what is varifocal lens in cctv cameras


what is varifocal lens in cctv cameras插图

Lens that can zoom in and out
What is the meaning of varifocal lens in CCTV camerasClosed-circuit televisionClosed-circuit television, also known as video surveillance, is the use of video cameras to transmit a signal to a specific place, on a limited set of monitors. It differs from broadcast television in that the signal is not openly transmitted, though it may employ point to point, …en.wikipedia.org? Simply put,a varifocal lens is alens that can zoom in and out. You can adjust the lens so that it captures a wider area or so that it focuses in more detail on a smaller area.

What is the role of Lens in a CCTV camera?

A camera records images through the lens using image sensors.These images (and often audio too) are transmitted to the recorder or tape,either wirelessly or by cable. ...Monitor (s) can be passively (through software) or actively (by people) monitored. CCTV networks can,and should,themselves be monitored.

How to adjust focus on a varifocal CCTV camera lens?

Steps for changing the focus of a Dome Security Camera LensRemove the foam insert slowly and carefully.Infrared LEDs should be moved to one side.Connect your camera lens to a monitor and twist the lens until it is focused.Replacing the infrared LED after adjusting the focus is the next step.Reposition the foam insert carefully around the lens.More items...

What are varifocal and auto-iris for CCTV cameras?

Terms varifocal and Auto Iris refer to CCTV Camera lens functions . A varifocal lens is a camera lens with variable focal length in which focus changes as focal length (and magnification) changes, as compared to parfocal (true) zoom lens, which remains in focus as the lens zooms (focal length and magnification change).

Does pinhole camera use a type of CCTV lens?

The Pinhole camera is the elementary camera that doesn’t have a lens, however it comes with a small aperture, and has a light-proof box with a small hole on one side. The light from the object goes through the aperture and it projects the inverted image on the opposite end of the box, which is known as camera obscura effect.

What is the size of a varifocal lens?

Varifocal lenses come in various apertures. These are the general lense sizes. 2.8-12mm lens, 3.5-8mm lens, 6-60mm lens, and 5-100mm lens. The larger the aperture number, the more zoomed in the image will appear and the greater detail that can be captured.

What type of lens is used for CCTV?

There are two basic types of CCTV lenses. You can either get a fixed lens, or a vari-focal lens. A fixed lens has a set aperture that cannot be changed. They can be used for overviews or for close up detail, but they cannot be used for both or be adjusted.

What does smaller aperture mean?

The smaller the aperture number, the wider the view and less detail will be captured. Keep in mind that all lenses have a give or take. The larger the aperture, the greater the detail, but you will get less of a field of view, so the image will be narrower.

What are the different types of digital cameras?

There are basically three types of digital video cameras: 1) The dome camera; 2) The box camera; and, the bullet security camera. In this article we are going to focus our attention on the bullet security camera.

What is a varifocal CCTV camera?

Varifocal lenses are measured by their focal length. Most varifocal security cameras will have a focal length of 2.7mm-12mm (4x zoom), but they can go up to 4.5mm-135mm (30x zoom). The longer the focal length, the more you can zoom in and see details.

What does a smaller focal length mean?

On the other end, a smaller focal length means that you will have a wider field of view (FOV). A fixed lens doesn’t let you adjust the focal length, angle of view, and level of zoom. With a varifocal camera, you can adjust these settings. One very obvious benefit of a varifocal security camera is its use in identifying people or objects ...

What is the difference between a 2.8mm and a 4mm camera?

For example, a 2.8mm lens will have a slightly wider angle of view than a 4mm lens. These varifocal CCTV cameras are adjustable from a 2.8mm setting to a 12mm setting. This means that when you have the lens set to 2.8mm, or the zoomed out setting, ...

Why use a varifocal camera?

One very obvious benefit of a varifocal security camera is its use in identifying people or objects at a distance. Let’s say you have it mounted on the back of your house and zoomed out so it can see the whole backyard.

What is digital zoom?

Digital zoom basically zooms in on the pixels of the image, making them larger until the picture is blurry. This is the same result you would get if you open a picture on your computer and zoom in. The farther you zoom in the more pixelated or blurry the image will become. Usually, the varifocal cameras are more expensive since ...

Why do you zoom in closer to the fence line?

You can zoom in closer to the fence line so you can identify them in much greater detail if a crime were to happen. After a few days, they are no longer doing it so you simply return the camera to its original FOV.

How far can you see someone's face?

A narrow-angle makes it possible to recognize someone’s face from 75 and even up to 100 feet away with a 4MP camera using digital zoom, but the area you can cover is more limited.

Box Cameras

Most of these types of cameras do not come with lenses. You can purchase the Varifocal lenses separately. These are normally c-mount lenses which you can choose the right one for your application. These are one of the only types of surveillance cameras which are flexible with allowing you to choose the correct Varifocal lens for your needs.

Megapixel Varifocal Lens

Even Megapixel IP Box Cameras will use varifocal cameras. However, you need to make sure to purchase the lens that is specifically made for this type of camera because the analog c-mount lenses will not work properly with the megapixel IP box cameras.

Varifocal Bullet Security Cameras

Bullet security cameras are also known as cylinder surveillance cameras and have a great design for easy mounting and weather resistance. They are normally the choice for cameras that are going to be mounted in a high out-of-reach area outside of a building.

Varifocal Vandal Dome Security Cameras

Vandal domes are great for protecting your home or business. These vandal domes can be installed indoor or outdoor and have a weather and vandal resistant dome.

How far can a wide angle camera identify faces?

At about 50-100 foot a wide-angle lens 1080P camera will not do a tremendously good job at identifying faces. At about twenty feet a standard definition camera will also not work to identify faces, but if you are willing to pay for a varifocal standard definition camera you should go HD wide-angle. For about the same price as a standard definition varifocal, you get a higher resolution picture that extends the distance that you can identify faces while not giving up any of the wide-angle view.

What is a varifocal camera?

A varifocal camera allows you to adjust between its top and bottom limits on its view angle. This means that you have the ability to manually set both the view angle and level of zoom. Have a scenario where you need to zoom in on a gate or other access point? Use the 12mm setting (12 degrees and about 4x zoom). Need a wide-angle view? Go with 2.8 mm (109 degrees). Need something in between? Try 6mm (~45 degrees) or 9mm (~30 degrees).

What is the difference between a fixed lens and a varifocal lens?

Part 1 - What's the difference? A fixed lens doesn’t let you adjust the focal length, angle of view, and level of zoom. Almost all fixed lens security cameras have a wide-angle. With a varifocal camera, you can adjust these things. Let's look at some examples of what this means.

How to reduce viewing angle?

By increasing the focal length (the mm setting) and magnifying an area , you reduce your viewing angle, as superimposing the 12mm image on top of the 4mm one easily shows. You get a lot more detail for one area at the cost of losing a wide-angle view.

Why use a wide angle camera?

With greater distances, a wide-angle view camera will lack the ability to identify faces. It becomes necessary to use a higher millimeter lens when you are trying to identify a security threat that is further away.

How many cameras do you need to cover a square room?

Because your normal fixed lens is 75 degrees, placing a fixed lens camera in the corner of a square room, will give you a coverage map like this: This means that you really need two cameras to cover that area. With one 98 degrees camera, you could cover the whole space and not have to buy two cameras (the walls are 90 degrees).

How to get a better picture of a license plate?

By increasing the focal length, you get a much better image of the man/license plate. At ten feet, this doesn't matter very much but at larger distances (which we will show in a second) this can mean the difference between identifying a suspect and not getting a clear enough picture of their face.

Why do you need to use a digital zoom?

This is because digital zoom enlarges the original image, using less pixels to give you the view you require. With a varifocal camera you adjust the lens to focus on area of interest.

Why are some cameras priced differently?

In short, fixed lens cameras give a specific field of view, while the viewing angle of a varifocal is set during installation.

What is a varifocal camera?

Varifocal cameras. With an adjustable lens, varifocal cameras allow you to adjust until you have the perfect field of view. Unlike a pan tilt zoom models, this adaptability is used for installation only. Once your field of view is set, it stays the same, until it is adjusted.

What is remote zoom and focus?

Remote zoom and focus enables you to make small adjustments to your field of view post installation.

When you adjust the varifocal field of view, can you manually set the viewing angle and depth of field?

When you’re adjusting the varifocal field of view, you can manually set the viewing angle and depth of field. This enables you to monitor a specific of interest area within a scene.

Is a fixed lens better than a varifocal lens?

There you have it! You should now know that the lens is the difference between fixed and varifocal cameras. As well as knowing that fixed are useful for budget conscious installations which require an overview. For sites requiring precise monitoring, a varifocal would be a better choice.

Is a fixed view lens camera easy to install?

Quick and easy install. The lack of moving parts makes the installation easy. There’s no need to adjust the focal length or angle of view, just point the camera in the right direction and away you go. This makes fixed view lens cameras great for smaller businesses.

What is a varifocal lens?

varifocal lens cameras, is a camera lens with variable focal length in which focus changes as focal length (and magnification) changes, as compared to parfocal ("true") zoom lens , which remains in focus as the lens zooms ( focal length and magnification change).

What is the difference between a fixed lens and a varifocal lens?

What's the difference between fixed lens and varifocal lens cameras? fixed lens camera, is a camera lens with a fixed lens which you can't adjust the focal length, angle of view and also level of zoom. but almost of all fixed lens cameras are wide angle and also smaller than varifocal cameras. varifocal lens cameras, is a camera lens ...

How to get a better picture of a man throwing rocks?

By increasing the focal length, you get a much better image of the man throwing the rock. At 10 feet, this doesn't matter very much but at larger distances this can mean the difference between identifying a suspect and not getting a clear enough picture of their face. A varifocal camera allows you to adjust between its top ...