Photos & Graphics: Selecting & Preparing Images for Your Presentation
- Feb 19, 2007
KNOWING WHAT TYPES of images to use and how to make them motivate, educate, and stimulate your audience is a powerful weapon to have in your arsenal. We’ve all suffered through unimaginative presentations with mismatched clip art and poorly handled photos. The end result is usually an audience that walks away missing the point or is simply too bored to care.
Raster Versus Vector
There are two major categories of graphics—raster and vector. Knowing the difference (as well as the pros and cons of each) will help you make smart choices. In a nutshell, here’s what you need to know.
Raster graphics are generally built with a matrix of picture elements (pixels). Raster graphics (also called bitmaps) generally describe those images that originated from sources like digital cameras, scanners, or screen captures. They are well suited for photographic images. There are several formats for raster graphics, including Windows Bitmap and JPEG.
Vector graphics are created by using points, lines, or other geometric objects. A vector graphic can generally be scaled to a very large size with no loss of quality. Additionally, the files usually require very little disk space. Vector graphics are well suited for illustrations, and usually they will retain their shape and transparency when imported into PowerPoint. Graphics with transparency will allow the background of your slide to show through. Typical formats for vector graphics are .wmf and .eps.
Making Clip Art Your friend
Ask a designer to incorporate clip art into a design and it might induce a gag reflex. There is good news however; clip art has come a long way, and if you know how to find the good stuff and use it properly, you can take an ordinary presentation and make it look posh and sophisticated. PowerPoint includes a large library of clip art to choose from as well as a series of AutoShapes that can turn a hard-to-follow concept in to a visual a-ha! Being able to guide your audience with visual clues can reinforce your objectives as long as you know how to use them, when to use them, and which ones to use.
Using Photos in Your Presentations
With the prevalence of affordable high-quality digital cameras and scanners it is easier than ever to integrate photos in your presentations. PowerPoint gives you a wide array of tools to compress, resize and manipulate photos; giving you the power you need. With all that power comes great responsibility. Learning how to optimize your photos for portability and performance will make your presentations run better on a variety of different systems and allow you to be able to e-mail documents that once could only be burned to a CD.
Understanding File Formats
As you work with digital photos, clip art, and graphics from the Internet, you’ll come across a lot of different image types. Several different file formats have been created for both special purposes and licensing reasons. Without any additional work on your part, Microsoft PowerPoint 2007 recognizes the following options.
Windows Metafile (.emf or .wmf)
This file format is a proprietary one made by Microsoft for use throughout their software products. You will find it commonly used in the Microsoft Clip Organizer for illustrations. The .wmf file type was introduced first and supports 16 bits of information. The .emf file format (also known as enhanced metafile) is newer, and supports 32 bits of information for higher visual quality.
Windows Bitmap (.bmp, .dib, or .rle)
This file format is commonly used by Windows and is generally very compatible across applications. A disadvantage is that the files are typically not compressed, which can result in a large file size. When PowerPoint gets to a slide with graphics on it, it must cache the graphic. This can result in delays during your presentation when you’re clicking to advance slides. Most users prefer to work with compressed formats like JPEG when they need to insert photos.
Computer Graphics Metafile (.cgm)
The use of CGM files became a standard in 1987, they can be used for both vector and raster graphics. It is not widely supported for use on the Internet, but is more prevalent in technical fields like engineering. You may likely encounter it as well for military uses. CGM files generally are small.
GIF—Graphics Interchange Format (.gif)
The GIF format (pronounced gif or jif) is a very common Web format. It was originally developed for use in the CompuServe online service. The files are limited to a maximum of 256 colors (referred to as a bit image). This limit of colors can reduce file size, but can be problematic for photos. Users will choose GIFs for two primary reasons: the need for embedded transparency (such as in a corporate logo) or for basic animation.
JPEG—Joint Photographic Experts Group (.jpg)
The JPEG format is used to optimize large photos for multimedia use, such as the Internet or a slide presentation. The format uses lossy compression, which means that data is permanently thrown away to reduce file sizes. Most point-and-shoot digital cameras also use JPEG images. The JPEG format is best suited for images with many colors, such as photographs. But keep in mind a JPEG file suffers quality loss every time it is modified and resaved. Many professional image editors will wait to create a JPEG file until they have completed their image-editing tasks.
PNG—Portable Network Graphics (.png)
The PNG file format merges the best features of JPEG and GIF files. It allows for a 24-bit image (millions of colors) plus embedded transparency. While not all Web browsers support it (notably older versions of Internet Explorer) it is a standardized Web graphics format. PNG graphics are well suited for presentations, especially if you need embedded transparency.
PICT—Macintosh PICT (.pct)
This is the original image format used by Macintosh computers (pre-OS X). It can be used for both raster and vector graphics. This format will likely be encountered if you are working with an older PowerPoint presentation created on a Mac. While the format is widely supported, it is becoming less common.
TIFF—Tagged Image File Format (.tif)
The TIFF format is commonly used for high-quality printing. It can store up to 48 bits of color information, making it very accurate. TIFFs can be quite large is size, but they do support compression to reduce the size of the file.
Vector Markup Language (.vml)
Vector Markup Language (VML) is based on an XML exchange. It is an emerging standard and is supported by newer Web browsers. The standard is being pushed by Microsoft and the W3C, the standards setting consortium on the Web.
There are many other file formats that you’ll likely encounter, especially if you work with graphic professionals or Adobe applications. You have two options to work around unsupported image formats.
The first is to use the Microsoft Clip Organizer to import and convert the files. You can access the Clip Organizer by selecting the Insert tab then clicking the Clip Art button. The Clip Art pane opens to the right of your slide. Click the Organize clips button at the bottom of the pane to open the Microsoft Clip organizer. Microsoft installs several filters to convert images to acceptable formats for use in Microsoft Office.
If the Clip Organizer cannot import the image, then you must use another piece of software to convert the images. Nearly every other software shares file formats in common with PowerPoint (especially JPEG files). You can go back to the original application (or the image creator) to get another file. If that doesn’t work, then download an affordable image converter like Irfanview (www.irfanview.com) for PCs or Graphic Converter (www.lemkesoft.com) for Macintosh.