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Single-color LEDs provide the most cost effective way to mix color, but you have multi-colored shadows.
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Ford Sellers is the Senior Product Development Manager for Chauvet Professional, and Iluminarc.
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LEDs using COB (Chip-On-Board) Technology have the advantage of having what appears to be a single source, so they can appear to cast a single shadow rather than a multi-colored one.
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Quad-color LED's still produce shadows, but they don't look like the rainbow. They're just looks a little softer.
By now, just about everyone is familiar with the advantages of LED lighting fixtures, from their lower power draw and heat emission to their extended life and silent color changing – an attribute that's especially important during church services! Yet, nothing in life is perfect, and that includes LED technology.
Along with their many benefits, LED fixtures can present a challenge when it comes to dealing with their chromatic (aka multi-colored) shadows. As the name implies, these shadows are formed when the light from different LEDs in a fixture makes it past the object that's being illuminated to cast a colored tint around the edge of its shadow.
As LED technology has progressed over the past decade, manufacturers have come up with different solutions for dealing with chromatic shadows, including multi-dye LEDs and more recently COB (Chip On Board) fixtures. Each of these solutions has its advantages and drawbacks, which means that there is no one alternative that's best for every church.
Before selecting LED fixtures for your church you should be aware of how they create colors and what impact this will have on producing chromatic shadows – but that's only the beginning.
You'll also want to consider how far the object being illuminated will be from the fixture. (If the illuminated object is a great distance from the fixture, the question of color shadows is far less important.) Then there's the question of silence; a fixture that produces no color shadows may not be quiet enough for your live or broadcast services. As always… you'll also need to weigh these factors against the demands of your lighting budget.
Creating Colors (And Shadows)
When LED washes first came on the scene about 10 years ago, colors were created by mixing three primary hues using dozens of separate red, green and blue LEDs. These fixtures had multiple LEDs in each color dispersed evenly across the front to make the color as homogenous as possible.
However, when you look directly at the front of the fixture, you see each different LED. This led some people to joke that the front of one of these fixtures looks like a bowl of Skittles.
In theory, this “Skittles technique” works well to create colors when you're lighting a smooth surfaced object. However, when you're lighting something like a choir or a three-dimensional object like a pulpit, the surfaces aren't flat. In these cases, the object or person being lit will cast a shadow… or more accurately one shadow for each LED light source on the front of the fixture.
When these shadows all overlap, you'll get a standard black shadow. But at the edges of the shadow, you may have some points where only the red and blue LEDs are blocked, and a little bit of green and amber makes it past the target to give the shadow a greenish amber tint. In some cases, each point along the edge of the target will block different LEDs, to create a rainbow-like shadow.
This effect is exaggerated at tighter beam angles, with greater distance between the LEDs on the fixture, and the closer the illuminated object is to the fixture. If the object is far from the fixture, the angles that different sources hit the target at will be very similar, so chromatic shadows are minimized.
The Inside Story
A few years ago, manufacturers began to address the issue of chromatic shadows by coming up with technology that mixes colors inside the fixture. This is accomplished by placing a lens over a single chip that contains multiple colors of LEDs. The beam angle of the individual colors is very wide (usually 120 degrees), so that the color all bounces around inside the lens, and blends fully before leaving the front of the lens, hence color shadowing is minimized.
This technology uses multi-dye (multi-color) LEDs, with a lensing technology called Total Internal Reflection, or TIR. It is common to see units using Tri-color (RGB), Quad-color (RGBW, or RGBA), and even Hex-Color (RGBWA+UV) LEDs. One advantage of multi-dye LEDs is that you can achieve very narrow beam angles, for tight beams, or longer throw applications. Another great advantage of using multi-dye LEDs is that the technology is easily scalable. This means that a manufacturer can more easily design a series of fixtures with seven, 12, and 19 Quad-color LEDs, to be able to fit a large variety of applications.
These units still use multiple LEDs, but they can be spread across a larger heat sink. This means that you can make them bright, by adding more LEDs, but you may still have multiple shadows. However, since each lens on the front of the light is transmitting the same color, the shadow does not look like a rainbow -- it just looks a little softer.
COB Technology
More recently, manufacturers came up with a second way to address the issue of chromatic shadows. This technology is called Chip on Board, or COB, for short. It works by combining a large number (as many as hundreds) of
microscopic single-color LEDs on a “big chip.” The cooling of these big collections of LEDs is very difficult, so primary heat sink is made as a part of the LED board.
Once light is generated by these LEDs, it is either directed with a lens, a reflector, or both, for longer throw distances. Using a reflector instead of a lens further improves the color mixing. Fixtures using a single COB have the advantage of having what appears to be a single source, so they can appear to cast a single shadow rather than a multi-colored one.
Another great advantage of using COBs with reflectors is that the light source looks much more natural. Color mixing in COBs can be done several ways. The easiest way is to arrange the colors in tiny stripes. This does not eliminate the colored shadow problem, however, because the majority of each color is still coming from slightly different angles. The color separation is accentuated in fixtures that use a lens to narrow the beam angle. To improve upon this, some units arrange the individual colors in a checkerboard style pattern. This is much better at blending the color, but it's also a more expensive chip design.
Since the small LEDs inside a COB fixture generate more heat, they require a cooling fan. This creates some noise, which is something to consider if you require silent operation in your lighting.
So, as you can see, there is no one-size-fits-all-churches solution when it comes to color shadows. Each approach to color mixing has trade-offs. Single-color LEDs provide the most cost effective way to mix color, but you have multi-colored shadows. Multi-dye LEDs minimize chromatic shadowing, but still use multiple sources. COB units can have the best color mixing, and look the most like a traditional light source, but are difficult to produce at narrower beam angles, and can need fans to cool, which may make noise.
The best course of action is to work with a trusted lighting professional or dealer and detail how you are going to use color-mixing fixtures. Will they be used at live services only or for broadcast too, where silence is critical? How far will you be throwing light and at what beam angle? Once you've answered these questions, you can test drive the fixtures, and see the difference with the only tool that really matters…your own eyes.
