How to Illuminate Stained Glass Windows

I am a lighting designer and I love what I get to do every day. We work on all types of projects from large hotels or high rises to boutique retail shops. I enjoy them all. I have learned over the years that even small projects can have unique, creative challenges.

This is especially true with projects that require backlighting of stained glass. We often have these opportunities. The one consistent truth about illuminating stained glass is that they are each a unique application. The best lighting solution for one probably isn’t the best for the next. The window size, shape, location, and color saturation all must be considered.

On a recent project, known to us as the Rose Window project, all these considerations were applied. The Rose Window is a large, round stained-glass window that measures 10 feet in diameter. The window is the main focal point behind the altar and contains rich blue and red glass panels that show gloriously on Sunday mornings.

We were tasked with replicating that appearance on the window for evening worship services. Let me first make clear that sunlight is the perfect light source. It contains every color in the visible spectrum and is therefore impossible to replicate with complete accuracy with man-made light sources. 

The one thing I have learned in my career is that illuminating deep saturated stained glass always takes more lumen output than you might first think. Before calling us, the church mounted a single LED fixture on the roof behind the window that produced 8500 lumens and it didn’t provide enough illumination on the window. 

We began by modeling the window in our lighting software and experimented with controlled beam fixtures that utilized a variety of beam spreads and intensities. In the end, we selected three luminaires to illuminate the window. Each 5000K luminaire produced approximately 24,000 lumens. We placed the luminaires 10 feet from the window. The center luminaire utilized a 12° x 38° and the two outside luminaires utilized a 23° beam. This design provided approximately 1000 footcandles to the center of the window and an average of just under 700 footcandles.

Our client is happy with the result, which means we are too. Final images are shown below.