How Do Hidden Spy Cameras Work?

A hidden surveillance camera gives you the ability to monitor your home or apartment remotely, through a simple mobile application installed on your smartphone. Hidden cameras are also known as spy cameras, and their main purpose is to record people without their knowledge. But how they actually work? Let’s find out!

How Do Hidden Spy Cameras Work?

So How do Hidden Spy Cameras Work? A hidden spy camera broadcasts the video using the wireless transmission to send and receive an image. First, it detects the image through the lens and then transmits it with the help of a radio transmitter in the form of a radio signal on a particular frequency to the device where the image is displayed on the video screen.

When we use the term “hidden camera” it means that the camera is not visible to the subject that is being filmed. For that reason, these cameras must be tiny and inconspicuous. If you want to know more about hidden spy cameras and their features, continue to read this article.

The Basics: Working Principle

The wireless spy cameras have a radio controller, thanks to which it is able to communicate with a wireless router or an Internet box. The camera, therefore, belongs to the home computer network, just like tablets, computers, and other game consoles. This wireless link offers the user the possibility to connect to the camera remotely. In practice, it is usually enough for the user to install a mobile application on his smartphone.

Step-by-Step Guide On How Hidden Spy Cameras Work

When the user is at work, on vacation, or on the road, the app connects to the camera wirelessly through the home internet connection. Once communication is established, the user consults the images sent by the camera live. It also accesses features such as zooming, moving the lens, or activating the night vision if the device is equipped. At the same time, he can remotely control the recording of images captured by the camera, either directly within the latter (by adding a microSD type memory card), or on his own phone.

Since the wireless spy camera relies on the home’s Internet connection to send its images, it is not possible to connect to it if there is no internet. The quality of the images transferred also depends on the connection to the Internet (upload capacity, ie data sending) as well as the bandwidth of the local wireless network. 

Keep in mind that Hidden Spy Cameras can Also Record the Sound.

Basic Hidden Spy Camera Parts

Every hidden spy camera consists of these 3 components:

  • The Camera

A hidden spy camera can be wireless or wired. Their main purpose is to capture the footage of the area that is being monitored. The wireless hidden camera transmits a video signal to a receiver where the image is recorded or just viewed. Wired hidden cameras are connected by a cable.

  • Recording Device 

A recording device is used to store footage that is recorded by a hidden spy camera. Most recordings are stored on the internal hard drive or on the micro SD card that comes with the camera.

  • Monitor 

The monitor is the device where you view the recorded videos or the videos in real-time. In most cases, the footage is viewed on a mobile phone or on a PC or tablet.

Process Of Transmitting and Receiving The Image

1. Wireless Basics

Hidden spy cameras use wireless transmission to send and receive a image, which makes them easier to hide and convenient to use. Therefore it is not necessary to have a cable from the camera to the receiver to get a image, but some models come with cable cause they need to be connected to a power source so they could work.

2. Detecting the Image

The wireless hidden camera capture the images with the help of light that comes through the lens. The light detectors only measures red, green or blue light, and then all of three photo detectors are combined to display a complete picture. Some wireless detectors come with a motor and a motion detector, with which you can follow all the movements in the area.

3. Transmitting the Image

All wireless hidden cameras have built-in radio transmitter that turns the image that is recorded into a radio signal on a particular frequency. That signal can be broadcast to a receiver only within the building.Then receiver picks the signal and turns it back into an image.

4. Using the Footage

The receiver has multiple functions, depending on its purpose. If the wireless spy camera wants to continue surveillance, the image is displayed on the video screen in real-time, but the image can also be recorded on specific storage media or to a PC hard drive. Today, mobile phones are most commonly used to monitor the footage from hidden surveillance cameras.

The Camera Lens

Structurally, the camera lens is a complex system of lenses enclosed in a frame and mutually compensating for optical distortion. Collects and projects light energy onto a light sensor to form an optical image.

The main parameter is the focal length (that is measured in millimeters), which determines the image scale and viewing angle. It is the distance from the axis of the lens assembly to focus (the point of intersection of initially parallel rays after passing through the lens).  The shorter the focal length, the larger the field of view. The 2.8 mm lens provides video surveillance in a sector with a viewing angle of ~ 100º. The higher the focus of the camera (for example, 8 mm), the smaller the angle of view, but the longer the distance to the object of observation required for high-quality shooting.

Video surveillance systems have different tasks, therefore, spy cameras use different types of short-focus, long-focus, and ultra-long-focus lenses: fixed focal length, variable focal length, motorized, and fisheye.

How Hidden Cameras Are Built?

Most hidden (spy) cameras are built into commonly used objects such as alarm clocks, televisions, mobile phones, toys, ink pen caps, etc. They are mostly used for home surveillance but can also be used for industrial spying. For example, you will use your hidden camera to take a look inside your house during the holidays in order to verify that no one has entered. For that reason, the spy cameras are built into objects that can easily fit into the home environment so that they are hard to notice.

How To Install a Hidden Camera?

Installing a hidden camera does not present any particular difficulty; you have to unpack the camera, plug it in or charge it, choose its location, then turn it on and connect it to the home network. This last step is often the most tedious since it is necessary to connect to the camera interface to enter the WEP or WPA security key of the WiFi network. The intervention of a professional is also recommended if you plan to integrate your camera into your alarm system and make a more advanced security system.

You have here 2 interesting articles on How to Set up a Hidden Camera in Your Bathroom and How to Hide a Camera in Your Bedroom.

Main Tech Specifications Of Hidden Spy Cameras

Tech Specs Of Hidden Spy Cameras

The Technical Elements of a Spy Camera

  • Image Quality: The image quality is determined by the display resolution.
  • The Sensor: The essential element, positioned behind the lens, which captures the light
  • Brightness (LUX): Brightness is expressed in LUX (between 0, total darkness, and 50,000 lux).
  • The Objective: It varies according to the desired viewing angle.

The Different Categories of Hidden Cameras

  • Infrared Cameras: At night, they use light-emitting diodes placed around their lens to locate infrared radiation (heat waves) and retransmit the images in black and white.
  • Day/Night Cameras: They automatically switch to day or night mode depending on the level of light.
  • Motorized domes (rotations possible) and spy cameras (which blend into the background).

Spy Camera Resolution Chart

The higher the resolution of the spy camera, the higher the quality and detail of the image. Often, 2 megapixels (Full HD) resolution is sufficient, supported by most modern monitors.

The most common resolution are:

  • HD (720p) – 1280×720 (1 megapixel) – medium resolution, suitable for general assessment of the area of ​​interest.
  • SXGA (960p) – 1280×960 (1.3 megapixel) – increased number of pixels vertically for a specific scene.
  • Full HD (1080p) – 1920×1080 (2 MP) – resolution with the ability to identify a person.
  • Quad HD (1440p) – 2560×1440 (4MP) – Improved detail for moderate bandwidth requirements.
  • 5 MP – 2560×1920 (5MP) – High detail, clear picture.
  • 4K Ultra HD (2160p) – 3840×2160 (8MP) – excellent image quality, digital zoom capability.

With the development of digital technologies, the trend towards an increase in the number of effective pixels is growing, although the high resolution is only relevant for objects where you need to clearly see the denomination and number of a bill, recognize a license plate at a great distance, and constantly scale the picture.

Final Thoughts

We can say for sure that cameras can be found everywhere today, from home surveillance, cell phones, tablets, laptops, and now they even come in smartwatches. They all work on the same principle and the technology they have built-in is almost identical in all models. Now that you’ve learned how hidden cameras work, you have better insight and understanding the next time you use one. I hope you found this article useful.


1. Can Hidden Cameras Record Audio?

Hidden spy cameras can be equipped with one or more audio inputs and outputs, so they are capable to record audio. Some models have a built-in microphone, but if required, a professional omnidirectional, or unidirectional microphone can be connected to each spy camera with audio input (depending on the application).

2. How Long Can Hidden Cameras Record?

The hidden spy cameras have a recording time of 60 minutes on average. This time depends on the battery capacity that they have built-in. Some spy cameras come with a cable so they can be plugged into an electrical outlet.

3. Can Camera Record in Low Light Conditions?

Yes, hidden spy cameras have a night vision mode which allows them to record even in low light conditions and during the night. Night vision mode is turn-on automatically when the camera sensors detect a dark environment.

4. How Much Footage Can Hidden Cameras Store?

It depends on the internal hard memory and the external memory (SD card) that a hidden spy camera has. If the spy camera has the ability to use SD cards, then the 256 GB will be more then enough to record a lot of hours of footage.

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