Tag Archives: light stick

Building a light stick

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Following my attendance at a London Photographic light painting workshop, I decided that I wanted to build myself a light stick, suitable for producing light trails and more. This is basically an approx 1m long strip of wood, with leds running down the side. You can’t buy them off the shelf, but the constituent parts are all readily available from eBay.

The Parts

At its heart, the light stick is just a strip of 5050 spec SMD (surface mount device) RGB LEDs, with a density of 30 LEDs per metre. These strips actually have 3 LEDs at each location, one red, one green, one blue.

Don’t be tempted by the alternate 3528 spec SMD strips, since these produce a much dimmer light. The LED strips are produced to a variety of weather proof standards, with the IP65 rating being the most suitable for building light sticks, since it encases just the top of the LED strip in what appears to be a translucent silicone sealant. The RGB LED strips usually come with a IR remote control device, with either 24 or 44 keys, which allow for choice of constant light colours, or various transition effects between colours. I purchased a 5m long reel from eBay which had a 24 key IR remote. The strips can be safely cut every 10cm, so if you can source additional IR receiver units, one reel can be used to build multiple light sticks

The 5050 LED strips require a 12volt power source, usually from a small mains AD/DC adapter. This isn’t much use for light painting which is going to take place outside, far away from any mains source. The solution is to just use a set of 8x AA batteries wired in series to get to the 12v mark. Again I turned to eBay to purchase a simple 8 battery holder. The battery pack has a PP3 connector, so another trip to eBay obtained a PP3 terminated cable.

For the stick itself, I made a trip to a local DIY store to pick up a length of wood measuring approx 2cm by 4cm, and some cable clips.

The Assembly

With the parts obtained, it was onto assembly of the light stick. The first step is deciding how long a stick to make. The LEDs come in a minimum of 5m lengths, which have explicit markings for where they can be safely cut every 3 LEDs (approx 10 cms). I decided to make a 90cm long light stick, giving 27 LEDs in total. I first cut the LEDs to the right length, used them to measure the exact same length for the stick, and then cut it to size.

The LEDs come with an adhesive backing tape, so they can be stuck directly to the narrow side of the wooden stick with minimum of fuss. With that done, the next step was to attach the IR receiver unit to the wider side of the stick and fasten the cables with a few cable clips.

The only remotely difficult step is connecting the battery cable to the IR receiver power cable. To do this I stripped the insulation off a 1 cm length of each cable, then simply soldered the two cables together. I used a short piece of heat-shrink to cover the solder joint and then wrapped the whole cable in layers of red insulation tape to make it a nice & robust.

The only unsatisfactory part of the exercise, was attaching the battery pack to the stick. With the shape of the battery pack I had purchased, there was no effective way to permanently connect it to the stick without making it impossible to later remove the batteries for recharging. In the end I went for the high tech approach of using 2 elastic bands.

The image above shows the finished product. For reasons of weight distribution, the battery pack is located 1/2 way along the stick, directly in its center, though you can’t see that in the above picture since I cropped out the boring 1/2 of the stick. The white box is the control unit for the LEDs, the power supply cable pluging in on the left hand side of the unit. On the right hand side, the top cable with the black terminated end is the IR receiver sensor, while the other cable takes power to the LED strip itself. The coloured buttons on the remote control, self-evidently, map to the desired colour of the LEDs. The other buttons control brightness, on/off and 4 different colour fading patterns.

The Demo

Only completing the device on Sunday evening, I have not yet had an opportunity to go outside and try it in the real world. I did however, do a very quick test inside to see how well it handled. Based on this test I decided that using a remote control isn’t the most convenient thing. It would be better to have a simple on/off switch directly on the light stick. By simple I mean, I attached the remote control to the stick using another elastic band, pointing at the IR sensor :-)

London Photographic Light Painting Workshop

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Through the London Photographic Meetup group I’ve been to many different photographic workshops, learning a great deal. Over the past couple of years, the group has had quite a strong focus on lighting related workshops, covering various aspects of studio lighting & off-camera flash. It was one of the off-camera flash workshops, 3 years or so back, that motivated me to create the Entangle Photo application for Linux desktop users.

The workshop that I’ve long wanted to attend, but never had the chance to, is their “Light Painting” one. Last week I finally got the opportunity and was not disappointed. The location varies from event to event, with this particular workshop taking place in Green Park. We started out in a cafe where the organizers described the various pieces of equipment we’d be using. There were basically two devices, a light string (a long cable with a bundle of 30 leds on its end) and a light stick (a ~1m long piece of wood with an led every ~3cm). Neither are things you can buy pre-built in the shops – the London Photographic organizers home-build them all from electronics purchased on eBay.

Setup

The weather was a bit on the iffy side, so we started out with umbrellas being held over our cameras, but we didn’t let that put us off the evening’s activities. In any case, the rain had pretty much stopped after the first 30 minutes of the session. The plus side was that the rain made the ground reflect a little more of the light. As might be expected, the exposures are on the long side, with the iso/aperture dialled in to achieve the desired ambient illumination, while still allowing on the order of a 1 minute shutter opening to give time to produce the light effects. Needless to say, the cameras were on tripods and shutters triggered using cable release. With such long shutter speeds, we’re shooting in “bulb” mode with someone counting time on a stopwatch.

Light orbs

The first effect attempted was to produce basic light orbs. These are achieved using the light strings, by swinging the string in a circular motion in front of your person, while slowly rotating your feet through 180 degrees. Done correctly this results in an attractive orb shape

Light tunnels

Another effect that can be produced using the light strings, are tunnels / tubes of light. The starting premise is much he same as for the light orbs, simply swinging the string in a circular motion in front of your person. Instead of rotating on the spot though, you slowly walk forward / around the scene.

Light trails

Following on from the basic light orbs, the organizers got out the light sticks. The light sticks have fancy controllers for choosing between a range of different colours, or even strobing through the colours in a sequence. The technique is simplicity itself, simply turn on the light stick and walk it around the scene. The key is to keep your motion of the stick fluid, to avoid jagged edges on the light trails.

The Peacock

As mentioned above, smooth movement of the light stick is key to getting continuous light trails. For the next trick, the goal was to produce perfect circles of light. Acceptable results cannot be achieved by hand-holding the light stick, so the trick here was to put a bolt through one end of the light stick, and then fasten this to a tripod head in some manner. The light stick can now be smoothly rotated through 360 degrees, producing perfect circles of light, which I’ve named “The Peacock”

The Brain Orb

The final technique of the night was the most difficult and time consuming. This involved a long pole, with a bundle of leds on its end. Kneeling in one spot, the goal is to trace out a sequence of hoops gradually building up the doom pattern, which our organizers nick-named “The Brain Orb”, though it reminds me of an igloo.

Parting thoughts

The general aim of the workshop was for the organizers to demonstrate the techniques above so that we, as photographers, understood how to achieve the various different light painting effects. The workshop lasted several hours, late into the evening, but even with the small group (~15 photographers) there wasn’t time for us to try out every technique ourselves. The idea is that after completing the workshop we’d have the knowledge required to go off and put the techniques into practice ourselves. I’m certainly intending to do some experimentation in this area myself. The organizers themselves did a great job at running the event & getting through the material. If anyone reading this is interested in light painting, and based in London, it is well worth keeping your eyes open for future repeats of the light painting workshop (won’t be until autumn time though, due to need for dark evenings!).

One idea I had to improve the results from “The Peacock” technique is to bring in an off camera flash. The camera settings are dialled in to expose for the ambient, while giving plenty of time for the light painting technique. What we can’t do with this, is get a nice exposure of the subject’s face. By adding in a low power pop of off-camera flash at the end of the exposure, we could nicely bring out the features in the subject’s face.