When giving a presentation to a diverse audience (e.g. of experts and non-experts, or of employees from two different departments in a company), you have a problem: you can only make one set of slides, but sometimes you might want to tailor different parts of the presentation to a different audience.
For example, one might want to give a presentation at an easily-understood overview level while also providing technical details for any domain experts in attendance.
Nearly all projectors and screens consist of three light-generating elements, in red (1), green (2), and blue (3).
By giving some members of the audience a pair of green-lens glasses (which block all red and blue light), we would be able to hide certain elements of the presentation that were not relevant to the green-glasses wearers. We can use a set of red-lens glasses and blue-lens glasses in the same way (see Figure 1).
With this technique, we can show up to three entirely different slide presentations, with the only limitation being that each presentation must consist of only monochromatic images.
- Red glasses can see the following colors: red, yellow, magenta, white [*].
- Green glasses can see the following colors: green, yellow, cyan, white.
- Blue glasses can see the following four colors: blue, magenta, cyan, white.
[*] Note that this is “additive” color space (where red + green = yellow), not the “subtractive” color space one might be familiar with from mixing paints.
Fig. 1: These glasses block certain wavelengths of light. By carefully constructing our slide decks, we can use these glasses to give up to three different presentations to the same audience at the same time.
So a slide that should be visible to everyone in the audience should be white (or shades of gray). Whereas if you only wanted to present to the red & green glasses-wearers (but not the blue ones), that text would be yellow. See Figure 2 for an example.
Fig. 2: A sample presentation that is meant to provide both “optimistic” conclusions (green glasses) and “realistic” conclusions (red glasses). This is what the presentation looks like with no color-filtering glasses on.
Fig. 3: The presentation from Figure 2 in “pessimistic / realistic” mode, as viewed through red lenses. All of the green text has disappeared!
Fig. 4: The presentation from Figure 2 in “optimistic” mode, viewed through green lenses. Red text has disappeared.
Fig. 5: Real-world demonstration: a color-enhanced version of what a red-blue version of this presentation looks like through red-blue “3D” glasses. The effect is almost 100% convincing for the human eye, but the camera actually manages to pick up a lot of the non-lens color, so this photo has been edited to more accurately reflect the perceived image.
A superior (but more logistically difficult) implementation:
It would also be possible to implement this same system with polarized glasses (as were used for some 3D TVs in the early-to-mid 2010s).
This would have the advantage of providing full color, but the disadvantage of not being compatible with a standard conference room projector. Additionally, you would be limited to two different presentations, rather than 3.
PROS: Improves your presentations by letting you tailor the presentation slides to multiple categories of audience members.
CONS: Greatly increases the amount of time required to make a presentation!