of the most common to have around the home, not only for security purposes but to stop you from taking a tumble when you step out of the house in the dark. Motion sensor lighting can be especially useful if you have a large garden and live in a rural community.

Cameras

Just like motion sensor lighting, motion sensor camera systems are triggered in the same way and can be used as an efficient security camera system as they’re only triggered by movement, saving both energy costs and virtual storage. In some scenarios, they can even be used in conjunction with motion sensor lighting to deliver a crisp and clearer image.

Finally, one more common use for motion sensor camera systems is for perimeter fences. Designed for those who live on properties situated on a larger area of land, motion sensors around the perimeter of your property can send an alert to you in your home if they’re triggered.

As you can see, motion sensors can be used in a variety of different ways and ensure you can rest easier in a safer and more secure environment.

So, what’s the science behind them? How exactly do they work? To answer this we need to look at the different types of motion sensor cameras.

Types of Motion Sensor Camera Systems

PIR (Passive Infrared) Systems

Some motion sensor cameras are equipped with an ‘infrared eye’. Infrared is a spectrum of light not visible to the naked eye and detects the heat signatures of different objects, animals, and people.

Each motion sensor camera will be slightly different in terms of what kinds of movement might trigger the sensor, but, as a general rule, anything around 25 -35lbs minimum showing some form of movement is a good guideline.

Microwave Occupy Sensor

Some motion sensor cameras can be fitted with microwave technology too, which means that rather than using the infrared waves of light it uses microwave pulses. Microwave Occupy Sensors are said to be an active technology rather than a passive one like we see above. These sensors have a better range but tend to be less common as they’re more expensive and can suffer from electrical interference easily.

Dual Technology Sensor

Finally, you can also get dual technology motion sensors, which are a combination of the two types of motion sensor cameras we mentioned above. The system works the best when both technologies are activated which means fewer chances of false triggers occurring.

Cameras may also offer less common types of technologies such as vibration, gestures, ultrasonic waves and tomographic sensors.

Issues with Motion Detection

When motion detection systems first came out, they were a little too sensitive, meaning the slightest trigger resulted in people getting alerts over something that wasn’t really a security issue. This can still happen today with larger dogs, and, if you live in a wilderness area, large mammals. However, the systems can now easily be tailored and adjusted to different levels of sensitivity; meaning that you’re not inundated with these false alarms.

Aps-c Sensor Cameras

Nowadays, a good smart camera will easily link up to your phone, so you can set it up and give it a trial run so the sensitivity is set to your liking. You can also quickly check the camera should an alert be triggered and can do it from wherever you are.

Another common yet easily resolved issue is not receiving alerts. If you’re away from home or on the other side of your property, you could be unaware that there’s a security risk. The workarounds for this are actually pretty easy and in most cases, it’s down to a technical glitch.

Either the alerts can accidentally turn themselves off or your emails/notifications could be sent to an incorrect email or going to the spam folder. Another, sometimes common reason behind not receiving alerts is that the email address associated with the account may not have been confirmed/verified for security purposes, and this means alerts don’t come through.

If you’re experiencing issues with alerts and have tried the above workarounds, reaching out to the manufacturer would be the next port of call.

How to Choose the Right Motion Sensor Camera

As you can see, there are endless options for motion sensor camera systems, so how do you pick the correct one? It’s all down to each camera’s individual features and how they’ll suit you best. Let’s take a look at some important features to consider.

Range: When installing cameras on the exterior of the property, you want to ensure that they have a good range. In this kind of scenario, investing in a dual system that has the properties of infrared detection with the long-range capabilities of microwave sensors could be a great choice.

Mounts: Does the camera come with mounts? If so, what kind are they? Will they easily fit onto an exterior wall? These are all questions you should ask yourself when looking at potential models.

Sensor Technology: By understanding the different types of motion detector technologies we listed above, you can make a more informed decision about which will be best for your home.

Ease of Installation: No one wants to spend hours installing a system, or go to the effort of paying for someone to come install it, which is why you should always choose something that’s easy to install. Get recommendations from friends and even ask the people working in the store for their opinion. When in doubt, Google it. There is a wealth of reviews on the web and they’re sure to mention the installation procedure. Amazon is a great starting point as you can now filter reviews by keywords.

Installing Your Motion Sensor Camera System

Though the camera system itself may seem like a complicated piece of equipment, the installation of it doesn’t have to be quite as complicated, though positioning it can take a little time.

Positioning can be a little bit of intricacy, you want it to be positioned high enough to capture as much as possible. A higher positioned camera increases the FOV and will trigger the camera as someone approaches it, not when they’re right underneath it. Setting your camera at height above reach also helps to avoid any potential tampering. Don’t place it too high though, as it could affect the quality of the image captured by the camera – you want to be able to make out the person approaching your property. If you have no other choice, then you should consider a 4K security camera for the best possible detail.

You should ensure that key access points to your property are covered such as the driveway (especially if you own vehicles), the front door and the back door.

Cameras

The video below gives you an idea of how easily a motion sensor camera is installed, though the video is specifically tailored to a model from Honeywell Home. Most motion camera sensors are set up in a similar way, and if you’re ever in doubt, you can always refer to the owners manual for additional help.

1 Inch Sensor Cameras

Final Thoughts

Heat Sensor Cameras

Motion sensor camera systems can be a great addition to a safe and secure home. It’s important to asses what you’re trying to achieve from your IP camera system and what different models can provide you with before you head out to make a purchase. If you’re well informed about what your house will need, then you can decide whether you want a PIR, dual system, a microwave pulse-type sensor, or something completely different.

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