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CAMERA FIELD OF VIEW ISSUES ing you can monitor for intrusions that come over a fence, even less view of the sky is required. 3. GOING TO BED TOO EARLY Jobsite walks are an extremely valuable part of the security design process. Good consultants and educated site owners make these available to potential security bidders so all the unique aspects of the site are understood in the early planning phases of a security design. I'm sure you or your company has participated in many of these, but I'd be curious how many have been through a nighttime site walk. Most times these are thought as unnecessary, as a security design will typically include For nighttime coverage, the camera feld of view should align with the feld of view of the some type of consideration for low light infrared illuminator. In this illustration, you can see how camera FOVs and illuminator FOVs need to be adjusted to align. viewing: infrared (IR) illuminators, thermal cameras, etc. However, there are many sources of existing light that need ting up a camera's FOV is not considering the FOV of the ilto be considered when setting a FOV: existing facility lights, luminant. Whether you are using IR illumination, or even periodic headlights, lights from adjacent facilities, sunrise/ white light illumination, for nighttime monitoring the most sunset, refective light (water, windows), etc. Light sources important aspect is not the FOV of the camera, but rather the can play havoc on cameras in a variety of ways, so it's impor- FOV of the IR illuminator or visible light source. tant to know where they are and to plan your FOV around If you have ever viewed a camera at night with little or no them if possible. Unfortunately, if you don't plan on staying illumination then you understand why this is important, you up for the nightshift, you won't have the opportunity to ex- basically get a black video feed. If you want your nighttime FOV plore where these lighting issues might be lurking. to correspond with your daylight FOV, then you need to ensure that your illuminator beam matches your camera FOV in both ONLY THINKING ABOUT THE CAMERA distance and width. Some illuminators have adjustments By the very defnition of feld of view that we explored in the where you can make the beam narrow and long, or wide and f rst paragraph, it would seem odd to think about anything short. Others have a f xed light pattern. In almost all cases, the other than the camera. But in fact, one major mistake in set- resulting FOV that matches the illuminator's capability will be a substantially shorter distance than what can be achieved with the camera alone in full daylight conditions. Not taking the FOV of your illuminant into consideration can be a costly mistake in terms of coverage. You'll need to stay up late to ensure these coverages match, but make sure you also consider the FOV of your illuminant during the planning phases, or you could end up with gaps in your nighttime coverage. 4. 5. NOT UNDERSTANDING PIXEL DILUTION The "rule of thirds" applies when you are taking vacation photographs, but it does not apply when aligning security cameras. Plan to only allow 10% of the view to be above the horizon line. 142 / SECURITYSALES.COM / SEPTEMBER 2013 Pixel dilution is the idea that the more information that is attempted to be represented by an individual pixel, the more diluted that information becomes. Tis issue typically arises when setting up a scene and opening up the camera's FOV so it is as wide as can be accommodated by the lens. It's available information, so why shouldn't we widen the lens to capture it? Te answer is … it depends.