Here is a slide appearing in 4 of every 5 conference presentations. If you've seen any Science By Powerpoint it should look familiar:
It's the slide with bullet points and a tiny image in the corner.
Some talks consist entirely of this format, repeated 30 times over. The text and images change of course, but all are basically the same. Images I squint at to see properly next to the speaker's notes.
This arrangement is counterproductive. If the point of including an image is to communicate more effectively, why make the audience work harder by presenting an image too small to process? And why make the audience choose between looking at an image and reading bullet points?
The solution is simple: display the image at full resolution on its own slide. If you've got beautiful photos, make the most of them.
Splitting a slide into two or three need not add time. Good images are powerful precisely because our brains process them effortlessly. They require little additional verbal explanation. And a few seconds is all the audience needs to ingest them- the speaker can continue talking before advancing to the following slide.
So let the image stand by itself, full screen.