防犯カメラはどこまで見える? (究極のガイド 2022)

これは、人々が尋ねる最も一般的な質問の 1 つです:監視カメラはどこまで見ることができますか?カメラが見える距離は？防犯カメラが物や人を検知できる範囲は?

設置されたカメラが必要な距離で表示/記録できることを確認する必要があるため、これは重要な仕様です。このガイドでは、カメラが実際に物を見ることができる距離を決定する要因について説明します。

一般的に言えば、通常のセキュリティ カメラは、レンズのサイズ、解像度、センサーの種類に応じて、10 ～ 70 フィート (3 ～ 23 m) の範囲で見ることができます。ただし、1,000 フィートを超える距離で見ることができる PTZ カメラなど、他の種類のカメラもあります。

ガイド:セキュリティ カメラはどこまで見通せますか?

カメラが提供できる距離と許容範囲を知ることで、財産をより適切に保護し、死角を回避することができます。侵入者を識別したり、車の特徴やナンバー プレートを検出したりできるように、画像は十分に鮮明である必要があります。

防犯カメラを購入する前に、設置場所を調べて、設置場所と監視対象のメイン スポーツとの距離を確認する必要があります。次に、これらの範囲に従ってカメラを購入します。

考慮すべきもう 1 つの点は、一般的な領域をキャプチャするだけでよいのか、それとも入り口やナンバー プレートなどで顔を検出する必要があるのか​​ということです。ほとんどの場合、通常のカメラが必要ですが、場合によっては特別なモデルが必要になることもあります。ここでいくつかの説明が得られます。

防犯カメラの範囲を決定する多くの要因と仕様があります。一部のカメラは遠くを見ることができますが、より狭い角度で見ることができます。他の人は非常に広い角度で見ることができますが、近くで見ることができます.

これらすべての要因を理解し、ニーズにより適したカメラを選択する必要があります。実際、CCTV カメラの範囲距離は、主に次の要因の影響を受けます。

視野角 (視野)

Field of view is the area of coverage that the camera can ‘see’ within a scene and this depends on several factors. The wider the field of view, the more you can see but fewer details. (the objects appear small and far away).

The narrower the viewing angle, the less scene you can see, but the clearer the image (clear objects, closer distance). The diagram below illustrates the field of view.
The security cameras can come with a fixed viewing angle but some are available on adjustable lenses that enable the user to adjust the viewing angle. For more details, check the next section of this guide.

The lens size

Also known as the focal length, the lens size of the security camera is the number one factor that determines the distance and the angle that the security camera can see. Technically is the distance between the center of the lens and its focus.

The lens size is measured in mm and it comes in two types:

Fixed lens. It’s standard and it’s usually available in 2.8mm, 3.6mm, 4mm, 6mm, 12mm, etc. Once you buy this type of camera, you can’t change the lens size. It’s glued in and fixed.

Varifocal lens. This type is not fixed and can be adjusted in the worksite to better fit the installation needs. The common varifocal lens size is 2.8mm-12mm which means the lens can be adjusted starting from 2.8mm and up to 12mm.

To understand how the lens size correlates to the distance and the viewing angle, remember this:

• The smaller the lens size, the wider the field of view. The camera will provide clear images at a wide viewing angle, but it cannot see clearly at great distances.
• The larger the lens size, the narrower the field of view. The camera will provide clear images at a great distance, but the angles will be narrow.

If you need a wider viewing angle, then you should go for a low lens size camera. If you need more distance and clarity (but narrower angle) then you can go for a 4mm camera (for example if you need to see your driveway). Usually, a 4mm lens camera is good for a distance around 40-50 feet.

Another type of camera is the PTZ style camera (pan-tilt-zoom) which has an adjustable lens size that can be controlled remotely and the distance can go up to hundreds of feet (depending on the model). Obviously, these cameras are expensive.

Resolution

Resolution enables the camera to make out the details which are important if you need to identify people and objects. The higher the resolution, the clearer the image, especially during the nighttime.

Nowadays the price of high-resolution cameras has gone down and you can get really clear images at an affordable price. For example, 4MP or 8MP cameras provide clear footage and are not that expensive.

You can go for IP security cameras that use network cables or even HD over coax that use coaxial siamese wiring (one for the power, the other for the data). A higher resolution means that the sensor provides more pixels for the picture which in turn generates a clearer, sharper and cleaner image.

For example, a 4MP camera means that the picture is created using 4 million pixels. On an 8 MP camera, there are 8 million pixels on each frame. This makes the digital zoom feel smoother (and cleared). That way you can identify the subjects at quite a distance (40-70 feet). The diagram below shows various resolutions on security cameras.

Installation location

The installation spot is important on how far away the camera can see, specifically the height where the camera is mounted. Obviously, the farther the object, the more difficult is to see. Unless you choose the right lens (in this case, a higher lens size).

Before adding any camera, you need to determine the distance that you’re trying to see on the camera. Then purchase the camera with the right specs (that can detect the objects in your location). This process is part of the planning and it must be done.

The camera’s quality

There are a lot of factors that create quality on a camera. And not all security cameras are the same; the price tells something about their hardware quality.

The general rule is to avoid cheap cameras, especially the cameras that claim high-resolution and great night vision at a fraction of the price. You should go the medium range or the high-end if you can afford it.

A good camera has good hardware, meaning good sensors, a good processor, good IR light, and reliable software. The no-name cheap cameras miss a lot of this stuff and quite often they don’t even last that long.

Moreover, security cameras from well-known brands are supported by the manufacturer, get firmware updates and the seller provides a warranty.

Table:The distance that the camera can see based on the lens size

Common cameras are the 3.6mm ones that have an angle of view around 90 degrees. This allows you to identify people at around 20 feet of distance. This camera is great for giving a general overview of the area, but it can’t identify people only if they come close to the sensor.

Another type of camera comes with an 8mm lens and it provides a view angle of 40 degrees. This camera will identify people at around 40 feet. So, the viewing angle is narrower, but you can clearly see people at double distance compared with the 3.6mm cameras.

Varifocal cameras come with an adjustable lens size of 2.8-12mm. You can manually adjust it between the ultra-wide 2.8mm to the telephoto 12mm. At 28mm the viewing angle is around 100 degrees but the identification distance is only around 10 feet. At 12mm you will get a 30-degree viewing angle and the identification range at 50 feet.

Another special camera is the 6-22mm varifocal lens camera. At 6mm the viewing angle is around 40 degrees and identifying range at 35 feet. However, at 22mm the viewing angle is around 16 degrees and the identification distance at 80 feet.

If that’s enough, you can use 5-55mm varifocal cameras. This type is used for specific installation conditions and allows identification at around 230 feet (viewing angle is 7 degrees, very narrow). Below we’ve compiled the table that can help you find out how far the cameras can see (accompanied by the viewing angle).

Lens Size	Viewing Angle	Identification Distance
2.8mm	103°	10ft (3m)
3.6mm	94°	20ft (6m)
5mm	50°	30ft (9m)
6mm	43°	35ft (10.6)
8mm	42°	40ft (12m)
12mm	30°	50ft (15.2m)
22mm	16°	80ft (24.3m)
50mm	7°	230ft (70m)

How to monitor spots at a (far) distance?

If you need to monitor a spot that is at quite a distance, here are some tips to help you make the right choice:

• Choose security cameras that come with varifocal lenses, meaning you can manually adjust the lens to get the right identification range. You can install the camera and then play with the zoom toggle until you’re happy with the result. Common cameras:2.8-12mm or 5-22mm varifocal lens.
• Higher resolution cameras such as 4MP, 8MP, or 4K ones can provide more pixels on the image which creates a clearer, bigger and sharper image.
• If the distance is quite far, you may use PTZ cameras (pan-tilt-zoom). These cameras come with powerful motorized lenses that can be adjusted and the identification range can go up to hundreds of feet (depending on the camera model). Obviously, the PTZ cameras are expensive and large in size.
• Purchase cameras from reputable companies that have good reviews and that support their products.
• Install the cameras close to the monitoring spot.

結論

It’s crucial to understand the viewing angle and the identification range before purchasing and installing any security cameras. You need to inspect the job site and determine where the cameras will be installed and at what distance are they supposed to see.

Then you can get the correct camera. Consult the table above to find out which lens size works better for your situation. If you plan to build a security system from the scratch, you can check out our recommendation list for security camera systems .