Your slides

Many people use densely written transparencies, where several theorems or whole proofs are packed. This is a bad thing to do; it will tire your audience very soon, since it forces them to perform three tasks simultaneously: reading your text, listening to you, and thinking to themselves how badly prepared your talk is; not to mention the strain on their eyes. If you present a proof then the listener does not have to read it as he hears it; a couple of lines with e.g. a rough sketch of the proof or some formulas will be enough, and very helpful. If you have five five-line theorems on one transparency, then consider cutting it into five pieces and presenting them one at a time. Covering parts of your transparency with a piece of paper is better than leaving the whole thirty-line transparency visible all the time, but still it is not as good as cutting into pieces: if you do cover the transparency you will inevitably move it around and create all kinds of shadows, tiring your audience and distracting their attention.

Another thing you should bear in mind is that people will always lose concentration from time to time, and some of them will forget a definition or statement they saw just a minute ago. In order to help them, it is a good method to leave crucial definitions visible for a long time, e.g. by putting them on several slides if you are using a video projector. If you are presenting a long proof you should, for the same reason, leave the assertion you are proving visible until the end of the proof.

Some people open a long document - typically a paper - on their computer and make their presentation from this, scrolling down the text during their talk. I'm sure they realise that this is not a good thing to do, but apparently they think it is not too bad either. They are wrong.

See also: Give opportunities to catch up again

A. Georgakopoulos: How to give a talk that is not too bad.

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