Category: Teaching Ideas

making a lightboard

13/4/2021

Instructional videos, especially those that involve writing on a board or screen, are easy to produce for educators. This is especially true for mathematics and physical science courses where equations need to be explained.
A common way is to simply set up a camera towards a blackboard or white board and simply record yourself writing and speaking.
Although quite basic technically, this method suffers in that you aren’t actually looking at the camera when you are doing the writing.
Another method, employed by a number of educational channels is to write on a screen/computer and then record this. You hear the presenter, but don’t see them, as you see the writing on the screen.
However, there no “human” evidence, either the hand writing, or the person talking.
There is some research on the efficacy of this instructional method and the presence of a hand, or better still, the presenter, leads to improved engagement and therefore retention of content.
It’s this reason why a number of presenters simply film their writing on paper from above as a way of communicating.
One alternative method involves the use of a light board and it’s the way I have been producing content where I simply need to “instruct as I write”.

The concept is fairly simple, though has a little more preparation required.
The presenter writes on glass with a fluorescent whiteboard marker with the camera on the other side of the glass. This way the presenter is looking straight at the camera whilst writing.

Of course, you will ask, do you have to write in reverse? No you don’t, you simply write normally, but to address the reversed image, when you edit the video, you flip the video horizontally. So now it’s the correct way round, and if you are right handed, you’ll appear left handed!

My rough and ready effort. Clearly I am not a designer, but it works just fine.
Obviously not where I use it!

There are a few things to consider.

The light board. In essence it’s a glass pane that you right on. The writing is lit up due to a strip of leds attached to the edge of the glass.
You can purchase a lightboard separately (and they're not cheap), or you can make one.
There are lots of diy examples online (just google diy lightboard). I made mine out of an old poster frame, but be mindful that type of glass is usually 3mm and a little more fragile than getting some 5mm safety glass instead. Bigger is better in one sense (more to write but be mindful it will get heavy and you need to ensure with your camera that the backdrop extends all the way to the edges
Avoid using polycarbonate/perspex. It scratches too easily and is much harder to clean
The lighting - soft diffuse lighting is best. I use two softboxes either side. A top light isn't essential. But if you want things cheap, play around with adjustable desk lamps
Fluoro dry eraser markers work best. Definitely not black
The backdrop - needs to be completely black. I use black cloth but I have also used a large foldable black scrim as well
Camera - any camera will do but ideally will have manual adjustment. AUTO will make the backdrop visible and the writing will be blown. Dont use too much of a wide angle as that will. impact how much backdrop you need. Prefocus on the writing and set to manual otherwise the camera searches focus. Ideally also a smaller aperture to give better depth of field so you are in focus too
Audio - the glass will muffle your speech so you could use a shotgun microphone that you will need to connect to your camera via extension cord
I use a lav and I love my Røde iPhone lav mic. It connects directly to my iPhone and record on it and I then transfer the audio to my video editing software
Editing - you will need to crop and flip the video so the ball goes to the screen. increase the contrast so that any smudges to light spills are no longer visible. I usually increase vibrance/saturation to make the writing stand out

Other tips

Make sure there is no writing on your shirt and plain. I do have physics t-shirts but I purposely designed them to be reversed so they look correct on the videos
No bright windows behind the came or anything bright for that matter as the reflection will be picked up on the glass
Have lots of old towels/wipes to rub off the markers. They will get dirty quickly (especially if you make mistakes) and dirty onles will smudge the glass. Keep some window cleaner close by but I only use this at the very end

Some links

Here is a good link to read more. Says similar tips but also has links to ideas
Paper from International Designs of Learning
Paper from Peter Rogers, Ph.D., PE Georgia Southern University Using Lightboard Video Lectures to Improve Student Learning ...https://peer.asee.org › using-lightboard-video-lect...

0 Comments

Understanding measurement

16/8/2020

1 Comment

or A LESSON UNITS, UNCERTAINTY AND SIGNIFICANT FIGURES

I find students when they start a physics course, have a weak understanding of how measurement works and how values are discussed, and so I cover key concepts of units, uncertainty and quoting of significant figures, before I start the physics course proper.
What follows is a an activity I do with the students over the course of 1-2 hours.
(I include some thoughts in red)

Determining the Density of a pice of paper

Divide your class into groups of 3
Give each group a single sheet of A4 (or 'letter') sheet of paper and ask the to determine its density as accurately as possible.
Give as little instructions possible but provide them only a meter ruler and access to a set of digital scales.

Finding the length and width is relatively straight forward, but the thickness is another matter.
I find the students generally fall into two camps, they either fold the paper multiple times to ge a thicker section (which has its limitations) or they ask for a stack of paper and measure that (again, the size of the stack contributes to uncertainty)

Once they determine the dimensions and the mass, and thus calculate density, get them to write their answer on the board.

When I survey their responses, most get similar 'numbers', however, there will be some with different units (I insist on them quoting units) and many over quote significant figures.
So as I discuss the results in the class I ask
"Are these results the same?"
To the ones who over quote numbers, I ask "how confident are you of those number?"
I then ask about the thickness measurements, "How certain are you about the number being that precise value?"
This then all leads to a discussion on
- talking the same 'language' - SI units
- how we express our uncertainties
- the role of significant figures (check out my video here)

At this point , teach the points measured above, including how to express uncertainties

Once you have covered the concepts , get students to repeat the task, but prior, teach them how to use a micrometer.
Students now need to determine the density, using same units, and quoting with % error and in correct significant figures.

When results are compared on the board, all their results should fall within the uncertainty of the over the results (hopefully :) ). This could be graphed to make it more clear.

Feel free to provide feedback below and any modifications you tried

1 Comment

PhysicsHigh blog

making a lightboard

Understanding measurement

or A LESSON UNITS, UNCERTAINTY AND SIGNIFICANT FIGURES

Author

Archives

Categories

Support