"If I had to choose, I would rather have birds than airplanes." Charles Augustus Lindbergh
Life is full of choices. You even have choices to make when you are using use PowerPoint presentations with web conferencing technology.
In this article I will discuss some background information on Internet bandwidth and image resolution and then talk about the options available to you.
Internet bandwidth, or Internet speed, is the size of the "pipe" available to transfer data from one computer to another computer over the Internet. As an analogy we could look at filling a gallon bucket with water. If we needed to fill the bucket and we had a half inch pipe, it would take about thirty seconds. If we had a two inch pipe it would take about two seconds. The bigger the pipe the faster we could complete the task. Engineers talk about Volume Flow, measured in gallons per minute, to describe the volume of water that can be moved from point A to point B. We use the term Kilobits Per Second (kbit/s) to specify the volume of data we can move from one computer to another. Dial-up services typically provide up to 56 kbit/s - a small pipe, while ADSL and Cable services are up to a hundred times, or more, faster - a big pipe. To put that in perspective, it would take approximately four and half minutes to download a two megabyte file on a dial-up connection. The same file will download in about five seconds with a high speed ADSL or Cable connection. Some providers offer a "Lite" ADSL or Cable service that is five to ten time faster than dial-up. The download times I have suggested above are the theoretical best. Internet congestion, the physical quality of the connection, and other factors will degrade the service so and therefore the performance will be less than perfect.
Image resolution refers to the sharpness and clarity of an image. In the case of a printer the resolution indicates the number of dots per inch (dpi). For example, a 300-dpi printer is one that is capable of printing 300 distinct dots in a line one inch long. A photograph, whether viewed on the screen or printed, is composed of tiny dots - also called pixels. The number of these dots that fit into a one inch space specify the resolution - the higher the number the sharper the image resolution but also the need for a larger file and the longer to send the image to another computer. For a display, the screen resolution signifies the number of dots (pixels) for the entire screen. Therefore you will see a display with a resolution of 800 x 600 - 800 dots across the top and 600 dots vertical - or 1024 x 768 and so on.
One important point to recognize is that a 17 inch display with a resolution of 1024 x 768 has a dpi resolution of about 80. Therefore any image with a resolution more than 80 is wasting Internet bandwidth if is only sent to be viewed on a display.
PowerPoint is an excellent tool for creating powerful presentation material. The slides created with PowerPoint may contain many different types of objects such as text, images and so forth. Because some of these objects, i.e. images, can be very large, care must be exercised when the presentation is distributed via the Internet. PowerPoint version 2002 or newer provides a formatting function to compress a single image or all the images in the presentation to a resolution of 96dpi - a value suitable for Internet use. To use this function select any image, click the Format/Picture menu, click Compress and follow the prompts. Make sure you select the "Compress All Images" option.
PowerPoint is designed to be used directly from a Computer. It does not work well in its native state when pushing slides in a web conference environment. However the web conference technology provides a utility to convert the presentation into HTML, GIF or JPG formats, all suitable for web conference use. The same utility, found in Administration/Document Center, will upload the presentation to a web space so it can be used in a web conference meeting.
The obvious question is: "What format should I use?" I will start with the simple answer first. If you are going to use the presentation slides with the Whiteboard, also provided with the technology, there is no choice. It must be converted to JPG or GIF format. Choosing GIF or JPG is a matter of personal preference. Also if you are going to use the uploaded presentation outside of the web conference room with any browser other than Internet Explorer, you should use the JPG or GIF option.
If the presentation is only going to be used as a web presentation you may choose the HTML, JPG, or GIF formatting options. Your objective should be to make the PowerPoint converted files as small as possible while maintaining highest quality presentation. Remember you are going to push these slides to your audience as well as be speaking to your audience at the same time. Both the audio and the pushed slides will require bandwidth. If you are sending a large image file it will take some time to push that file, particularly if you or any of your audience is using a dial-up connections, and more importantly the audio quality will be negatively impacted due to the imposed delays.
If you have a version of PowerPoint that will compress the images, I would recommend you compress the images, save the presentation and choose the HTML formatting option. It is my opinion the resulting conversion, except for rare occasions, will have the optimal file sizes and will certainly look more professional.
The following example will show a presentation slide that was converted using the HTML format. The file size is 40K. Click to view After viewing, click the Back button on the browser to return to to place.
The following example is the same presentation slide that was converted using the JPG format option. The file size is 58K. Compare the text at the bottom and top of both examples. Click to view After viewing, click the Back button on the browser to return to to place.
In this case the HTML converted document is superior, smaller in size, better quality and there therefore the better choice.
If you have a older version of PowerPoint you could use an image editor to change the resolution of images before you insert them into PowerPoint or if you don't wish to do that, use either the GIF or JPG formatting option.
I would strongly recommend that you experiment with the different options and choose the option that works best for you.
