Aspect ratio decides what shape the canvas is. Landscape 16:9 owns projectors and streams, 9:16 owns phones and reels, 1:1 survives in feeds, and stage LED often ignores all three with strips and towers built to the set design.
Content survives ratio changes badly: cropping beheads composition, stretching announces amateurism. Serious visual systems compose per ratio instead, keeping energy centered where every crop preserves it or reframing outright.
Photism bakes the reality in with a frame control that cycles full, 16:9, 9:16, and 1:1, so a set can be performed to the room and clipped for the feed without post-production surgery.