A Focus on Lenses Scottsdale AZ

Lenses may not be what first come to mind when you think about the components of a video security surveillance system but they do play a crucial role. You could have the best camera in the world sending images over a quality transmission line to a stellar DVR and still get a lousy picture due to the lens either being the wrong type or out of focus. This can be the difference between catching the criminal or having the customer feel the time and money spent on the surveillance system was a giant slap in the face.

The good news is that for security dealer integrators who know what they are doing, the lens should not be the weak link in a video surveillance system. Over the past few years, lens technology has been improving. Lenses now offer better image quality and the ability to automatically readjust and refocus for changes in lighting or a moving object. Best of all, as these new technologies are being refined and improved; the prices have recently been coming down.

So what are the different lenses available today and how do you go about choosing? Take a look…

ASK THE RIGHT QUESTIONS

"The first step is to look at the application itself and ask questions," says Benjamin Rhodes, sales consultant, Kowa Optimed. His list consists of the following: "What is the location? What is the distance from the camera to the intended subjects of observation? What is the size of the intended subjects? What is the area of the intended location? What are the lighting conditions?"

Kevin Cook, regional sales manager, CBC (America), agrees that a thorough understanding of the customer's goals will lead to selecting the proper lenses for the video surveillance system. However, he also encourages dealers to make sure that the customer's expectations are realistic beforehand.

FIXED, VARIFOCAL, OR ZOOM?

When it comes to the different types of lenses, a lot of times you will hear about fixed, varifocal, or zoom. These different lens types refer to if and how the focal length changes. For a fixed lens, the focal length doesn't change. For varifocal and zoom lenses, the focal length can change—and zoom lenses have the added bonus of staying in focus while the focal length is changing.

Comparing varifocals to fixed lenses, Steve Beaulieu, national sales manager, Tamron, explains, "By using a varifocal, it takes a lot of the guesswork out of it. Years ago, you would have to take five or six lenses, and screw them on, show them to the end user, and say 'hey, do you like that?'"

If they didn't like it, according to Beaulieu, then the process of trying to focus the five or six lenses would repeat until the customer was happy. "Now with a varifocal, [a dealer] can go out there with one of those lenses and actually dial it in to exactly what the end user wants," he states.

Cook says that zoom lenses are most popular on PTZ (pan/tilt/zoom) controllers with active security personnel. However, varifocals are still the most popular lenses overall for security applications today.

DROPPING THE F-STOP

"The newest generation of lenses are very fast as compared to the older lenses," says Adam Colombo, eastern regional sales manager, Fujinon Inc. "By 'fast' I mean their f-stop ratings are greatly improved. Typically, a lens would be rated at F/1.4, but now they go down to F/0.95."

The smaller the f-stop number, the larger the aperture and thus the lens gathers light better. This usually results in better image quality.

"If you're looking at a picture, everybody's center will be good," Beaulieu says of the various lens manufacturers. "As you get out to the edge (of the image), that's where you can tell the difference between lenses."

Aspherical lenses are a big reason that images are clearer from center to edge today, says Tom Harada, general manager of components group/security systems, Pentax Corp. Due to their shape, aspherical lenses are able to reduce barrel distortion and collect more spectrums of light, which allows for a more consistent image throughout.

AVOID THE PITFALLS

Beaulieu says that the general public often sees crummy video feeds of real crimes on their TVs and comes away thinking that the products produced by the video security surveillance industry are not any good. However, according to him, it doesn't need to be that way. In many of these cases, the images are poor because the wrong camera or lens was used for that application.

A common mistake that Beaulieu sees is when people will point a standard camera out the window. The camera will work fine in moderate light during the day. Yet, the image quality suffers greatly under bright sun or in the darkness of night.

But of course, technology exists today to remedy this problem. Not only are there cameras suitable for the task (such as wide dynamic range cameras), but there are lenses too. For instance, Rhodes says that the Day & Night (or infrared, "IR") lens "allows someone the luxury of not having to refocus when night falls." He adds that the Day & Night lens was made possible by "innovations like incorporating ED (extra-low dispersion) glass with an aspherical lens."

Also, be sure to know the camera's format and resolution capabilities. If your camera's format is 1/3" (the most common format today), then you will want to have a 1/3" lens. If your camera's resolution is capable of 540 TV lines, then make sure your lens is likewise. (If your camera is capable of 540 TV lines but your lens is only capable of 400, then your picture will only come out at 400).

"It is very important to choose the right products for the application, and unfortunately I think a lot of dealers don't," concludes Beaulieu. "And that's why what we see on TV is what we see."

RESOURCES

For diagrams, visit Fujinon:
www.fujinoncctv.com/pdfs/cctv0904/data_terminology.pdf

For a lens calculator, visit Tamron:
www.tamron.com/cctv/lenscalculator/

For a glossary, visit CBC (America):
www.cbcamerica.com/cctvprod/glossary.htm