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PowerPoint presentations are a valuable tool for educating the public
about invasive plants. The files can be downloaded and used by educators
in group settings or simply viewed by people wanting a better understanding
of invasive plants. Photos and graphics enhance the presentations, reinforcing
the message of the presentation.
In order to use PowerPoint presentations on the web, it is important to
minimize the file size to decrease the download time and save space on
the server. There are two aspects to accomplishing this: minimizing image
size and bypassing the template features.
Generally, photos are digitized at a resolution of 300 dpi (dots per
inch) or more. The newer digital cameras frequently create huge image
sizes due to their high resolutions. This is great for print media, but
images intended to be viewed onscreen should be no more than 96 dpi (72
dpi is a common default size). The eye cannot perceive resolutions greater
than 96 when viewed onscreen. Many graphics designed for printing are
also very large files and need to be reduced.
The file size of your PowerPoint presentation can be roughly estimated
by adding up the file sizes of the images in the presentation. If you
have 20 images that are about 100 KB in size, your file size will be at
least 2 MB. If those same 20 image are 800 KB, the file size is at least
The usual file formats for the web are JPEG (or JPG) and GIF. Do not
use bitmaps (BMP) since they cannot be viewed from a browser without special
software. TIFF format are usually (but not always) too large. JPG is best
for images with many colors. GIFs are used for fewer colors or when a
transparent background is needed. Do not create too many incremental copies
if your file is JPEG. Each time you copy a JPEG, resolution is lost and
it starts to look fuzzy. This is called the lossy effect. GIF files are
lossless and do not lose resolution
In order to change the size of an image, you need to have some sort of
image editing software. Common choices are: Adobe PhotoShop, Macromedia
Fireworks, Kodak Imaging, or other software bundled with cameras and scanners.
Follow the instructions included with your software for Resizing. Always
save your original image and create a copy when resizing. Sometimes changing
the resolution is a separate operation from changing the image size. In
these situations, when you reduce the resolution without changing the
image size, the program compensates by increasing the size of the image.
Suddenly, your 4x6 image is 22x30 inches. You must go back in and reduce
the file size to about 6 x 9 inches for a full PowerPoint page.
Note: Simply resizing a photo from within PowerPoint does not
change the file size. In fact, the file will be larger because PowerPoint
keeps track of the original image size in case you want to go back to
Microsoft attempts to make its software easy to use. In PowerPoint, there
are several slide templates to make creating the presentation less time-consuming.
However, there is a price paid in file size if you use these templates.
Use Design Templates with caution. A PowerPoint (Office 2000 version)
file with one blank slide is 8 KB. The same blank slide with the Strategic
Design Template is 156 KB! Multiply that by the number of slides in your
presentations. This difference varies depending on the template used.
Using the Soaring template, the file is 22 KB.
Make sure you save the file under the correct version of PowerPoint.
Saving under a previous version can increase the file size geometrically.
For instance, the Strategic Design Template file from above, saved as
a previous version, is 2,396 KB!
In some versions of PowerPoint, the file size increases with the use
of the layout templates (those are the ones with text boxes and image
placeholders already arranged for you). Do not use these unless your slide
exactly matches the template. Use a blank slide instead.
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