No-Spill Spotlight

I call this my “Judy Garland” project. Even though I’m a gay guy, I was initially not a Judy Garland fan. After a few years of seeing her work, I’m at the point where I can say, “Hrm, she was really something…” So this project is inspired by Judy. Singing her heart out in a spotlight.


“Spill” is a term in lighting engineering for the unwanted extra illumination that carries over to parts of the scene. Using the picture above, I would like to develop a spotlight that lights up Judy and not the large circle on the floor. My dream is to have it be able to track and light an actor dynamically as they move around the stage, even if other actors are present.


Simple steps:

  • Subtraction from a static background

This is the easiest idea. The program saves a “static” image of the scene. For example, a picture of the stage without any actors on it. Then, the algorithm simply lights up anything that is different than the static scene

  • Subtraction from a background over time

A little trickier. Basically, “light anything that moves”. If an object stays unmoving for more than a few seconds, it becomes part of the static background

  • Dynamic outline recognition

The final objective. An object in the scene is chosen, and the algorithm finds the boundary of the object and lights it up, even as it moves. For example, the spotlight can
“flash” for a second that would be unseen by the human eye, but the algorithm could get a glimpse of any background revealed behind a moving actor. Plus, the boundary could grow and shrink very quickly to create a dynamic changing outline.


I was excited about this “Lightform” light projector that can highlight parts of a scene. I don’t think it works dynamically for moving objects, but for $699, it’s a fun idea for Halloween or art projects as “augmented reality”.

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