5 Best Practices for Using a Lightboard in Instructional Videos
A lightboard is a teaching aid specifically intended for instructional video production. It is an edge-lit sheet of glass held in a frame standing between the teacher and the camera, with the video horizontally flipped. The teacher writes on the glass with fluorescent dry-erase markers so that the text or drawings appear floating in mid-air. Because the interior of the glass is flooded with light, the camera-facing surface of ink glows brightly. Lightboards are close analogues to the chalkboards and whiteboards that are familiar to any veteran teacher but are tailored for the one-on-one microlecture format in that the teacher need not turn away from the student to write or reference a diagram. Over the past half-decade, lightboards have exploded in popularity: Many universities and community colleges have built lightboard studios, and millions subscribe to YouTube channels featuring lightboard videos.
I’ve built lightboards at both extremes of lightboard design. The first is quite faithful to the original open-sourced design of its inventor, Michael Peshkin: The frame is constructed of steel, and the glass is a custom-ordered 4'x8' sheet of low-iron glass with holes cast into it for mounting to standoffs on the frame. Low-iron architectural glass is critical: Regular “clear” glass will glow green when edge-lit due to the higher iron content. I made mistakes with that design. Instead of basing the glass’ aspect ratio on standard chalkboard sizes, it would have been prudent to reference the camera’s frame size instead and design around a 16:9 proportioned piece of glass to minimize unusable areas of the board where the teacher’s drawing would be outside what the camera can see. I also built the frame with a fixed height, meaning that it would be difficult for a teacher in a wheelchair or a very tall teacher to use.
At the other extreme, my latest lightboard was built for under $200 with materials sourced from a local big-box hardware store: simple construction lumber, a sheet of acrylic, and a spool of under-counter LED strip lights. The architectural glass is far superior to the acrylic in clarity and durability, but the acrylic is much lighter and cheaper—this model can be comfortably lifted off the floor and set on a table by a person of average strength. A sheet of 3'x6' acrylic costs between $70 and $150, depending on the thickness. I went with the thinner, cheaper option, since acrylic is soft and prone to scratching. Any scratch will catch the edge-lighting, fluoresce, and require replacement. That’s less than 10% the cost of the cheapest low-iron glass at that size available.
Here are a few best practices I’ve picked up over the years:
- My admiration for the OBS (Open Broadcaster Software) Studio project began after successfully experimenting with how it worked for lightboard recording. It can flip the frames, chromakey the background from a slideshow to lay over the camera layer, and record or live stream high-quality video. Use it.
- If using overlaid visual aids, arrange their layout to make sense with the confidence monitors the teachers can look at to see the composited output from OBS. If they’re looking at the confidence monitor, it should appear to the students that they’re looking at the content being superimposed over the camera layer.
- There will always be some portion of the board that is outside the camera’s frame. Use a dry-erase marker that matches your backdrop color to indicate the usable region for the teacher. If the camera is bumped, the marks will usually disappear into the background.
- Eliminating reflections on the glass is a challenge. Use a polarization filter to remove most of the reflection and blackout drapes for the rest.
- If a lecture requires frequently redrawing a portion of a figure (graph axes, for example), draw the static portion on the camera side of the glass and draw the varying portion of the figure on the usual side. When you wipe off the teacher’s side of the glass, the static part of the figure remains exactly where it should be for seamless editing.
[This article appears in the September 2019 issue of Streaming Media Magazine as "Drawing on the Lightboard."]
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