Size, length and backgrounds
The video's shorter side is at most 1080 pixels and never larger than your biggest photo, so small scans do not become a soft, oversized file. One slideshow holds up to 200 photos and runs up to 10 minutes.
Portrait photos in a wide frame, or wide photos in a tall one, leave empty space. Choose how to fill it: a blurred copy of the photo, black or white. ToolGPT can show one shape with all three backgrounds so you can compare them.