First off, do you even need to compress your photos?
If not, don't bother (you're welcome)!
But if you find that your presentation is running slow, or if it's too large to share with the people that need it, then here's how to reduce your presentation's file size.
Depending on the number of photos in your presentation and how you compress them, you can reduce the size of your presentation by 80%.
How to compress images in PowerPoint
Select the image you want to compress, and then:
- Go up to the Picture Tools Format tab
- Click on the Compress Pictures command
- Select your Compression options (see image below)
- Select your Resolution (see image below)
- Click OK
Your two compression options are EXTREMELY important, so make sure you understand what they are before you move forward.
Apply only to this photo
This is an important option to understand before you accidentally mess up all of the photos in your presentation.
Apply only to this photo (the default setting) ensures that only the picture you currently have selected is compressed.
No other images in your presentation are affected (hence why this is the default option).
By unselecting this option, you are telling PowerPoint to compress all of the photos within your presentation based on your selections.
This can save you a bunch of time if you know what you are doing, and you know that you want all of the photos in your slides compressed in this way.
BUT this can waste a bunch of time if you don’t know what you are doing.
If you catch the mistake immediately, you can hit CTRL+Z to undo your compression. Otherwise you’ll have to hunt down an earlier version of your presentation or start all over with the original photos again.
Delete cropped areas of pictures
This option affects whether or not PowerPoint keeps the cropped areas of your photos.
When you first crop a photo down, PowerPoint keeps the part that you crop (it just hides it from you). That’s why cropping an image doesn't actually change the size in PowerPoint.
If you know that you do not want keep the cropped areas of your photos, you can decrease the overall size of your image by selecting the 'Delete cropped areas of pictures' compression option.
Just be warned, that once you delete the cropped areas you cannot undo them later. You’ll have to start over with the original photo.
When choosing a resolution for your photos, it’s important to keep in mind the lifetime of the presentation you are building, and how it will be used.
Beware of choosing a lower resolution during the draft phase of creating your slides simply to save space, as you will find that you cannot undo the lower resolution before your big pitch.
It might be hard to tell in the photos below, the but picture compressed to 96 ppi is extremely grainy along the edges of the building and would show poorly on an overhead projector.
Higher resolutions like HD 330 ppi (pixels per inch) equate to the highest quality photo with larger file sizes.
Lower resolutions like email 96 ppi (pixels per inch) equate to lower quality photos that can appear grainy on large overhead projectors, and thus smaller files sizes.
If your presentation is a live event, such as a Ted talk, or if it will be run on a large HD monitor, then you’ll want the highest resolution photos as possible throughout your slide creation process.
If you are simply emailing a presentation to a colleague to view ONLY on their laptop (it will never be presented on a large overhead screen) then you can get away with a much lower resolution.
How much does resolution affect image size?
In the photo above, I’ve added a single image to a slideshow and used the various compression options so you can see how much it affects the size of the PowerPoint presentation.
Note that in this case, the 330 ppi and 220 ppi image resolutions result in the exact same image size.
This is something you’ll have to play around with.