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The number one concern of end-users looking to purchase a security camera is an obvious, but occasionally misunderstood one: How good is the image the camera makes?
In the quest for the best possible image, prospective buyers typically start by consulting specification sheets, which contain a bewildering array of numbers. But numbers on a spec sheet do not tell the whole story and they can be misconstrued, resulting in an inaccurate representation of the image quality of a particular security camera.
Deconstructing the myths and misconceptions behind those numbers can help buyers understand the various factors that go into making a quality image—some of which have to be seen to be understood—and enable dealers to provide buyers with a security camera that they can be happy with. Consider these statements and how they apply to the proper deployment of proper surveillance.
"I need a megapixel camera to have a great image."
The buzz in the industry lately has revolved around "megapixel cameras," but are they really that great or just hype? The desire for megapixel cameras originates in the consumer market, where still-image megapixel cameras and HDTV sets have ingrained the idea that the more pixels you have, the better the image will be. This is true to an extent, but it's not the entire story.
Before a scene has been turned into an electrical signal by a megapixel CCD or CMOS imager, transmitted via Internet protocol or subjected to any other digital processing, it first has to be captured and that takes place in the lens.
The lens is easily the most important and yet most easily overlooked feature of any camera—especially a security camera. The lens is the "eye" of the camera and if that lens isn't the best, it doesn't matter how many pixels the imager has, the picture may still lack crucial detail. A quality lens is as important, if not more important, than the number of pixels in the imager. Some megapixel cameras have an inexpensive piece of plastic for a lens, which compromises the overall quality of the image and defeats the purpose of having a megapixel camera in the first place. Lens coatings are also an important factor in lens design. They help to reduce smearing and chromatic aberration (when colors blend together at high zoom ratios) and are another important feature.
Users should do a side-by-side comparison of the security cameras they're considering. Does the security camera reveal intricate details? How accurate is the color? Can you see any distortion? A camera with less than a megapixel sensor, but with stellar optics, might provide the better image. At the end of the day, the end user is selecting security cameras in order to be able to identify someone or something in a mission-critical application. Users should be concerned about whether or not they can recognize the person in the image or properly identify the color of their clothing, or other crucial details. If they can't see those details it doesn't matter how many megapixels their camera has.
"I want a camera with 100x zoom."
Depending on the area that the user is looking to survey, they may need a high-powered zoom on their security camera. Their first instinct will be to go for the camera that has the biggest number next to its zoom ratio. If a dealer values the buyer's trust to provide the right product, rather than the most expensive one, then it is necessary to make sure they understand the difference between optical and digital zoom.
Optical zoom is—as the name implies—zooms in on an image through the use of the lens' optical capabilities. It's almost like looking through a pair of binoculars. Because the image itself is not being modified, there is negligible distortion. The higher the optical zoom on the camera, the closer the user will be able to see.
With digital zoom, however, the image has reached its maximum optical zoom and is now being digitally enlarged for a closer look. It is similar to looking at an image on your computer and hitting the "magnify" button—things start getting soft, the image loses its sharp edges and it becomes blurry. Once you move from the optical to the digital zoom, you start losing detail, which becomes especially important for a task such as zeroing in on a license plate.
Ideally, digital zoom should be used for those times when you need just a little more detail. A security camera with 10x optical and 200x digital zoom will be good up to about 15x and then the image starts breaking up. By 20x or 40x, the image degrades further. Anything higher than that will make the image illegible. Megapixel cameras help to delay the side-effects of digital zoom because the pixels are smaller, but the benefits can be negated by the inferior lenses built into megapixel cameras. The same image can be obtained at a lower cost to the end user by using a camera with a good lens and optical zoom capabilities.
"Why would I need to compress my image?"
Another overlooked aspect of a security system is the transmission and storage of video. Megapixel cameras have a large amount of information in each frame and transmitting that information for remote viewing (video over IP) uses more bandwidth. If the user is viewing or archiving data remotely, they will be susceptible to all the ups and downs of the network's traffic speed unless there is a dedicated line, which is an added cost for the end user. In order to be able to quickly and efficiently transmit video without the added cost of a dedicated line, prospective buyers will need to evaluate frame size, compression, and rate—all of which can compromise the quality of the image.
Compression algorithms are constantly improving to reduce the amount of data needed to transmit a quality image, but the fact remains that compressing an image requires sacrificing some of its quality. Compression helps to reduce bandwidth and storage issues, especially when saving video from multiple cameras. With a megapixel camera, however, the compressed image is still going to be larger than a standard VGA image and may require additional compression to meet the user's storage capabilities—or the user may have to add additional storage. Additional compression of a megapixel image can bring the quality down to where having a megapixel camera becomes a moot point. Without a good compression algorithm, the customer is using a lot of bandwidth and storage space for an image that may or may not be better than a non-megapixel camera with a better algorithm for keeping the resolution and picture quality high.
The main concern of security camera users is to obtain a better image. Unfortunately, some users are getting herded into the megapixel arena because of the erroneous assumption that more pixels equal higher quality. But without a quality lens, good optical coatings to reduce artifacts like ghosting and chromatic aberration and efficient compression algorithms, the user is not going to get the video images they desire, regardless of how many pixels their camera has.
At the end of the day, the picture is all that matters. Specs have their place, but only up to a point. There is no spec that will necessarily guarantee good picture quality. Only a side-by-side evaluation can fully show you the picture quality that a security camera can produce. You have to see it to believe it.
Ricardo A. Chen is the manager of Technical Marketing and Sales Training for Canon's Consumer Imaging Group's Video Marketing Division.
author: By Ricardo A. Chen