- #1
PhilR
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- TL;DR Summary
- I'm looking for some advice on a hobby project which aims to retrofit LED emitters into theatrical lighting devices which previously used gas discharge light sources.
Hello!
I should preface this by saying that I work in the film industry where we use lots of different lighting devices, but this is not a commercial project. It's a hobby effort to help a bunch of slightly-used equipment avoid becoming e-waste. Not sure if this is high school, undergrad or advanced, really.
Some of our lighting devices gas discharge light sources (see "MSR," "HMI"). They form beams from these sources, often using a pair of plano-convex condenser lenses near the source and then two more lenses near the output, the final one being adjustable for focus. Between those two lens groups tends to be a selection of devices intended to create effects in the beam, particularly cut metal shapes which will be projected, colour filters, etc.
See image of a typical setup here; reflector is at right, the bulb itself is missing, the two condensers are visible. To the left is a wheel of circular glass colour filters which can be rotated into the beam. See image of the sort of results we are going for here.
There is a general desire to move away from using gas discharge lights for this. LED is lightweight, robust, somewhat more efficient, easier to control, and does not use mercury. The problem is that simply removing the arc light and replacing it with an LED does not work very well. The LED is a much physically larger light source. The whole thing ends up being very inefficient with a lot of light falling outside the originally designed optical path, and it projects a larger image than is really desired.
Is this a problem I can plausibly solve with by retrofitting a different optical arrangement? It ideally needs to be something I can do with parts I can purchase. Unfortunately I'm only vaguely aware of the function and behaviour of condenser lenses and I'm not sure if what I want to do is practical.
Not really sure where to start with this so any advice greatly appreciated. More than happy to do the hard work myself if this is something I could teach myself to do. I've looked at things like this, but it's all going a bit over my head in terms of how I should approach the problem I describe.
I should preface this by saying that I work in the film industry where we use lots of different lighting devices, but this is not a commercial project. It's a hobby effort to help a bunch of slightly-used equipment avoid becoming e-waste. Not sure if this is high school, undergrad or advanced, really.
Some of our lighting devices gas discharge light sources (see "MSR," "HMI"). They form beams from these sources, often using a pair of plano-convex condenser lenses near the source and then two more lenses near the output, the final one being adjustable for focus. Between those two lens groups tends to be a selection of devices intended to create effects in the beam, particularly cut metal shapes which will be projected, colour filters, etc.
See image of a typical setup here; reflector is at right, the bulb itself is missing, the two condensers are visible. To the left is a wheel of circular glass colour filters which can be rotated into the beam. See image of the sort of results we are going for here.
There is a general desire to move away from using gas discharge lights for this. LED is lightweight, robust, somewhat more efficient, easier to control, and does not use mercury. The problem is that simply removing the arc light and replacing it with an LED does not work very well. The LED is a much physically larger light source. The whole thing ends up being very inefficient with a lot of light falling outside the originally designed optical path, and it projects a larger image than is really desired.
Is this a problem I can plausibly solve with by retrofitting a different optical arrangement? It ideally needs to be something I can do with parts I can purchase. Unfortunately I'm only vaguely aware of the function and behaviour of condenser lenses and I'm not sure if what I want to do is practical.
Not really sure where to start with this so any advice greatly appreciated. More than happy to do the hard work myself if this is something I could teach myself to do. I've looked at things like this, but it's all going a bit over my head in terms of how I should approach the problem I describe.