When giving a presentation with a diagram, pretend the diagram doesn’t exist

::Wendy:: suggested enabling a means of displaying pictures on the blog without messing up the display of the whole post.

Actually, I've simply given up on the pretty diagrams since everybody seems to hate them. You may have noticed that I've been using ASCII art instead. It's certainly easier for me to write, though it's also a bit uglier.

One thing readers may not have noticed is that I try to make the article readable even without any diagrams or pictures at all. Sure, you can look at the diagrams if you want, but the article should still make sense if you don't. (And if the image is essential, I'll at least give it some ALT text.) I do this out of consideration for my readers with visual impairments.

When you're giving a talk, you have to make sure people can follow what you're saying even if they can't see your slides. They may be visually impaired. They may be stuck behind a pillar. They may be sitting so far back that they can't see your slides clearly. If your talk is being recorded, the person listening to your talk might have downloaded only the audio portion. Or your diagram may simply be unreadable.

Don't just say, "You can see the trend from this graph." Describe the trend. "The system remains responsive until traffic reaches X requests per second, at which point the throughput nosedives very sharply."

Don't just say, "This is the block diagram for our system." Describe the block diagram. "The XYZ component is the kernel-mode component upon which the user-mode components ABC and DEF are built."

If you want to point out elements in your diagram in your talk, don't just point and say, "It goes from here to here." Describe where "here" is: "It goes from here, ABC at the top of the triangle, to here, DEF at the bottom left corner." That way, people who are too far away to see where you're pointing (but who have a hard copy of the slides in front of them) can still follow along.

Basically, when you have a diagram, pretend you don't. Write your text (or give your talk) as if there were no diagram at all.

Comments (15)
  1. Tom says:

    I appreciate the fact that you work hard to make sure your blog entries are readable.  I use an alternate browser and sometimes the drawings you make are not legible.

    But, like all advice, the advice to pretend you have no pictures is not an absolute.  Presentations should be targeted to an audience, so if you know your audience is not visually impaired it may be okay to refer to the drawing without describing it.  If your audience is by general admission or unknown, then following Raymond’s advice makes perfect sense.

    I know this seems obvious, but I thought I might head off some of the nitpickers early.

  2. Adam V says:

    @DWalker59: Reminds me of a number of my college classes. Not only would they read from the slides, they printed out all the slides for the next two weeks and had them at the door. So you only had to show up once every couple of weeks, pick up a copy and then leave. (You could even show up right as class was leaving, then dart in and grab a copy, if you were particularly engrossed in a game of Starcraft^W^W^W^W^W^Wbusy that day.)

  3. DWalker says:

    The worst thing is when someone gets up and gives a talk with slides and simply *reads the slides*.  If the presenter isn’t going to add anything at all to the content of the slides, he or she doesn’t even need to  be there.

  4. Johan says:

    There are other good reasons to avoid "It goes from here to here" than visual impairments/obstacles. It adds unnecessary cognitive load to map each here to what you’re seeing and both reading and hearing the involved nouns at the same time should make it easier to recall afterwards. After all you have two things to remember: what you heard and what you saw.

  5. Another good reason for providing good text in a blog post (though not so much for presentations): search engines can index it much more effectively.

  6. Falcon says:

    Adam Rosenfield’s comment reminds me of looking up songs with unknown artist and title – if you know some of the lyrics, you can type them into a search engine and go from there. However, if you only know the song’s melody, it’s considerably more difficult!

  7. Brian Tkatch says:

    I like to think, that if it cannot be explained without the visual aid, the presenter does not understand it that well himself. I think books have this same issue.

    If the speech or text explains it well, a graph is helpful as an aid.

  8. JM says:

    @Falcon: though there are search engines for that too. http://www.musipedia.org is a good one for classical and folk tunes (it’s not as up to speed about pop songs).

    For those interested in searching by image (rather than searching *for* images), try http://www.tineye.com.

  9. Jonathan says:

    Brian Tkatch: I have to disagree. In many cases, you’ll have to describe the diagram in (many) words, while the listener tries to builds a mental image of the diagram in his head. I’ve actually resorted to drawing on paper when listening to some explanations.

  10. Brian Tkatch says:


    I see. When the details are important, the diagram helps.

    What i meant to say (but didn’t) was that relevant to concepts and explanations, the requirement for a diagram is a lack in the presenter. Once the concept is understood, diagramming a good sample can help make it sink it. However, if the explanation is completely based on a diagram it is not explained well.

    There is one exception. If the diagram is what the explanation is about, it needs to refer to the diagram. For example, in TCP/IP Illustrated, the author present a diagram of his network, and of an IP packet. He refers to those diagrams a lot because that is what he is explaining. Though, even then, he does a great deal of explanation and one could learn most of it without the diagrams.

  11. Ben says:

    @ Jonathan and Brian. Part of the issue here is whether you are a visual thinker or not. I like to think in words and have diagrams explained. Many of my co-workers are completely unable to understand or explain without the use of whiteboard. http://www.dilbert.com/strips/comic/2009-03-11/  The secret is to ask the person how they prefer to have you explain things. For me, I give a visual person a pen and get them to draw as I talk.

  12. Ben says:

    In relation to the topic at hand, when presenting you need both. A good explanation for the auditory people, and a good diagram for the visual.

  13. Brian Tkatch says:


    That’s a good point. Indeed, i am auditory. At least in that i usually say "i hear" as opposed to "i see".

    However, a good image helps me as well. Wouldn’t the visuals also benefit from hearing?

    And what about in a book? Where the words are read? Whilst some read the words in their head, others don’t? Wouldn’t that then also be visual?

  14. ::Wendy:: says:

    I like to think that the language of delivery (picture/words/audio/braile etc) should be tailored to the intended audience and the technology developed to effectively support it (e.g. Operating systems).  Now if Raymonds audience were fine artists (or interaction designers) lack of pictorial illustrations would undermine the efficiency with which he conveyed his message.

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