Optimizing Your Optics

When it comes to purchasing security cameras, there are so many numbers and specifications for the end user to be aware of that it is easy to lose sight of the main objective — finding a camera that gives the best possible image.

Can you find me? Each new technology that arrives is surrounded by claims that it is to be the last word in image quality advances. In reality, though, there is no single factor that determines the quality of an image. Lenses, imagers, compression algorithms and other factors all contribute to picture quality, which will only be as good as the weakest link in the technology chain.

Examining the technology behind the numbers on the spec sheets, however, allows a better understanding of how to deliver what the customer ultimately wants — a good image.

Digital Zoom Vs. Optical Zoom: It Can Be A World Of Difference

Lens technology is the most overlooked feature of any security camera, yet it is the most important. The lens is where the image is first acquired, and although a poor imager or compression algorithm might degrade that original image, nothing can be done that will improve it after it leaves the lens.

Despite some recent hyperbole about megapixel cameras supposedly providing better images, the truth is that some of these cameras are hampered by being outfitted with inexpensive plastic lenses, which compromise the quality of the image.

Lens coatings also affect the quality of the image, and yet information on lens coatings usually doesn’t appear on spec sheets. Having the proper coatings on a lens can reduce chromatic aberration (the blending of colors at high zooms), as well as other artifacts such as smearing and ghosting that can plague some cameras.

Most camera manufacturers do not release information regarding their proprietary lens coatings; therefore a side-by-side comparison between two cameras that are identical (or as close to identical as possible)  except for the lens is always the best method of determining the quality of a camera’s optics.

Zoom ratio is another important aspect of lens technology, and it does appear on spec sheets. Some users, however, don’t understand or appreciate the difference between optical and digital zoom. 

Digital zoom ratios often have much higher numbers, and can seduce the user into thinking they are going to get a better image than they actually do. Optical zoom ratios, on the other hand, are a much better means of identifying the better lens and superior image that a security camera will provide.

As the name suggests, optical zoom involves using the actual optical capabilities of the lens to zoom in on an image object. Distortion is minimized because the image itself is not being altered. Optical zoom is comparable to looking through a telescope; the image remains the same, but the power of the lens brings the object image closer.

Digital zoom generally occurs after the optical zoom has reached its maximum, and the user wants to zoom even closer. With digital zoom, the image is being manipulated to enlarge the pixels, making the image appear larger. This is similar to magnifying a jpeg image stored on your computer; you aren’t being brought any closer to the static image, but the computer makes it seem closer by altering pixel size to help you view a detail you may not have been able to see in the original. Since the image is being altered, it quickly loses its sharpness as you continue to enhance it.

There are certain security imaging situations, however, such as reading a license plate in a parking lot, that require a sharp image. It also depends on whether the solution is intended to merely capture what takes place or if the actual identification of specific individuals or objects is desired. In such cases a strong optical zoom is the best solution.

Some security cameras will advertise zoom ratios of more than 200x. This is largely for show, and to impress uninformed buyers. For example, in a camera with 10x optical zoom a small amount of digital zoom will provide a usable image, but as the zoom goes above 15x digital, the picture starts to break up. By 20x or 40x, the image is very poor. Anything higher than that is virtually useless.

Don’t allow your customers to be swayed by a security camera with an absurdly high digital zoom ratio. Their hopes of having a spy satellite in a tiny, dome-ready camera will quickly be dashed when they see the actual image, leaving them disappointed with their purchase — and the dealer who sold it to them.

Megapixel Has Its Drawbacks

The idea of a megapixel security camera originated in the consumer market. As megapixel still cameras and high definition televisions (HDTV) became mainstream products, users started wondering, “Wouldn’t it be great if I could have a security camera that gave me a megapixel image, too?”

The industry has rushed to meet this new demand, and the result is that megapixel cameras have created a buzz. But how much better do they actually make the picture?

As discussed earlier, a powerful imager cannot compensate for a weak lens. A megapixel imager behind a blurry image will simply make for lots of blurry pixels. The most significant current challenge with megapixel cameras is the quality of the optics in the camera. Until this is corrected, there are VGA cameras that will actually provide a better picture than their megapixel counterparts, owing it to superior lens technology.

Compression is another issue facing megapixel cameras. Anyone who has ever taken a digital photograph knows that a high-resolution image takes up significantly more storage space than a low-resolution image. What then happens when you are taking five-10 high-resolution images per second for hours at a time?

Because of the large amount of data that needs to be transmitted, highly advanced compression algorithms are needed to reduce the storage size of the video. An alternative to compression is increasing storage capacity, but that can become expensive. If the user can afford it, more storage may be the simplest and most ideal solution, but users need to be aware of the fact that more storage is required.

If the user decides not to increase their storage capacity, then they will likely have to compress the video. Increasing compression reduces video quality. Lowering the frame rate can also reduce the storage size, but too low a frame rate can compromise the effectiveness of the video.

Transmitting video over IP is a major source of problems with uncompressed megapixel video. The Internet itself can be a bit unreliable when it comes to sustained bandwidth. Archiving data remotely requires a dedicated line to avoid taxing the user’s bandwidth and also to avoid making the stream susceptible to the typical ups and downs of Internet speed.

Naturally, a dedicated line for transmitting video over IP is going to cost the user additional money, which is something they may not have considered when choosing to buy a megapixel camera.

The video can be managed by increasing the frame compression, reducing the frame size, or lowering the frame rate — all of which will result in a poorer video. Once again, as with the lens-quality issue, if the integrity of the megapixel image is being reduced to where it’s the same as a VGA camera (or worse), then there isn’t much point in the user having the added expense of a megapixel camera. 

Let Application Guide Solution

Despite what customers might think or say they want, what they really want is the best possible image that suits their needs, at a reasonable price. This is far and away the most important thing for them to understand.

The best image does not come from a spec sheet, it comes from quality components. A dune-buggy and a sports ca
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