(Not) Posting My Slides

Greg Ingersoll

Mon 09 September 2013 - 11:34:31 CDT

#presentations #optics

Last week I presented a paper at SPIE Optics+Photonics in San Diego. It was a good conference, and I think the people who attended my session were happy with it. (Also thanks to the CalTech and U of Arizona people for a good lunch discussion after the session.)

Here I’m not going to get into the (ongoing) research, but I want to highlight a couple things I did with the slides that you might try in your own presentations.

First, sorry (long-time friend of mine) Geoff, but I’m not going to post all of the slides. Remember, slides don’t stand alone as a document. In fact, the point of this presentation at the conference was to highlight salient sections of the paper I had already written. So, if anything, I would post the paper.

Now, slide number 1: a plot of diffraction efficiency data generated in Scilab.

A slide with a plot

A few things to note here:

  • No bullets. (And yes, I understand the irony of including this point in a bulleted list.)
  • The plot is big on the page. No clutter around it. It uses all of the available space while leaving some margin so things don’t look too crowded.
  • There is a title on the page, but it’s short (and big). By itself, this probably doesn’t make sense, but in the context of the talk, the title serves as a reminder of where we are.
  • Lines have colors and textures. The colors have good contrast vs. white, and show up well on a projector. (Hint: don’t use cyan or yellow.) Also the colors are different enough from each other. Finally, the dashed lines help distinguish the curves if you have issues seeing color or if the plot is printed in black and white (as it is in paper published in the conference proceedings).
  • There is a clear, consistent font. The basic Keynote template I started with uses Gill Sans Light. The smallest non-subscript text is roughly 28pt. And, importantly, the plot axes and legend use the same font as the rest of the presentation.

That last point is not difficult to achieve, but it is time-consuming. Scilab generates good plots, but doesn’t have a lot of flexibility in formatting. Also, I’ve found that if you play around with dashed lines in Scilab, they look fine in the application but don’t export well. Fortunately, Scilab will export SVG vector graphic files that can be tailored in Adobe Illustrator (or Inkscape or similar) to change fonts, add annotations, change colors, and change dashes. (Caution: The initial vector structure you get will be a mess. But with a little effort, you can split/combine paths and group/ungroup entities to get to something that makes sense.)

Another trick is to keep consistent axis scaling in Scilab as much as makes sense:

--> plot(...);
--> a = gca(); // get current axis
--> a.data_bounds = [xmin, ymin; xmax, ymax];
--> a.tight_limits = "on"; 

This way, you can reuse axis formatting–line weight, color, font–across multiple plots in your presentation. (It also helps the audience understand relative scales between data sets.) And finally, keeping everything in a vector format as long as possible maintains image fidelity when you resize in the presentation slide.

Now slide number 2 (and 3): a full-bleed photograph of part of the lab setup.

Full bleed photo with context

Large photos are great, obviously, for illustrating things that are difficult to describe (like an experimental lab setup). The first photo has the room lights on, and when this slide is up, I can describe the position of the holographic plate on the rotation stage, the location of the laser source, etc. But it is difficult to see the two diffraction spots on the screen. However, when I include another photo taken from the same position with the room lights off, you can easily see the diffraction spots.

...and the same scene with contrast

You can’t see the apparatus well anymore in the second picture, but that doesn’t matter because context was established in the previous slide. When the slideware–Keynote in this case–dissolves between the photos, connection between the two is obvious, and that can be worked into the description during the fade: “The output spots are easier to see once we turn the room lights off.”

(Also, don’t forget to practice with technology interruptions. My presenter display–showing the next slide and a timer–decided not to work during the presentation. My laptop display was just mirroring the projector, and there wasn’t time to fix it. Things still went reasonably well.)

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