IS&T’s Guide to Effective Illustration: Images for Presentation and Publication

Based on a document written by Vivian Walworth, Mary McCann, John McCann, and Louis Rosenblum (May 1999; revised 2009)

Introduction

An important part of modern communication is the use of images—both with oral presentations and in publications—to convey the essence of the author’s message. As the methods of preparing, transmitting, and presenting images proliferate, we are all challenged to make the best use possible of each imaging technology.

The optimum image for projection before a large audience is probably not suitable for use “as is” in a publication. Conversely, an effective illustration for use in a book or journal may be utterly unintelligible when presented as a slide or poster presentation. In many cases computer generation and transmission of images provides great flexibility and makes it possible to format the same information for maximum effectiveness in each mode.

Our purpose is to provide speakers and authors a set of guidelines for producing effective illustrations. We include some simple rules of thumb and a number of examples of excellent artwork, as well as examples that illustrate some common blunders.

Modes of Display

Throughout this discussion we assume that the reader may wish to use the same material both to illustrate an oral presentation and to illustrate a publication.

Consider first the optimum image in terms of presentation. How wonderful it is (or would be) to attend a lecture or even a small conference-room presentation in which every slide is fully readable and conveys information that is easily understood during the time it is on the screen! Or to attend an interactive poster session in which each panel can be read and understood at a distance of 5 feet.

How do the requirements for presentation images differ from those of images for use in handouts, images for proceedings, journal or book publication, and images to be reproduced in CD-ROM format?

Time for Viewing

The amount of information to be included in a visual—i.e., an image to be projected in conjunction with an oral presentation—should match the length of time the speaker intends to spend discussing that information.

The published image has the benefit of a printed caption that may help to explain the details, and the reader may choose how long to view the image. Consequently, it is practical to include more information in the printed image than in an image presented on the screen.

Use of Color

The image for presentation may be enhanced by the liberal use of color, and the speaker can guide the audience through the material that is shown, with easy reference, for example, to a red curve, a blue one, and a green one. The corresponding published image may appear in black and white, with the curves encoded by line pattern, rather than color, and the reader is left to follow the printed discussion on his own.

Illustrations for Multiple Display Modes

To save time, it is advisable to anticipate all possible uses of an illustration as a first step in its design. For example, an illustration comprising a set of curves may be suitable for all of the above modes if the curves are encoded in both color and line pattern and drawn in a horizontal format. A title may be included for presentation use and cropped off, to be replaced by a caption for publication use. With a sufficient margin outside the axes and their labels the same figure will be suitable for both projection and CRT display.

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Image Composition

The challenge is to design and produce illustrations that can serve in one or more imaging modes without compromising quality. It is important to decide in advance just how you may want to use each image and to make informed decisions regarding its content and its physical features.

Digital Images

Computer-generated illustration offer several advantages. Once in digital form, the images may be edited and formatted to fit a particular presentation or publication requirement. Such images may also be transmitted via e-mail and other forms of electronic communication/posting, expediting rapid publication and/or the sharing of information with colleagues in remote locations. When images for publication are to be transmitted in digital form, it is advisable to obtain specifications from the publisher to be sure that your material can be properly utilized. Many book publishers provide style guides, and most journals list their specifications in the front of each issue. A good rule of thumb is to make sure that your original image is scanned or created at a minimum of 300 dpi of the anticipated publication size. Images submitted to publications should be in EPS or TIFF format.

Slide Layout

A projected image is best presented in horizontal format, to assure that it will be visible to the entire audience. The exact ratio of width to length will depend on the type(s) of display (4:3 for CRT, 3:2 for slides). Vertical format almost ensures that the lower part of the image will not be visible to most of the audience.

The image should be designed to fill most of the available area. It is frustrating to viewers to strain to see fine details of a figure that is surrounded by wasted blank space. Avoid placing critical information close to the edges.

Dimensions

Throughout this manual we refer to dimensions of text and labels in terms of point size. Points are traditional type measures, denoting nominally the vertical distance between the tops of the highest ascending letters (like h) and the bottoms of the descending letters (like p). A point is approximately 1/72 in. (0.35 mm).

Line-to-line spacing is also expressed in points. The designation of type size and spacing is stated as type size/line-to-line distance for example, 10/12 (also described as “10 on 12”) refers to 10-point type with 12-point line-to-line spacing, also known as leading. Larger dimensions, such as margins and column width and length, are often stated in picas. A pica is 12 points, or 1/6 inch (~4.2 mm). See Figure 1 for a comparison of scales in terms of inches, millimeters, points, and picas.

Specifications

For journal and proceedings publications, images should be designed to fit within a single column of the two-column format that prevails. The width of a single column is usually about 20 picas (3.33 in., 85 mm). Within the column the layout may be horizontal, vertical, or square. Some published images and tables are best presented in 1.5- or 2-column format.

Note: A convenient rule-of-thumb for relating presentation images to publication specifications is that a single-column image (20 picas) is approximately 1/3 the width of a horizontally composed 8.5 x 11-in. master for slides or overhead transparencies.

Titles and Captions

Here the requirements for presentation and publication differ considerably. It is frequently desirable to include in an image for projection a title that will assist the audience in understanding the material. For publication, the title is incorporated in the caption, and the caption should contain enough information so that the reader can understand the figure without searching through the text for an explanation. The caption (or footnotes, in the case of tables) may correspond roughly to the remarks of the speaker when the same figure or table is projected during an oral presentation.

Integrity

An essential characteristic of a high-quality illustration is that the information is presented accurately and without distortion. For example, two curves presented together or the series of blocks in a bar chart should be plotted on the same scale, to avoid a visual impression that may not be in accord with the facts. Publishing or presenting a misleading illustration is much worse than going without one.

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Optimizing Text-Only illustrations

Figures 1 through 5 below are examples of text slides. Of these five figures, only Figure 2 would be entirely suitable for projection as detailed below.

Readability

Ease of comprehension

The symbols and fonts used in an illustration all contribute to the ease with which the viewer or reader comprehends its message. One of the most certain ways of losing the attention of an audience is to project images that include type too small to read easily.

1. Use large type. First line in 30-point Times Bold is fine, but 18-point type would NOT be large enough!
2. Use enough space between lines. The line-to-line space is 40 points, with an additional 4 pts between items.
3. At 30-pt size there may be 10 words per line.
4. Caps & lower case are much better than ALL CAPS!
5. Every word in every visual should be readable from the back of the room.
6. This is the 9th line of an effective visual.

For an illustration to be used in an oral presentation, all characters must be scaled so that the entire audience can read them. That requirement imposes a strict limit on the amount of information to be included on a single slide. As an example, Figure 1 shows a 9-line message of maximum length for projection under typical circumstances. The full-page version is shown in Appendix A in 30-point Times Bold.

Note: Appendix A contains full-page versions of Figures 2 through 6. We encourage you to use those images for judging readability versus viewing distance.

Fonts

For both oral presentation and publication it is most effective to use such easily read fonts as Palatino Bold, Times Bold, Helvetica Bold, and Univers Bold. See Figure 2 for examples of these fonts. Note also the horizontal format, the use of upper- and lower-case letters, the ample line-to-line spacing, and the dot that identifies the lower left corner. Figure 3 compares Palatino Bold with some fonts that should be avoided.

Size of Type

For slides and overhead transparencies, the most important consideration, as discussed above, is readability. A good test is to view the illustration at letter-paper size at a distance of 8 feet (2.4 meters). If you cannot read every word and label comfortably at this distance, switch to larger type.

If a figure for publication is submitted as hardcopy, we recommend that the original figure be at least 1.5 times the desired final size, with characters sized to appear as 8-point or 9-point type on the printed page. Figures to be embedded digitally within text files are best prepared at final size.

Point size is relative within a given font and differs significantly among fonts. See Figure 5 for examples of relative point sizes for several families of fonts. Figure 6 shows a range of point sizes for Times Bold and Helvetica Bold.

Figures 5 and 6 are truncated here to fit horizontally within the text page format. Full versions are included in Appendix A.

Figure 3 contains 9 lines of 30-point type, which will be fully readable at 45 feet (11.5 meters) when projected onto a 10-foot (3-meter) screen or at 22.5 feet (5.8 meters) on a 5-foot (1.5-meter screen). Those readability figures pertain to viewers who have 20:20 vision. Note that many members of the audience may have vision poorer than 20:20. In general, an effective text visual will have at the very most 90 words, with up to 10 words per line. For a title, 36 points is not too large.

Rule of thumb: For type or printing not identified by point size, a good rule is to have all characters at least 1/4-in. in height.

Use of Templates

Visual effectiveness can often be enhanced by numbering statements; adding arrows or bullets before key statements; using two or three type sizes (usually in descending order); indenting successive lines; or adding decorative borders, color, and/or shading. These options are readily available in template form in such programs as Microsoft's PowerPoint, Adobe's Persuasion, and Corel's Presentation. See figures 7 and 8.

A note of caution: Typical template programs incorporate up to five levels of type sizes for body text (See Figure 7). Avoid using the default values for the lower levels, as they are generally too small for presentation use. Use larger type sizes and limit the levels. For example, two slides with 3 levels each will be more effective than one slide with five levels.

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Optimizing Line Art

Graphs and Curves

It is important for both projection and publication that graphs show clearly the important lines, points, numbers and legends. Grids and fine scale marks should be omitted, so that the message is easy to discern. Avoid using the original printout from an instrument if the lines are light or the background includes a grid pattern. Be sure to include adequate quantitative information on the axes.

Figures 9(a) and 10(a) are examples of excellent illustrations prepared for publication and also easily adapted for presentation. Note that each curve is clearly identified. The lines are well differentiated, and the labels are easily read. Only necessary intervals are indicated along the axes, and there are no distracting grid lines. The accompanying versions, Figures 9(b) and 10(b), were specially designed to illustrate some common blunders.

Line Width

The essential lines in the figure should be bold rather than light. If your program allows specification of line width in points, set width so that final printed line is at least 1 point. Lines not important enough to be thick and bold should be omitted.

Labels

It is helpful to include labels that identify specific curves or objects within a single illustration. If there is space within the figure for word labels, they are often preferable to codes or symbols that require the reader to look back and forth between caption and figure. Often illustrations in a series are more effective if they contain short labels that differentiate the members of the series.

Abbreviations

Abbreviations or acronyms that are readily understood are usually effective because the characters can be larger and bolder than those in words fully spelled out.

Significant Figures

It is usually advisable to limit the number of significant figures in labels on a graph, unless the author is making the point that very high precision in the data is an important aspect of the illustration. Error bars often provide a good indication of precision without cluttering the image.

Schematics, Flow Diagrams, Charts, and Equations

During a presentation an author has the opportunity to guide the audience through a fairly complex image. For publication, a diagram or chart can be even more complex, as long as the caption or labels help the reader to comprehend the material. Figure 11 is an example of a diagram that works well in either mode. Figure 12 is suitable for publication, but would be difficult to present by projection because of its vertical format.

Figure 13 is good for publication in 1.5 or 2 columns, but contains fine detail that would not be fully readable if the image were projected.

In chemical structures rings and type size should be consistent in scale. For projection o, the 6-membered ring width should be at least 15 mm (see Figure 14). Suitable published width for a 6-membered ring is 6 to 9 mm with incorporated type size 8 to 10 points. There are several good software programs for drawing organic chemical structures.

Major word processing programs include equation editors that make it easy to present mathematical equations in highly readable form. As with text slides, a safe limit is 9 lines, with type size 30 points. Do not include more math in a visual than you will have time to discuss.

Tables

Tables to be projected are best presented in horizontal format and should not contain more than 9 rows. The table for projection may have a short title or none at all. Each column of the table should have a brief heading, with units of measure included. Word entries are best aligned on the left or centered, and numerical entries are usually most readable if aligned on the decimal.

There is much more flexibility in format for tables to be published. The table may be horizontal or vertical and single- or double-column width. The title of a published table should be self-explanatory without referring to the text. Footnotes may be included to explain details.

Figure 15 is a table that works well for publication, but would be difficult to use in a presentation. Figure 16 is a table that is suitable for both modes.

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Continuous-Tone Images

Photographs

Both color and black-and-white photographs are useful as slides for projection during a presentation. On the other hand, the cost of color reproduction often limits the number of color illustrations for publication. In some cases satisfactory black-and-white published versions are prepared from color images.

In making a photograph to demonstrate equipment it is important to provide good lighting and an uncluttered background. For sets of slides designed to compare before-and-after images—for example, in color correction processes—use side-by-side images rather than successive presentation. It is important here to preview the pair side-by-side to be sure that the comparison is effective.

When scanning images for inclusion in a publication, be sure to scan at a minimum of 300 dpi at the expected printed size. Print out images to be sure of satisfactory reproduction. Request color proofs for your approval when you submit a manuscript that includes color illustrations.

Micrographs and Macrographs

In addition to the general requirements for presentation and publication of photographs, consider the importance of showing scale in micrographs and macrographs. The simplest method is to add a scale bar to the image, showing an appropriate reference dimension. A clear background around the scale bar may be necessary (see Figure 17). Note that although scale information is generally included in labels of scanning electron micrographs, it may need reinforcement to be read easily when the image is projected. Some scanning electron microscopes can superimpose readable scale bars within the image area. An alternative technique for photomacrography is to include a familiar object, such as a ruler, a common pin, or a coin, to indicate the magnification. The least satisfactory method is to include the magnification in the caption. The author has little control over the final dimensions of a printed illustration, and the information in the caption may thus become erroneous.

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Projection of Images

In projection, the most important concern is that the projected image, or visual, will be easy to read at the maximum viewing distance likely to be encountered. Characters must be large enough and clear enough so that each person in the audience can read every word easily. It may be helpful to include a title that will assist the viewer in understanding the significance of the image. If the image is to be projected in a large hall it is best to use a horizontal format, with the entire image high enough on the screen so that heads of viewers in the front rows will not block the view for those seated in rows further back.

Being part of an audience is a good way to learn what works well. Learn from the mistakes of others, not from your own! Try sitting in the back row or at the far left or right when you attend a presentation.

Information Content

In an ideal presentation, the timing of the image projection is tied in with the timing of the oral presentation. It is troublesome if the speaker moves on to the next slide before the viewer has had time to appreciate the full significance of the first image. Conversely, it is distracting to have an interesting image remain on the screen while the speaker is trying to turn the attention of the audience to another topic. The content of each visual must be limited to material that the audience can readily grasp while you discuss the information presented.

In situations that demand displaying an entire table or set of equations for context, with the understanding that the audience will not be able to read the details, consider providing the same material, either before the presentation or afterward, in the form of a handout. Another useful technique is to follow the “context” slide with another slide that presents a readable “close-up” of a selected area.

Color versus Black-and-White

Color may be used to enhance visuals and to aid in the discussion of the material. If the same line art is to be used in both a presentation and publication, it is advisable to include coding by line pattern, which can be identified in the black and white version.

Use color combinations that provide contrast in brightness—for example, white or yellow characters on a blue background. Avoid low luminance contrast combinations such as red on green, red on blue, magenta on blue, green on blue, green on brown, yellow on white, blue on white, red on white, or magenta on purple. Remember that for persons who have deficiencies in color vision, it may be particularly difficult to distinguish red from green. In color transparencies, avoid showing a white surround. Use an opaque mount to enhance the effectiveness of the color image.

Even though a color scheme may appear attractive on a monitor, note that printers usually produce a less satisfactory color rendition. Be sure to check the readability of all slides by projection in a simulated lecture room environment.

Black-and-white visuals are often less effective than color visuals. Black lines on a white background make white-light laser pointers virtually invisible. The projection of white-on-black slides leaves the room totally dark and demands the use of a pointer.

Projection Conditions

Among the factors that are usually beyond the control of a speaker making a presentation are: screen size; screen brightness, directionality, and freedom from blemishes; room size and shape; ceiling height; presence of low-hanging chandeliers; maximum viewing distance; illumination level when room is “dark”; availability or type of a laser pointer; podium position and lighting; type and location microphone; quality of the sound system; quality and condition of projector; projector location; and noise from adjacent rooms or corridors. All of these can effect your presentation and thus should be considered when creating a slide.

Room and Screen Dimensions.

In designing visuals be prepared for the worst possible situation. A room at a conference in a hotel setting may be as large as 45 x 95 feet (14 x 30 meters). For readability that situation will require a 20-foot screen. With a 10-foot screen only those seated in the front half of the room and endowed with 20:20 vision would be able to see the image well. In most situations the use of characters of at least 30-point size is essential for an effective overhead transparency.

For classroom or conference room presentation, assume that the back-row viewer may be at 20 to 40 feet (6 to 12 meters) and that the screen may be as small as 5 x 5 feet (1.5 x 1.5 meters). Again, use at least 30-point characters.

Testing Readability of Visuals

The finest print on a slide should be easily read at a distance of 8 feet when viewed directly from a letter- or A4-size paper. Never assume that a slide that looks fine when projected in an office or conference room will be satisfactory for lecture hall or classroom use. Try projection in a long corridor if a large room is not available.

Making the Presentation

Be careful not to stand in the way of a projected image. Be sure to test your slides using a projector provided by the conference organizer. If you need to refer to a slide a second time during a presentation, make a duplicate slide. If you need to compare slides, create a slide with them side-by-side.

Note that the position of a podium lamp or its brightness may scatter light from the screen and interfere with effective viewing of projected images. It is often preferable to turn off that light and to use instead your own small penlight if it is necessary to consult your notes during projection.

Use of Pointers

Be aware that a He-Ne laser pointer may not be seen by those with color vision deficiencies. Note, too, that white-light pointers do not show up well on a white background. To steady the pointer direction, try resting the aiming hand against your other hand or the edge of the podium and pivoting the pointer, rather than waving it “freehand” toward the screen.

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Images for Direct Viewing

Poster Presentations

The measure of a successful interactive poster presentation is its effectiveness in presenting only the main points of the paper on a single panel. The title should be readable at 6 to 8 feet. The observer should be able to grasp the most significant information readily by viewing the entire panel at a distance of at least 5 feet. The author is then free to stand aside and engage in discussion with the more interested viewers. With a poor poster presentation a few viewers standing close to the panel trying to read the material obscure it completely for others. If the author tries to “walk” each viewer through the panel display, it is also obscured. Use a laser pointer instead.

Handouts

An author making a presentation may choose to provide copies of the principal figures as handouts. The availability of copies of a projected images helps to preclude the intrusive sound of shutters snapping and the occasional inadvertent flash during a presentation.

Publication

In preparing illustrations to accompany a manuscript for publication, authors should first be sure to comply with format instructions provided by the journal or book editor. Beyond such requirements, the illustration and its caption should aim for ready comprehension.

Many readers often skim through an article quickly by looking only at the figures before deciding to read the text. For such a reader, an effective set of illustrations is somewhat akin to a good poster presentation. Here a horizontal format, as recommended for projection display, is usually compatible with printing in a single column of a 2-column page. However, there is a good bit more flexibility on the printed page, and vertical or 2-column figures and tables may also be appropriate.

Presentation in Electronic Form

The horizontal CRT display ratio of 4:3 is unlike horizontal ratio of a printed page, which in most journals and books has a vertical format, such as 8:11. Depending on the software used, either the author or the reader may be able to choose the display format for viewing and/or for downloading. In Acrobat, for example, the author controls the format, whereas in web browers the reader can do so.

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Checklist

Slide Masters

__ Horizontal Layout
__ Easy-to-read, bold font
__ 36-point type for title; 30-point and 24-point for text
__ Maximum of 9 lines of type or equations
__ Maximum of 10 words per line
__ Colors selected for high contrast
__ Curves bold, encoded by line pattern or simple labels
__ No grid lines underlying curves
__ Clear labels on graph axes
__ Text & labels on letter-size sheet readable at 8 feet

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Recommended Reading

Anon., AIP Style Manual, 4th. ed., American Institute of Physics, 1990.

M. H. Briscoe, Preparing Scientific Illustrations: A Guide to Better Posters, Presentations, and Publications, Springer Verlag, 1996.

J. S. Dodd, Ed., The ACS Style Guide: A Manual for Authors and Editors, American Chemical Society, 1997.

R. Gaughan, Technical Presentations: Basic Rules for Success, OE Reports, No. 139, July 1995; Technical Presentations: Entertain and Impress, OE Reports, No. 140, August1995 (SPIE). Technical Presentations: Making Visual Aids Work, OE Reports No. 143, November, 1995; Technical Presentations: Bringing It Together, OE Reports No. 145, January, 1996. Available via http://www.spie.org

M.Y. Rabb, The Presentation Design Book: Tips, Techniques and Advice for Creating Effective, Attractive Slides, Overheads, Multimedia Presentations, Screen Shows, 2nd edition, Ventana Communications Group, Inc., 1993.

E. Tufte, Envisioning Information, Graphics Press, 1990; E. Tufte, The Visual Display of Quantitative Information, Graphics Press, 1992; E. Tufte, Visual Explanations, Graphics Press, 1997.

See also graphics instruction manuals that pertain to specific software.

Appendix A

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