The art and science of presentation: 35-mm slides.DR Sahu, AN Supe
Department of Surgery, Seth G. S. Medical College and K. E. M. Hospital, Parel, Mumbai - 400 012, India. , India
Correspondence Address: Source of Support: None, Conflict of Interest: None PMID: 11435658
Source of Support: None, Conflict of Interest: None
Keywords: Audiovisual Aids, Health Education, Human,
During a presentation, both the visual and auditory senses are available to absorb information and here assistance in the form of a visual aid is useful. Thirty-five mm slides are amongst the most commonly used visual aids. Preparing slides needs both a scientific and an artistic approach. The emphasis of this article is on how to prepare better slides and not how to stand up and deliver a talk.
? They are universally used and facilities for this kind of presentation are likely to be available at most places.
? They can be used for a small as well as a large audience, in small group discussions, lectures and conferences.
? Slides help to focus the attention of the audience, save the efforts and time spent on explanation, and improve the effectiveness of the message.
? They can be combined with multimedia presentations.
? Slides are good visual aids for presentations with numbers, figures or new concepts.
? They can also serve as the speaker’s notes for important points, and they can be useful in pacing the talk.
? They can be used repeatedly.
? They are easy to prepare using a computer and camera.
According to the organisers’ instructions: It is essential to find out the facilities available and time allotted for presentation. Ascertain what equipment is available. One should know if the facility for slide/ multimedia projector is available! Before one prepares your presentation for a dual projection, make sure the facilities for the same are available.
According to the audience: Each presentation should be an individualised one. Change the concepts and slides to best suit the needs and knowledge of the target audience. To do so one needs to know the audience.
To motivate: Most people listening to a 10-minute talk will ‘take home’ no more than five key points from the talk. Highlight these five key points (take home messages) that can motivate the audience to think, remember or practice your concepts.
According to the time: About 80% of the effort comes before the presentation– the actual talk comprises only 20%. But the success of the latter depends on the meticulous preparation. Get an early start on the preparation; it is another matter that most of us end up working until the last minute. A presentation should never begin with an apologetic note ‘I am sorry but I did not get enough time’. If the speaker has devoted 10 hours for the preparation, each individual in the audience has probably given at least an hour to attend the presentation, and if there are 100 individuals in the audience, 100 man-hours are being utilised. Lack of time should not be an excuse.
? Use slides to visually reinforce the talk and not substitute it; the audience might as well read the slides instead of listening to you.
? “Tell ‘em what you’re going to tell ‘em. Tell ‘em. Tell ‘em what you told ‘em”: give an outline at the beginning and wind up with a short summary.
? Start with a bang: In a ten-minute talk, there is less than a minute to convince the audience that there is something interesting in the presentation, hence have a good introductory or outline slide.
? Follow a logical sequence: Start with broader, more general topics and progressively go deeper.
? One concept per slide: Use one slide to present one (and only one) concept.
? Each slide should take about 45-60 seconds for discussion, so use not more than 15 slides for a ten-minute talk.
? For number of words per slide and total number of slides count more than the actual (Less is more), where as for the size of the text and graphics consider the biggest possible as small (Big is small).
A good slide is “appropriate, accurate, legible, comprehensible, well-executed, interesting and memorable.”
Appropriate: Have a good reason for showing each slide and make sure the prepared slide fulfils that reason.
Accuracy: Verify the accuracy of spellings (including the names of people and organisations). Verify the accuracy of the data. Inaccurate spellings will interfere with the flow of thoughts and understanding.
Legibility: Do not make your slide into a ‘Snellen’s chart’ for the audience. Illegible slides will force the audience either to shut off their minds or to spot out what is written on the slide instead of listening to the presenter. A slide that is legible without magnification when held at a distance of eight times its height i.e. when held at arm-length, will be legible when projected.
Simplicity: Simplify the concepts, text, and graphics. Keep the presentation focused on the message; do not get carried away with designs and graphics. At the end of the presentation the audience should be marching out discussing the ideas, not talking about the slides.
Clarity: Remember the “Burma Shave Rule”– do not pack any more into a visual than you could read off a hoarding driving by at highway speed.
Consistency: Be consistent in use of font, colour, background, and with noun and verb phrases, tense, etc.
The first slide should show the title, the presenter’s name and the presenter’s institution. This should be followed by an introductory slide or the outline slide and then the main contents. The last slide should be the summary or the conclusion slide. Each slide should be self-explanatory and have a title for each slide similar to a newspaper headlines – let the slide speak for itself.
Most of the screens are horizontal; hence, it is better to stick to the horizontal format with a ratio of 2:3. Do not mix horizontal and vertical formats in one presentation.
Colour increases the visual impact, and also improves visibility. Different colours have different luminance: white has a luminance of 100%, yellow - 89%, green - 59%, red - 30%, blue - 11% and black - 0%. For a better visibility, colours with maximum difference in luminance should be used if they overlap each other and avoid blue on black, red on blue or green on red.
Dalal et al in their study with 36 different backgrounds showed that the most attractive slides were not necessarily the most clear and easy to recall. Instead, simpler slides were the most easily recallable. Hence, a simple slide should be used, if one has to impart knowledge. They recommended slides with a uniform dark coloured background (blue, green or purple), with a separate background (red, green or purple) for the title on each slide and white letters for the text and yellow for the title.
Be aware of the fact that some colours seen on the computer monitor will get changed in the final product. This is vital if an exact colour is important. Only the best monitors and film recorders will give good colour reproduction (WYSIWYG - what you see is what you get).
For the benefit of colour-blind people, choose highly saturated colours and thicker lines and avoid combinations of red/green, brown/green, blue/black and blue/purple.
Font size: Use a minimum of 18-point font for the slide text (24 is better), and minimum font size of 36 points for the titles on each slide.
Font character: Use a sans serif font such as Arial, Helvetica, Tahoma, Zurich, etc. for the text. Do not use a fancy, calligraphic font. Use title case (similar to subheadings of this article) for the title and upper and lower case for the remaining text. Do not use capitals and italics as both these are difficult to read and takes more time to read. Italic and bold typeface may be sparingly used to highlight the text. Do not underline the text (the underline is very close to the descending letters e.g. ygqp). Keep the character spacing ‘expanded’ by about 0.2 to 0.4 point (e.g. abcdefg - is normal and abcdefg - is expanded by 0.4).
Font colour: Use a contrasting colour for the text as compared to the background (vide supra). The title font can be in a different colour than the rest of the text. Occasional important words or sentences may be highlighted in a different colour.
Paragraph format: Do not fully justify the paragraph – this leaves uneven spaces between the words and letters, making it difficult to read. Keep the line spacing about one and half times.
Write in phrases and not in sentences, except probably for the conclusions. Do not hyphenate words (keep automatic hyphenation off). Avoid abbreviations especially non-conventional ones. Avoid footnotes. Use bullets or numbers to highlight different points. Selective coloured strips or background shades can be used to highlight the text.
? Use no more than two different types of fonts
? Use no more than four different font colours
? Use no more than six lines of text per slide
? Use no more than eight words per line of text
A good presentation is an effective combination of verbal and visual elements. Illustrations help to explain concepts that cannot be verbalised. Use illustrations to hold the attention, clarify, restate, explain and interpret. A number of people suggest the following rule of thumb: ‘Never, without good reason, use more than two slides in a row with no pictures’. However, please note that overloading a slide with visuals is the most common mistake in slide preparation.
Charts and graphs
Simplify data: The audience should be able to absorb the point at a glance. Analyse the audience, reorganize the data, and decide the message to be conveyed. Change the format e.g. from a line graph, which is good for a printed manuscript, to a horizontal bar chart, the information from which will be easy to absorb.
Choose the right graph: The horizontal bar chart can be used for comparing items at one point in time; while for comparing parts of a whole– a pie chart is appropriate. For showing change over time, use the line charts (if more than four or five data points are to be presented) or vertical bars (if less than four data points are to be shown). For multiple comparisons, a segmented bar chart (with each bar representing 100 percent, and each segment a percentage of the whole) is the best option.
Make the chart easy to read: Use colour, shading, or arrows to highlight key words or concepts. Make the most important text largest, the most important data lines or sections darkest. Make bars and columns wider than the spaces between them. Avoid fill patterns, such as contrasting lines, wave patterns, and criss-crosses. Eliminate all unnecessary details, avoid grid lines, data points, boxes, etc. Label the X- and Y-axes and label the lines, bars, or pie wedges. Put the percentages inside the pie and the labels outside. Round off numbers in titles, graph labels, and axis labels. Start a numerical axis at zero. Try to keep the same scale and size on graphs of a similar type for an easy comparison.
While making comparisons within graphs, the contrast between two comparable points should be very distinct. Use contrasting colour, density (e. g. thickness of lines) and shapes (e.g. markers on the line graphs) for comparisons.
Choose the vertical axis scale carefully: Changing the scale can decrease the impact of an otherwise dramatic difference in the data.
All graphs and charts should be drawn for use in slides and not taken directly from a printed text, as the visibility and utility of printed matter is different from the one to be projected on a screen for 45 seconds.
Whenever possible, use graphs or charts instead of tables. If a table is used, only include the data that you are going to discuss. Numbers can be best compared if arranged in rows rather than in columns. Colours can be used to highlight different rows or columns. Use contrasting coloured numbers to highlight significant data in the tables. Use a leading zero while showing decimal fractions (Use 0.11 and not .11 as the latter can be mistaken for 11)
? ? Limit bar charts to 5-7 bars
? Limit pie charts to five slices
? Limit number of columns in a table to four and rows to seven
? Limit number of colours used in graphs and tables to 4-5
Using digital images in the slide
While scanning an image for full screen, scan the image at 480 x 640 pixels at 72 to 96 dpi. This size will fill the computer screen while maintaining a relatively small file size. If only a small picture is required, scan at 240 x 320 pixels at 72 to 96 dpi. Increasing the scanning resolution (e.g. to 300 dpi) will not improve the quality any further as 72 dpi is the optimal resolution for the monitors and projectors. Black and white photographs and radiographs should be scanned at greyscale. The scanned image can be imported in the presentation program as jpeg format or gif/tiff files. The jpeg format due to its ability to compress the size of the file and compatibility is very useful.
Patients’ identity should not be visible in photographs. Make sure that all the photographs have aesthetic looks.
? Letter height: no lettering less than six per cent of the longest dimension of the slide
? Letter thickness: no letter height more than six times its thickness
? Data content: no more than six times two (i.e. twelve times) the items of information
? Number of slides: not more than six in each quarter of an hour
? Colour: six percent of your audience is colour blind, use colours carefully
? Visibility: all visual materials should be legible at six times their diagonal dimensions
? When seen with naked eye, the slide text is equivalent to font size of six point
Slides can be simple yet attractive and unique. Most people use the readymade templates for slide background and over the years, everyone in the audience must have seen these templates somewhere or the other. Make your own background design. Have a customised template specifically for your presentations. Graphically rich backgrounds (subtly layered photographs, logos) and other original graphics relevant to the subject of the presentation will help to create unique presentations. Let your artistic skills show your audience the special thought that went into creating the slides.
One may use a simple word processor for text matter and take a printout for the slides. There are software programmes especially dedicated for presentations including Microsoft PowerPoint, Corel Presentations, Lotus Freelance, and Harvard Graphics. Simple graphics to be incorporated into the presentations can be made in Microsoft Photo Editor or any other simple software. For extensive graphic work, Corel Draw, Adobe Illustrator, Adobe PhotoShop, etc. can be helpful.
Film recorder: A 35 mm slide recorder, which can give output directly from a computer, will give the best results. One will need the help of a professional service provider for this.
Direct photography: Using a 35 mm single lens reflex (SLR) camera one can convert the computer monitor screen frames to a 35 mm slide. An exposure time of 1/30 second (ideal 1/1 second) is required. The camera needs to be steadied with the help of a tripod stand. The monitor should have a flat screen otherwise the curvatures of the screen will distort the image. Alternatively, one can reduce the size of the screen frame to fit just half of the screen and photograph only that portion of the screen. The monitor resolution should be a minimum of 800X600 and the colour setting High Colour (16 bit) or higher.
Using a printout: One can get the text material printed on a paper using a laser printer or a good quality DeskJet printer. The printed text can then be photographed to get a black and white or a diazo slide (with blue background).
Hand-printed slides: Hand printed slides prepared by stencils should be avoided in this computer era, if the slides can not be perfectly done it gives an impression that the presenter had no time to prepare the slides or the presentation is not worth his time. In both the cases he should have then avoided the presentation.
The slides are mounted on some stiffer material so that they can be projected. The mounts also allow better preservation of the slides. Glass mounts are the most expensive, but preserve the slides best and are easy to clean. Plastic mounts are the most commonly used, and are relatively inexpensive. Cardboard mounts are the cheapest, but are difficult to clean, and often get deformed and therefore get stuck in the carousel.
Hold the slide mount and not the slide film.
If there are fingerprint marks on the film side, they can be wiped off with carbon tetra chloride or a film cleaner. Dust can be removed with a dry air spray (used from a distance) or gentle brushing with a watercolour brush.
Hold the slide up to a light source; one side has less shine, the text is legible and the image is the right way around. Label the slide with a little red dot on the lower left - hand corner. Number every slide with a pencil on the opposite side of the red dot; these numbers can be changed if slides from different groups are used for one presentation. Run a permanent or fluorescent marker along the bottom of the mounts so that if the slides are mounted in the carousel, a missing marker will point out to a wrongly placed slide. An alternative method would be to mark all sides but the bottom, so if marker is seen when the slide is mounted in the carousel it implies an improperly loaded slide. Also, label the slides with your name and topic.
Prakash has discussed a simple and inexpensive method for filing slides that enables an easy retrieval. All the slides can be grouped in a few groups depending on the subject. Each group is assigned a colour code and each slide in that group is labelled with that colour (the lower left-hand dot can be of that colour instead of red). Then the slides are numbered according to a logical sequence. Slides are stored in plastic transparency holders with a written description of each slide. The transparency holders can be then filed in ring binders.
Store the slides in a cool, dark well ventilated place. Keep pouches of photographic silica gel to absorb moisture, which is the biggest enemy of slides.
Use carousels with capacity of 80 slides (the carousels with a capacity of 140 slides often tend to jam). Before loading the slides in the carousel, make sure that the slide mounts are not torn or bent. The slides should be inserted ‘upside down, emulsion-side toward the screen’ i.e. the marker dot should be on top and opposite the projection screen.
The projectors used in large halls have very powerful lenses and light sources that generate a lot of heat. Only glass- mounted slides will survive in this environment. The heat generated and light kills the slides, hence it is important not to project a slide for long time.
If a carousel gets jammed, there is a quick release lever at the centre. Alternatively, use a coin to release the slide.
Generally single projection avoids the need for the audience to switch attention from one slide to another and is preferable; however certain presentations can be facilitated by double projection. A slide with the outline of the presentation can be kept as a still slide on one side, if the talk is long or the subject is complex or subdivided into multiple headings and subheadings. Projecting two slides simultaneously side by side can also help to compare two concepts or images. When used for comparisons, care should be taken that both slides are comparable. If there is no matching slide on one side, a blank (a dark coloured slide) should be used.
Labelling of sets for double projection should be carefully done. Label all right sided slides with one colour and all the left sided ones with another colour. The carousels should also be labelled accordingly before handing them over to the projectionist. Both the slide carousels should move simultaneously. If the slide on one side needs to be projected for the subsequent screen also, use a duplicate slide.
? Select your slides only after the outline of the talk has been prepared.
? Always practice the presentation with the slides.
? The final slides should be made only after the speech for presentation has been prepared completely. This accommodates room for changes required according to the speech.
? Utilise the preview room to check the slides before presentation.
? Understand the working of the equipment to be used and test it well in advance to permit replacement of any or all of the pieces of equipment or slides.
? Avoid the recycled look– The ability to reuse slides is a prime reason for using slides. However, if you value your audience they should have a feel that the presentation was only for them. It is useful to develop a consistent style: i.e. same colour scheme and backgrounds – for all your presentations. This way, you will be able to mix and match slides taken from different presentations you have prepared over time, without the audience realising it.
? Duplicate slide: If the same slide is required at several places in a presentation, make a copy of the slide for each use rather than going back to the slide repeatedly.
? Blank slides: If the discussion at a particular point is beyond that presented in the slide, it is necessary that audience is not distracted by the matter on the same or the next slide. Project a blank slide of a subdued colour (dark blue or dark green) during this discussion.
? The last slide can be a black slide to avoid a glaring white screen coming up at the end.
? Acknowledge the resources; make sure you are not infringing copyright laws.
? Make back-up copies frequently and at least at two different places.
? As an extra precaution, leave the slide files on a server or mail it to your own web-based e-mail account for recovery from a remote site.
? Carry visual aids made in at least one more format: overhead transparency, flipcharts or floppies for LCD projector, especially when giving the presentation at an unknown place.
? Even with all precautions and back up you may end up giving the presentation without any visual aids, hence prepare for a ‘self-sufficient’ talk.
? Give detailed information on the equipment, availability of facility for double projection, back-up facility, preview room, time allotted for presentation, reporting time for presenter, etc.
? Good lighting is a must for a good presentation. There should be an unequal distribution of light– most light on the presenter, some on the audience and none on the screen. The audience should see as much of the presenter’s face as possible. Only two stage lights are sufficient to cross light the presenter effectively. Add a dimmer pack to adjust the light level so that the presenter can still see the audience while speaking and the audience can take notes. There should never be direct sun, incandescent, or fluorescent light on the screen.
? To determine how close the audience can comfortably be to the screen, multiply the width of the screen by two. That number represents how far the first row should be from the screen. The last row should be no farther away than eight times the screen width.
? Always have a back-up system. Keep an attendant to handle problems.
? If the facilities for double projection are offered, make sure that the screen is sufficient for double projection and that backup facilities are available for both the projectors.
? Do provide a slide preview room.
? Rather than having a second person to whom the presenter must constantly say ‘next slide please’, provide a remote control.
The authors are thankful to Dr Vinita Salvi and Dr SB Bavdekar for their valuable suggestions in preparation of the manuscript.