One of the most common challenges we face when replacing halogen lights with LEDs is the increased shadowing LEDs can create. Visual directors will often comment that what before were “soft shadows” have become “dark shadows” under LEDs. The criticism is fair. Increased contrast between the lit and unlit sides of a rack, garment, or piece of furniture are a potentially nasty by-product of a directional (flood and spot bulb) LED retrofit. Here’s where the issue comes from, and how we address it.
The reason the shadows are softer under incandescent light is an effect we might call “halogen haze.” While every directional light bulb has a specified beam, say 25 degrees for a narrow flood, some of the light cast will fall outside that beam. This “spill” light ricochets around the room, meaning that the target object will be hit by light sent not only from the bulbs, but from the ceilings, walls, pillars, etc. The target product therefore, becomes visually flattened by the all-encompassing luminary haze. An illustration:
LEDs, by contrast, spill much less light—10% of total light is spill, compared to 40% in halogen lighting. The new bulb, guiding a significantly higher portion of its light directly to the target, results in a sharper shadow:
The lighting solution:
1. Increase the number of light sources, and space them evenly. Relamping (increasing the number of bulbs) by as little as 30% of total count can almost entirely eliminate a perceived increase in shadowing. The second important step is de-clumping. Not a real term, this is a reference to insuring that fixtures are no longer clustered together. With LEDs' increased capacity for delivering candelas to a target, fewer lamps are required per target; clumping will only worsen the shadowing issue.
2. Make product adjustments. Some LED light bulb companies pride themselves on sharp contrast between brightness and shadow in display environments. Given that this is sometimes strongly at odds with the client's sensibility of "good" lighting, we have identified a set of directional products which offer a softer cast—we can maintain color quality and detail while reducing the shadow-related shock value of an installation.
3. Then there is education. Visual and design professionals, ever more familiar with LED products, are beginning to appreciate that when you increase the amount of light that strikes an opaque product, the contrast of the resulting shadow inevitably increases. If you want more light to strike a piece, math dictates that the area behind the piece becomes relatively darker. We endeavor to be part of this education process with every project we do, minimizing the lighting problems where possible.
We leave you with a nice before-and-after of an antique cabinet and the massive positive impact directional LED lighting had over halogen lights. The benefits outweigh some shadowing.
Hungry for more?
We use this space to air thoughts on the industries in which we take part: LED lighting, aesthetic commercial lighting, and the growing industry of LED lighting as a service.
Wavelength is proud to be part of a community that includes offices, hotels, schools, retailers, LED manufacturers, and energy project investors. Material published here, however, reflects only our personal views on lighting, not those of our various partners.