The thing speakers do with their hands
Watch someone explain a diagram without a screen. They point. They trace a line. They circle the part that matters and say "this bit."
Now watch the same person explain the same diagram on a projector. They point at the screen behind them, which nobody watching remotely can see, and say "this bit here" while forty people try to work out which bit.
The gesture is doing real work... it is joining the word to the thing. And it is the first casualty of putting the diagram on a screen.
What annotation restores
The ability to mark the screen itself, live, from where the speaker is standing.
A touch surface at the lectern shows what the room sees. The speaker draws on it. The mark appears on the projector, in the stream, and in the recording, at the moment they made it.
That sounds small. In use it changes three things:
"This bit" becomes a circle. The most common sentence in any explanation stops being ambiguous.
The remote audience gets the gesture. Somebody watching at home has always been the person who cannot see what is being pointed at. Now they can.
The recording keeps it. Watched back in a month, the marks are still there, still attached to the moment. A recording of someone gesturing at an unmarked screen loses the explanation entirely.
Where it earns its place
Not everywhere. Being honest about that matters, because a feature used badly is worse than one used never.
Genuinely useful:
- Explaining a diagram, chart, map or floor plan
- Working through a passage of text... underlining a phrase, bracketing a section
- Comparing two things on screen... circling the difference
- Any moment where "this one, not that one" is the point
Usually not:
- Decorating slides that were already clear
- Underlining every third word for emphasis
- Anything the speaker planned in advance... that belongs in the slide
The distinction: annotation earns its place when it responds to the moment. If it could have been designed beforehand, design it beforehand.
Practical notes for a speaker
Draw slowly. Faster than handwriting speed reads as scribble, especially to someone watching on a phone.
Use one colour and mean it. Multiple colours look busy and mean nothing unless you have established what they mean.
Circle, do not shade. A circle is legible at any size on any screen. A shaded region turns into a smudge on a small display.
Clear it when the point ends. Marks left on screen after the moment has passed become visual noise. If the next point is different, start clean.
Practise once. The first time anyone annotates live, they draw too fast and too much. Ten minutes beforehand is enough to fix that permanently.
Practical notes for whoever runs the desk
Decide who clears the screen. If the speaker forgets, someone should. Agree beforehand who that is.
Check it appears on every output. Room, stream, recording, any second screens. Marks that appear in the room but not in the stream are worse than no marks... the remote audience hears "this bit" and sees nothing again.
Do not switch away mid-mark. Cutting to a camera while someone is drawing loses the point they were making. If they are annotating, stay on the screen.
Why this exists at all
The honest answer: because the screen took something away, and I wanted to put a piece of it back.
Presentation technology has spent decades making it easier to show prepared material and harder to do anything unplanned. A speaker with slides is more polished and less responsive than a speaker with a whiteboard. Something real was traded.
Annotation is a small piece of the whiteboard returned... the ability to respond to the room, to mark the thing you did not know you would need to mark, to answer a question by pointing at the answer.
It is not the most impressive thing I have built. It is one of the few that makes a talk better rather than making a talk look better, and those are worth more than they demonstrate.