The illustration you added to a slide looks grainy, its shape is distorted, or the file has grown too heavy to email. When making slides, most stumbles are size problems. Here are the constraints particular to slides. Which pages to put pictures on, and how, is compared with real sample slides in “Illustrations in training slides work best on the right pages”.
Know how big a slide actually is
PowerPoint and Google Slides default to 16:9 widescreen, equivalent to about 1280 × 720 pixels. Older decks and some meeting-room projectors use 4:3. So even an image spread across the whole slide only needs around 1280 pixels. Huge photo-editing-sized images are unnecessary.
How much resolution you need
A useful guide is one to two times the width you want it to appear at on the slide. For half the slide width, around 700 pixels is enough; spread across the whole slide, around 1300.
However, if the deck will be printed and handed out, allow for double that. What is enough on screen looks grainy on paper. For print, 2000 pixels or more across the whole slide gives you a safe margin.
Do not stretch out of proportion
Drag the handle in the middle of an edge to make an image fit a box, and the aspect ratio breaks. People get wider or thinner, and round things become ovals. Below is the same picture placed with its proportions kept, and stretched to fit a square box.
To resize while keeping the proportions, drag a corner handle. If the box shape really does not fit, trim off the excess with “Crop” rather than stretching.
Do not enlarge small images
Blowing up a small image blurs the edges. If an image you inserted turns out smaller than you expected, looking for a larger original is more reliable than scaling it up.
Watch the file size
Insert several high-resolution images and the file can grow too heavy to attach to an email or share. PowerPoint has a feature for compressing pictures, so running it once before you distribute the file is the safe course.
Watch the format too. Older versions of PowerPoint cannot insert WebP. How to convert is covered in “What Is WebP? What to Do When a Downloaded Image Will Not Open”.
About Visual Hub assets
Our assets come as squares (1024 × 1024) and landscape (1408 × 768). A landscape one exceeds 1280 pixels even spread across the whole slide, so it is enough for presenting on screen. If you use one across a whole slide in a deck that will be printed and handed out, bear in mind that it falls short of the guide above.