Midjourney Aspect Ratios: The One Setting That Keeps My Prints From Blurry
Wrong --ar means a crop or an upscale that falls apart at print size. Set it before you generate, not after.
I generated a square hero, loved it, then needed it as an A4 poster and the upscale turned to mush because the original had too few pixels for the crop. Midjourney's --ar flag decides the canvas shape before the model draws, and that shape is your print size.
Rule I use now: know the final frame first. Poster? --ar 3:4. Banner? --ar 16:9. Square post? --ar 1:1. Setting it after means regenerating, because changing ratio later just crops the thing you liked.
Resolution follows from ratio. A portrait at 3:4 upscales cleaner than a square stretched tall, because you're not inventing pixels the model never made. The blur I fought was me asking the upscaler to draw what wasn't there.
It's a one-word habit that saves a redo every time. Pick the ratio from the destination, not from what looks good in the preview.