How much light? Outdoor lighting designers hold to the maxim that “less is more.” Homeowners are concerned with security, safety, and utility. A good design, professionally installed and maintained, fully addresses these practical concerns while knocking everyone’s socks off with stunning aesthetics.
Beauty, safety, security, and practicality seem at first blush like conflicting demands. After all, isn’t as much light as possible the best deterrent to burglars and vandals? Isn’t safety best ( and potential liability least) with light as bright as day? And won’t the property be an eyesore lit up at night like a refinery?
If light came in cans, like soup, and all cans were the same, all that would be true. But light is more complicated than that.
First, there’s a difference between luminance and brightness. The luminance of a light source can be measured by a machine in units of candela or lumens, and the result will be the same as long as the source operates consistently. Brightness is a human perception. A person can judge two identical light sources to have very different levels of brightness. The perception of brightness depends on things like the contrast between a light source and what’s around it, and on the state of the person’s pupils when looking at the source. A bulb seen against a bright background appears less bright than when it’s seen against a dark background, and that same bulb appears dimmer or brighter depending on what the person was looking at previously.
And then, there’s a light source’s color temperature, a crucial ingredient in a lighting design’s visual appeal. An incandescent bulb, producing light by heating a metal filament, is as hot to the touch as it looks. An LED, in contrast, can provide the same luminance (measured in lumens) as that incandescent, but is cool to the touch and can look cooler, or look warmer than the incandescent, according to its color. LED color temperature is rated as Correlated Color Temperature (CCT) as degrees Kelvin.
Landscape lighting design is a lot more involved than it seems to many, as illustrated by this introduction to some of the underlying physics and perceptual complexities a designer’s skill set and experience are grounded in. An understanding of visual paths and destinations, for example, helps keep eyes adapted to brighter lighting from awkward transitions to softly lit areas, which in turn allows for realization of the “less is more” principle.
There’s more a pro works with, much more. Factors like specularity, diffusion, reflectance values, and glare, among others. These are the things that make the difference between a good outdoor lighting design and a great one. You see, there’s more to it than meets the eye.