PowerPoint File Sizes

I've been creating a lot of PowerPoint presentations from scratch for my new course, and have been trawling the web and my various media CDs for good visual supplements. Recently I discovered that I could just click and drag images straight from web pages and the file explorer into PowerPoint, which I was quite pleased about since it saved me a lot of clicks.

Unfortunately, my new image-heavy presentations were getting large. And not just "oh, it won't fit on a floppy anymore" large, but LARGE. One presentation was 70 MB, and another swelled to 95 MB. The 70 MB file was somewhat understandable, as it had more than 80 slides, and almost every slide had at least one image (though they were all small jpg's to begin with). The 95 MB file was ridiculous, however, as I had only added 21 images, and I knew for a fact that all of the images were either jpgs or gifs that were less than 200 KB to begin with.

A few quick searches on Google found the solution (on a Microsoft page, no less). Apparently inserting images by dragging or pasting them onto a slide can automatically convert them into wmf (Windows MetaFile) format, which sounds suspiciously like it has about as much compression as a bitmap.

To rectify the swollen file size, the Microsoft page suggested copying the images from the within the PowerPoint file and then doing a "paste special" as jpgs, to convert the images to jpgs. I tried this and the pasted images were not as crisp as the originals, so I went back and found the original images (I always include the source URL of the image on its slide as a reference), and reinserted them all using "Insert / image from file." After doing this the file had the exact same images with the exact same resolution, but the file was 1.8 MB instead of 95 MB.

What a difference a picture insertion method makes.