Surveillance camera lens are slowly beginning to evolve with the technology that supports them.  before the digital age, a good majority of the surveillance cameras required that a lens be purchased for each camera.  Presently, some cameras still work that way, but the vast majority has the lens built right into the camera.  These lenses are often referred to as “board lenses.”

There are three major types of digital video camera based on their shape, the box type, the bullet type, and the dome type.  Basically the bullet and dome type cameras come with a lens already built into the unit.  this is often referred to as a board lens.  The box camera however, almost always requires the purchase of a lens.

As far as the lenses go, there are two different types of surveillance camera lenses, fixed and varifocal.  Fixed lenses do exactly what their name implies; they stay fixed in a certain immobile position.  Varifocal lenses have the ability to change their focal length either manually or remotely depending on the lens.

This means that for fixed lenses, the size of the field of view never changes; the lens can’t alter its own focal length so the width of the capture shot never changes.  this is great for use where there is no need to mess with changing the focal length regularly such as monitoring a parking lot, an entrance or exit, and other uses where zooming in on a subject or object is really not required and the camera will not be moved around a lot.

Varifocal lenses on the other hand, can move in and out changing the size of their focal length.  this is particularly handy when it is necessary to change the camera’s field of view to accommodate moving objects, tight shots, etc.  The focal length of a varifocal surveillance camera lens is normally expressed in millimeters (mm).  for example a fixed camera lens with a focal length of 3.0 mm will produce a fairly wide angle shot, whereas a focal length of 15.5mm will produce a narrow angle shot.

The nice thing about a varifocal lens is, depending on how it is made, you can get a focal length as small as possible and any focal length in between its maximum focal length.  It’s important to note that some of these varifocal lenses must be moved manually (by hand) while some our connected to a motor that drives the lens and is controlled remotely.

As long as we are on the topic of surveillance camera lenses, we’ll also mention a few of the characteristics of lenses that you probably should be aware of in addition to just focal length.  Four other points come to mind:  1. Depth of field; 2. F stop; 3. CS or C mount; and 4. Manual or Auto Iris.

Depth of Field

The depth of field is the distance from the camera to the object at which remains in focus.   Generally, the higher the F stop and tighter the Iris positions, the more objects that will be in focus.  In other words, a large Depth of Field means almost all objects in the Field of View can be in focus.  on the other hand, a small Depth of Field will only allow a small section of the Field of View in focus.

The F stop is the foacl length divided by the effective aperture diameter.  In much simpler terms, the F Stop is an indication of the speed of the lens.  Since light must pass through the lens to the sensor, the F Stop gives us an idea of how much light it will absorb during the process.  A low F Stop lens is very efficient whereas a high F stop lens will require a lot of light.

There are two standard surveillance camera lens mounts the “CS” and the “C.”  The difference between the C and CS is found in the distance between the lens and the CCD (Charged Coupled Device) or CMOS (Complementary Metal Oxide Semiconductor).  The C mount distance is 17.5mm while the CS mount is 12.5mm.

The iris works with the surveillance camera lens to control the amount of light entering the camera via the sensor.  for cameras mounted in positions that have changing light sources, it is a good idea to use a lens with an automatic iris.  for cameras used inside or in environments where the light conditions seldom ever change, manual irises are sufficient.

Tags: camera lens, camera surveillance lens, lenses, security camera, surveillance, surveillance camera lens

this entry was posted on Monday, July 11th, 2011 at 8:37 am and is filed under Security Camera. you can follow any responses to this entry through the RSS 2.0 feed. you can leave a response, or trackback from your own site.

If you are like one of an estimated 75 million owners of a digital camera, at some point in time, your camera will more than likely develop one or more problems and would be in need of digital camera repair. Common problems include cracked LCDs, broken battery doors, jammed lenses or board level problems.

There are a set of digital camera models however, that develop their own unique problems, all stemming back to a batch of defective CCDs that Sony produced and used in these camera models.

To start with, what is a CCD? A CCD is a Charged-Coupled Device, that “enables the transportation of analog signals through successive stages and are used as a form of memory or delaying samples of analog signals”.

Now for that in English: In the digital camera world, CCDs are used by the camera to capture the image that is shown by the lens, translate it into a digital signal and send it along to the image processor to be converted and saved to the memory card.

What’s the big deal with the faulty CCD? Well Sony produced a series of CCDs for various digital cameras between the years of 2003 and 2005, for at least 20 different models. And in higher heat and humidity conditions, the CCDs would begin to fail, producing some crazy looking images or causing a black screen to show on your camera (Before you starting thinking your camera has a bad CCD, PLEASE check and make sure your “display” button is not pressed and just shutting the LCD off).

So what does this mean for the consumer? Simple: If you own a camera that is covered under the Sony CCD recall, and your camera develops a problem as described above, you can generally send your camera to the manufacturer and get the CCD repaired for free. The largest affected manufacturers are Canon, Konica Minolta(now part of Sony) and Sony, but luckily for consumers, these manufacturers are standing behind their products and fixing their faulty CCDs. At one time the manufacturers were just replacing the cameras with new models, but lately it seems, they have gotten the CCDs fixed and are replacing them for you. Same camera, but you get a new, updated CCD and many more years of memories!

As Sony is the original sensor manufacturer for all of the other manufacturers’ products listed (and given the vast array of products that they manufacture themselves) it should come as no great surprise that Sony has by far, the greatest number of affected products. This should not be taken as indicating any inherent deficiency in Sony products beyond the now discontinued sensors.

Don’t throw your digital camera away if it has a bad CCD and it is covered under this recall, get it repaired for free! The best part about having the manufacturer repair your camera under this recall is that they will inspect, test, calibrate and update the camera as well as replacing the CCD with an updated version that will not fail as the first one did!

If your camera takes only solid black photos, or blurry pink/purple photos, call your manufacturer and ask them if the camera is on the CCD recall list today! If your camera is on the CCD recall list and you do not have this problem, YOU WILL in the future, so get it repaired now before the recall ends!

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Help applying the critical lens, “The difficulty in life is the choice…” to The Great Gatsby?

I haven’t read The Great Gatsby in years and hardly remember any of the details. If anyone could help me out with this critical lens essay, I’d very much appreciate it.
I need two examples from The Great Gatsby that relate back and agree with the quote: “the difficulty in life is the choice…” by George Moore in The Bending of the Bough, 1900.

Please read this classic by yourself so you can learn from it. We don’t want to your homework for you. Enoy the book.