Page 28 - Security Today, March 2017

A Line of Sight The lens is a critical component on any camera
BVy Fredrik Nilsson
ideo surveillance is both a science and an art. Suc- cess often depends on whether you match the right camera with the right lens. An optimum pairing can give you a forensic record rich in visual detail. A poor pairing could leave you clueless.
A Brief History
Twenty years ago most cameras sold were fixed box cameras with exchangeable lenses. Since many cameras were sold without a lens, aftermarket lenses became a big business. Even so, most cameras op- erated on the same 4CIF resolution. For surveillance purposes, the top selection criterion was the focal length of the lens. Fast forward to today, and the selection process has become a lot more complex. With the abundance of lenses and cameras and the variety of resolu- tions and image enhancing technologies on the market, matching the right camera with the right lens can be quite a challenge. Fortunately, camera vendors today are simplifying the selection process by pack- aging a majority of their cameras with complementing lenses.
As demands for ever-sharper image quality continues to grow, vid- eo camera manufacturers have begun looking to technology from the
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consumer electronics industry to meet the challenge. Now, we have 15-30 megapixels video cameras using Single-Lens Reflex (SLR), a crossover from the professional photography market. Like their pho- tographic camera counterparts, new high-megapixel SLR video cam- eras use exchangeable lenses further expanding user options. So what should users know that can help with the selection process?
Understanding Lens Technology
A camera lens is an assembly of multiple individual lenses of differ- ent shape and materials (glass/plastic) that are mounted at different distances. The quality of the lens material, the coatings on a lens, and how it’s assembled influence the quality and resolution a lens can provide. Usually the most difficult task is to keep each glass element in the exact correct position to get a perfect image.
Determining Resolution
The goal of a lens is to be able to distinguish small details in every pixel of the sen sor. If the resolution of the lens is too low, a small detail will be spread over many pixels of the sensor, creating an image that isn’t sharp.
CAMERA LENSES