NZ Grassland Association Inc.

Guidelines for Slides and PowerPoint

Please Note: NZGA would prefer that presentations be in PowerPoint (or another electronic format) as opposed to 35mm slides. Overheads are not acceptable.

Format

Horizontal format projects better than vertical, especially in venues with lower ceilings.

Content

Simple layouts are preferable. Include no more than 6 lines per slide and no more than 6 words per line. Aim to include no more than 12 items of information, about a single idea.

Blank spaces usually convey no information. Double spacing does not improve clarity and it is better to enlarge the text or graphics to provide a larger image.

Legibility

Visual materials should be legible at a distance 6 times their diagonal dimension. A 35-mm slide should be clearly legible when held up to the light at about 25 cm from the eye. If it is not, throw it away. An A4 graph should be legible at about 2 metres. 

[This guide also defines the audiovisual facilities in a lecture hall or room: the diagonal of the largest projected (oblong) slide image (about half of a square screen) should not be less than one sixth of the distance between the screen and the furthest person in the room.]

Letter Style and Size

Use sans serif fonts (i.e., what you are reading now cf. what you read in the main heading) such as Helvetica or Arial. No letters should be less than 6% of the longest dimension of the slide, and no letter height should be more than 6 times its thickness. 

Write the text of a slide or Power Point slide in 20pt and use a bigger font for headings. Avoid text solely in capitals - upper and lower case is easier to read. If you want to emphasise, use another device.

Data Presentation

Try different chart types when presenting data. Horizontal bar charts are usually much easier to understand than formal graphs; diagrams, pie charts and graphs are better than tables where practical. Avoid text that reads vertically.

Colour

Use the international standards of blue background (most relaxing to the eye) with white or yellow text, and different bold colours for charts (but not too many). Six per cent of the audience is probably colour blind. Lines that are brown are hard to distinguish from green and red, and purple may appear blue or red, and any of these lines could also be black. 

PowerPoint

Base the slides on the Slide Master option to minimise the editing of font size, style and colour choices. 

Here is a list of Do's and Don'ts that will give you ideas to be considered in creating a Power Point presentation.

Do's

• Take advantage of the individual slide format. Keep the message of each slide clear and concise.
• Slides need to be a logical and connected order. Treat each slide like a paragraph in a story, knowing that a good story flows from paragraph to the next.
• Think along the lines of an artist drawing a landscape. Slides have focal points and layout should adhere to the same principals of scale and perspective.
• Use bulleted lists to convey groups of ideas.
• Place your graphics and text in a slide in order of importance.

Don'ts

• Remember that colour schemes that appeal to one person can be offensive to another. Let the information be the important point of every show, not your version of a jazzy colour scheme.
• Create too much animation with sweeping transitions and individual items flying in from all sides. Your audience will be overstimulated and not absorb the point you are making.
• Remember that for presentations of this type, short and sweet is the best method. Determine the point of the presentation and make sure your audience understands it when the 'show is over'!!!
• Don't use multiple backgrounds. Consistency is critical to achieve a professional look and helps to keep your audience engaged.

Font Size

How can you be certain that everyone in the audience can read the text on your slides?

While the fonts and colours you choose have a definite impact on legibility, the single biggest factor is text size. The 8H rule is the time-honoured way to make sure that even the folks in the back row can read the text on your slides.

The 8H rule says that the maximum viewing distance shouldn't be more than 8 times the height (H) of the screen; if that condition is met then as long as your text is at least 1/50th the height of the screen, then it'll be legible at the maximum viewing distance. That assumes that the person in the back row has good eyes, that the projected image is perfectly crisp, and that no other factors interfere. And it's an absolute minimum, not a recommended size.

A normal screen show slide in PowerPoint is 7.5 inches or 540 points tall, so the absolute, don't go below it minimum text size would be 540 / 50 or roughly 11 point text. For 35mm slides or good quality overheads, that's not unreasonable. For screen show projection, it's wildly optimistic. You simply can't form legible text at this height ... roughly 12 pixels ... in most fonts. For projected 800x600 screens, I'd at least double that, or use 1/25th the screen height to determine minimum text size. That translates to roughly 22 points.

Keep in mind that your screen may not always be big enough to meet the 8H rule. If not, you'll have to compensate. For example, if the screen is 5 feet high in an 80 foot deep room, it's only half the recommended size, so you'll need to double the minimum text height to compensate.

Colours

In any presentation situation, it's a fair bet that 10% or so of the male members of your audience will be colour-blind to some degree. This doesn't mean that they can't see colours at all, but they may have trouble distinguishing certain colours, most commonly red vs. green.

It's a good idea to make sure that your text and other important elements contrast with the background in both colour AND value -- that is, that you use light/dark contrast as well as colour contrast to make them easier to tell apart.

A good way to check for value contrast is to use PowerPoint's B/W View.

Simply choose View, Black & White from the main menu. PowerPoint displays your presentation as it will print to a B/W printer.