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May 2012

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How’d They Do That? Colonial Baptist Church, Cary, N.C.

Church improves its lighting by eliminating nearly half the fixtures.

by Jim Kumorek

When it comes to lighting, I have a lot of experience programming cues for services or events, and have hung lights to augment an existing lighting plot, but have never actually created a lighting plot from scratch. So when Colonial Baptist Church in Cary, N.C., asked for some help with their choir lighting, I was excited about applying some lighting plot theory.

The issue we were trying to solve was spotty lighting throughout the loft area. It was fairly obvious from the naked eye, but on video the variation was really obvious. Over the years the church's volunteer team tried to even out the lighting by adding more fixtures and pointing them at the darker spots, but they never ended up with a good solution.

On inspection, the problem seemed fairly apparent. The throw distance is extremely short-about 15 feet-and most of the fixtures had medium flood lenses in them, which would put out a very small beam at that distance. My original thought was to do two-point front lighting for each section of choir loft, but after discussing this with my friend, lighting designer Greg Persinger, he convinced me that one-point lighting would work well in this context.

We took measurements of the choir loft and the required throw distance. Almost all of the fixtures available for use were ETC Source Four PARs, so I went to ETC's website and pulled the spec sheet for the fixture, which includes photometric data on different available lenses.

For any light fixture, there are two specs of interest: the beam angle and the field angle. The field angle extends to where the outside edge of the beam is at 10% of the intensity of the center of the beam. The beam angle extends to where the outside edge of the beam is at 50% of the center.

From doing a little research on the web, the consensus is that for even coverage, the beam fields should touch, with the fields overlapping.

For the existing medium flood lenses already on most of the fixtures, the beam width is 22% of the throw distance for the beam width, and 32% for the beam height. With the 15-foot throw distance, this results in a beam shape of 4.9 feet by 3.4 feet-clearly, way too small.

Applying the appropriate factors for the wide flood lens, the beam field would be 7 by 4.5 feet. Given the shape of the choir loft, this was also too small.

I pulled up the specs for the optional extra-wide flood lens, and this lens would provide a beam spread of 8.8 by 8.8 feet. Not perfect, but the best we could manage. We ordered 16 of these lenses with the goal of covering the choir loft with six fixtures (48 feet divided by 8.8-foot beam spread).

With the help of the church's Technical Director, Eric Myers, and lighting team volunteers Amy Justice and Cindy Stephenson, we starting changing out lenses, removing extra fixtures, and spacing out the fixtures as planned. After we had a few up, we used a light meter (a CEM DT-1308) to check for evenness, and did a quick visual check to see our progress using actual faces.

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Jim Kumorek is the owner of Spreading Flames Media, providing video/media production and writing services to the A/V/L, technology, architectural and hospitality industries. He has led audio, video and lighting teams in churches as both staff and a volunteer for over 10 years. He can be contacted at james@spreadingflamesmedia.com.