Posts Tagged ‘ varifocal lense powered cameras’



What Is A Varifocal Security Camera?

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Monday, November 26th, 2012

What Is A Varifocal Security CameraWhat Is A Varifocal Security Camera?

One of the best values in security cameras are those equipped with a varifocal lens. These lenses come for a variety of camera styles with the two most popular choices being very-focal lenses on dome cameras and box cameras.

Varifocal Lenses Are Great For Businesses That Plan to Expand

These lenses are perfect in many situations. The first situation is a business that plans to expand to a new location someday. When a camera is equipped with a varifocal lens, then the business owner can easily move the camera to a new location. Adjusting the camera at the new location can easily be accomplished just by adjusting the focal length of the lens.

Varifocal Lenses Are Great For Homeowners On The Move

Many homeowners enjoy this benefit as the camera equipped with a varifocal lens can easily be packed up and moved to a new location. The homeowner may choose to move the camera when they move to a larger property or a smaller property and the lens can easily be adjusted to the new location.

Varifocal Lenses Provide Flexibility

The varifocal lens also makes a great choice for business owners and homeowners who may not be exactly sure what size of lens they need. With fixed distance lenses, the business owner or homeowner must guess at what length of lens that they need. If they guess wrong, then the whole unit must be returned if allowed or sold as a second hand camera costing both time and frustration.

Change Location Of Recording Without Anyone Knowing

These lenses are also super at changing what the camera is recording without having to change the camera position. Without moving the camera, it is possible to record many different situations. This is particularly useful in a commercial setting when you may want to watch one situation one day and another situation the next. The lens will also allow you to change the angle at which you see a situation.

Many people are familiar with the zoom feature of a digital camera and the varifocal lens on a security system works very similar to the lens on that camera. Just like having more zoom ability on a digital camera, the wider the range of objects this camera can be focused on, usually by turning a knob on the outside of the camera’s housing.

Dome Varifocal Security Cameras

Dome security cameras can be equipped with varifocal lenses for both indoor and outdoor use depending on the housing chosen. The most common varifocal lens on dome cameras is the 3.6 mm to 8 mm lens. Remember that the wider the range of numbers the more choices you have when using the camera. Cameras with a 3.6 mm to 8 mm lens have a maximum angle of viewing of 79.22 degrees and a minimum angle of viewing of 33.4 degrees. It is important to look at the distance that you want to install the dome security camera from where the action will likely occur. The smaller the millimeter number the closer the camera will need to be to the action, but the camera will have a wide area where it will What Is A Varifocal Security Camera record the action. The larger the millimeters number the smaller the area that the camera will record the action, but the action can be recorded from further away.

In order to determine the right focal length consider these facts. If you are watching a parking lot with a lower millimeter lens setting, then you will be able to see about six cars parked about 15 feet away. You will be able to see the make and model of the car, but very little else. If you use a camera with a higher millimeter lens, you will be able to see more details, such as car license plates and face details, but you will be able to see very little space.

Infrared Dome Security Camera with Varifocal Lenses

These cameras can be equipped with different types of operating systems. For example, many business owners and homeowners choose infrared security camera with varifocal lenses. These cameras offer the owner the ability to use the camera when no light is available. These cameras emit a small LED light that provides enough light for the camera to operate. It is important to look for a camera with IR power that matches the focal length, as the lights will only broadcast so far.

Day/Night Dome Security Cameras with Varifocal Lenses

Others choose day/night cameras with varifocal lenses. These cameras are equipped with special mirrors that collect any available light and use it to produce the footage. As more light is available, the camera will take colored pictures, but in low light situations, the pictures will have a green tint.

Daytime Dome Security Cameras with Varifocal Lenses

These cameras operate with the available light, so if there are no light these cameras will not operate. They are great in many situations where light is available all the time. An example would be inside a retail store where the lights are left on even at night.

Other Considerations When Buying Dome Security Cameras With Varifocal Lenses

Whichever dome security cameras with a varifocal lens the user chooses to buy, the buyer needs to think about other aspects. The buyer needs to think about how the footage will be viewed. There are several viewing options including a dedicated VCR, connecting it to a computer monitor or watching it on a smart phone. It is also important to consider who will monitor the footage. Some business owners will choose to monitor their own, some will assign a staff person to do this job and others will hire an outside company to do the monitoring.

Resolution on Dome Security Cameras with Varifocal Lenses

The buyer of a security system will want to consider the security systems resolution. This is measured in either TV lines or in megapixels. The higher the cameras resolution, the better the details that can be seen in the footage. The colors will also be truer to real life. A 1.2MP camera has 3.5 times the resolution of an analog camera in its largest format. Therefore most users find megapixels cameras the better buy.

Sensors on Dome Security Cameras with Varifocal Lenses

A very important consideration when buying a dome security camera with varifocal lens is the size of the sensor. The smaller the sensor, often called a CCD chip, the narrower the angle of view. Sensors in these cameras usually come in four different sizes, which are ¼ inch, 1/3 inch, ½ inch and 2/3 inch. If you choose a camera with a ¼ inch sensor then the maximum angle of the field of view is 57.77 degrees and the minimum field of view is 22.62 degrees. If you choose the 1/3 inch sensor, then the maximum angle of the field of view is 79.22 degrees and the minimum is 33.4 degrees. If you choose the half-inch sensor, then the maximum angle of the field of view is 95.63 degrees and the minimum field of view is 43.6 degrees. When you choose the largest sensor, the largest field of view is 113.22 degrees and the smallest field of view is 57.62 degrees.

What Is A Varifocal Security Camera Varifocal Lens Box Camera

Many homeowners and business owners prefer box cameras. These cameras are great because they deter many criminals because of the mere sight of the camera. The most common varifocal lens on the box camera is the 3millimeter to 15millimeter. This gives the user a wide range of angles to choose from when installing the camera inside or outside in protective housing. Just like with the dome cameras, varifocal lenses on box cameras smallest settings give the widest field of view with 15 millimeters giving the narrowest point of view.

Varifocal Lens Box Camera Sensors

It is important to consider the sensor when buying a varifocal lens box camera sensor. Again, like with the dome security camera the user generally has four choices. It is important to notice that the sensor controls the distance the camera can be placed from the target.

Varifocal Lens Bullet Camera

Bullet security cameras can also be equipped with varifocal lenses with the most common being 2.8 to 10mm. These cameras can also be equipped with the four different size sensors. It is important to consider the different combinations for this camera.

Costs

Most varifocal lenses cost about 20 to 30 percent more than a fixed lens camera, but consider the flexibility that is afforded with these lenses. One can move the camera to accommodate different situations. One can adjust the length of the lens to get the best picture. Furthermore, a person can buy cameras with different sensors to further expand their flexibility. Making sure that you buy the best camera for your money will assure that you are happy with the choice that you made.

The best process to use when choosing a camera is to choose the location that you want to put the camera in and then choose the style of camera that you want to install. Next, consider buying a camera with a varifocal lens. Then choose the size of sensor that is best for what you want to accomplish now and in the future. Finally, consider the resolution you want in the camera. All of these will factor into the price that you pay. Contact Security Camera King Today!

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Varifocal Camera

Written By:
Thursday, October 20th, 2011

Security cameras utilize two basic lens types based on focusing parameters.  These are called fixed lens cameras and varifocal cameras.  Fixed lenses have a “fixed” or constant, unchangeable focal length while varifocal lenses have a focal length that can vary. A more familiar term used for electric powered varifocal lenses is a “Zoom” lens; we will concentrate on the varifocal type in the following article.

In addition to the focusing characteristics of the lens, light requirements must also be considered.  The light that is allowed to penetrate through the lens and strike the electronic sensor chip is normally controlled by a mechanical device known as an “iris.”  The iris may be fixed, manual, or automatic.  This refers to how the iris makes the light opening, called the aperture, smaller or larger. The aperture is equivalent to the human eyeball’s pupil.  In very low light settings the aperture needs to be open wide to allow enough light to strike the sensor chip.  However, in bright light conditions, the aperture is very small to prevent too much light from flooding the sensor chip.

If a security camera is used indoors in a setting that has a constant intensity of adequate light (i.e., a store, a warehouse, or a well lit room), then a “Fixed Iris Lens” should perform adequately to serve your needs.  But if the actual field of view may need to change to a tight shot and back again, a varifocal camera is the answer.

In settings where the light conditions can vary from dark to bright (i.e., outside or a camera aimed at an outside window) an “Auto Iris Lens” will be needed to compensate and adjust for the varying light levels.

Finally, in light conditions that are constant for long periods of time but change from dark to light or light to dark, a “Manual Iris Lens” can be used.  These lenses’ apertures are changed by hand to provide the optimum light exposure.

Lenses are created using a combination of Fixed and Varifocal parameters with Fixed Iris, Auto Iris, or Manual Iris apertures.  Most security camera lenses’ focal lengths vary from 3.6 mm to 16 mm for fixed focal length lenses, to well over 70mm for varifocal cameras.  A short focal length will yield a wide angle of view and a long focal length will yield a narrow angle of view

The actual mathematical formula used to calculate the width and height of the area covered is Width = Camera Horizontal Format X Distance/Focal length and Height = Camera Vertical Format X Distance/Focal length.

In this formula, values for the Camera’s Horizontal and Vertical Format are the size of the CCD or CMOS chip expressed in MILLIMETERS, not inches, with the pictures aspect ratio of 4:3.  For example, for a 1/3 inch CMOS chip the vertical size of the chip in mm is 3.7 mm and the horizontal size is 4.9 mm.  Use the vertical format value of 3.7 mm to calculate height and the horizontal format value of 4.9 mm to calculate width.

Varifocal cameras are very versatile and easy to work with.  There are different types of varifocal cameras just like there are different types of irises for cameras as described above.  Some varifocal cameras are manual varifocal cameras which means you must physically change the focal length on the camera.  Others are automatic and can be done through electronic controls associated with the DVR.

The key is to decide whether you will require a varifocal camera or not.   A camera placed at the end of a fairly straight, long driveway would be a good candidate for a varifocal camera as you can zoom in on objects (like cars and people) at the end of the driveway but as the object comes up the driveway you can still keep them in focus and good view.

On the other hand, a camera pointed at a doorway to simply monitor the movement through the doorway would not need to be a varifocal camera; a fixed lens camera would suffice.

As a side note:  Most all of the disguised or hidden cameras have 3.7 mm wide angle lenses and are fixed lenses.  The lens on these cameras is made such that

there is the maximum amount of distance that stays in focus without the use of a varifocal camera.

If you have any questions regarding varifocal lens or varifocal cameras, contact one of our security experts today via on-line “Live Chat” or by telephone at 866-573-8878 Monday through Friday from 9AM to 6 PM EST.

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