For many of us Powerpoint and other types of presentation software have become vital to accomplishing our professional goals. Because of its ubiquity, there are piles of advice sites out there which discuss the proper ways to utilize this powerful tool. Rather than walking you through a list of tips about font size, wordiness, background color, and pointless animations, I wanted to focus this post very narrowly on the subject of using images in Powerpoint slides. Users of other presentation programs like Open Office’s Impress or Mac’s Keynote should note that all of the advice included in this post applies to those programs as well.
For the most part adding images to your presentation is desperately easy. If you’ve done any work at all with these programs, you almost certainly know that you can add an image using the “insert” feature. Once the image has been placed on your slide, you can drag it to any location or alter its size by clicking on it and dragging the sizing handles which appear at its edges.
What even the seasoned presentation maker might not know is why some of your images look fine on your computer screen but look terrible when displayed on the projector. I recently attended a job talk where the candidate repeatedly apologized to the assembled crowd because their view of his images wasn’t nearly as crisp as what he was seeing. Of course, this isn’t seen as a cardinal sin of making presentations. It’s merely viewed as an unfortunate limitation of our technology. I’ve made that very same apology to students when showing images as a lecturer or in discussion sections. That said. You can avoid this presentation pitfall in the first place.
Image Resolution Is the Key
Most projectors installed in college classrooms as well as the smaller portable ones used in conference rooms project their images at a resolution of 1024 x 768 pixels. Because the machine is transmitting at that resolution, an image of that resolution can be shown across the full screen without much loss of quality. If you aren’t sure of the resolution of your image, simply right click on the file and view its properties. Alternately, many photo viewing programs will show you the details of the image, including the resolution, somewhere on the screen. Images with resolutions larger than 1024 x 768 will generally also project clearly.
For images at or above this key resolution, you should be able to reduce the display size (how much of the slide the image covers) without any loss of image quality. When resizing, however, be sure to click and drag the images at the corners so that you maintain the original shape. Pulling one of the sizing handles at the side, top, or bottom of an image will alter only one dimension (length or width) and the other won’t correspond.
Images with smaller resolutions shouldn’t be made to fill the full screen. They will distort and blur. I think this is where most of us go awry when adding images to slides. Also, the effect of this distortion is more pronounced in the projected image than in the one you see on the screen of your computer. This is because your computer screen is likely set to a different resolution than the projector. You can use the 1024 x 768 resolution numbers as a rough guide to know how large you can display an image in Powerpoint. For example, an image with a resolution of 512 x 384 pixels (half of the projector’s resolution) would look good taking up about half the screen in a presentation slide. Stretching it any larger will cause distortion.
Finding Images of the Proper Resolution
If you are a including your own images in a presentation, then you should have no trouble controlling the display resolution. If you are combing the net for slide content, however, you’ll need to be much more vigilant. The fine folks at Google provide a convenient set of “size” options along the side of their image search page. Bing’s image search offers a similar option. At Flickr there isn’t a way to search by size. However, available size options are presented once you’ve selected an image. Finally, at Wikimedia Commons, an excellent resource for media free from copyright restrictions, image resolutions are listed below each thumbnail along with other image properties.
Other Image Advice
- Use clear, crisp images. If your image looks washed or pixilated on your screen, it will look much worse on the projector’s screen.
- Be aware of any copyright issues connected to your use of images. Most classroom uses fall under the fair use rules but there are exceptions and pitfalls. Check your institution’s copyright policy statements for details.
- Ambient light is the enemy of projector clarity. Seek the golden balance between having it dark enough at the front of the room so that the projected image is clear and having enough light for your viewers to take notes easily or simply remain conscious.
- Avoid images with small details. Even though the projector may have made the image eight feet tall, you need to remember that your viewers are usually sitting anywhere from 10 to 100 feet away from the screen. Images with small, unclear text or details won’t go over well.
If you’ve got advice on this topic, share it with us in the comments below.