Keep the photo framing intentional
The starting portrait canvas is 4:5. A wider source leaves white space in Full photo mode; Fill page fills the canvas but crops its edges. Compare the preview with the original before saving, especially when a face or label is close to the frame.
Four rows and four columns divide the canvas into sixteen areas. On a rectangular canvas these cells are rectangles. Choose a square canvas and equal counts when you need square cells, rather than stretching a portrait to force the result.

