Files sizes can quickly get out of control in Powerpoint files, especially when high-quality images and logos are included.
The file size of documents we simply present on a screen is seldom an issue; however if you plan to send, or post, heavily-branded files there is a cost with respect to email bottlenecks and memory limitations on handheld devices.
So it’s important to understand how to optimize the way your images are stored in Powerpoint, and take advantage of the built-in tools to compress the ‘heavy’ images so they travel well.
You’ll want to test several different levels of compression, to see the impact on quality (smaller file = lower-quality images). But a file intended to be shown only on a screen does not have to be built with the same resolution as a file being sent to a professional printer for magazine-quality output.
- When you crop an image, the ‘hidden’ parts are still stored in the file.
- When you resize an image, the original data that makes up that image is not changed (or reduced).
When you understand these two ideas, the two ways to making the file smaller begin to make a lot of sense. What we want to do is:
- Throw away the portions of images we have ‘cropped’ off; why store what we aren’t using?
- Store images only at the resolution they need to be at, to display at the desired quality. So, an image that was originally 300dpi, then shrunk in dimensions in Powerpoint, is likely carrying a lot more data than is necessary for your intended audience.
So, how much do we throw away? That depends on the destination of the file. Powerpoint provides several levels of compression: 96dpi, 150dpi, 220dpi, 330dpi, and a fifth option that does not alter the compression — but only throws away those cropped portions of images you didn’t want to see anyway.
Here are Microsoft’s instructions for picture compression in Powerpoint:
“Reduce the file size of a picture” (microsoft.com)
Before you do this to all of your presentations, it is recommended that you make a backup of the original file — because once you use this feature, your images will not include cropped portions, or be at their original resolutions any more; so if you intend to make drastic edits to your design, you’ll probably want an uncompressed, full-resolution version to work from.