As any jobbing landscape photographer worth their salt knows, you need to shoot both horizontal and vertical variations of a scenic shot to make your images more saleable – a traditional landscape-orientation shot makes for a fantastic opening spread in a magazine or header image on a website, while a portrait-orientation image is the one that picture editors will select for the cover or a full-page photo.
However, it's not as simple as unlocking your tripod head and allowing the camera to drop by 90 degrees; this moves the camera off-center and down by an inch or so, ruining your carefully aligned composition, in addition to throwing the center of balance from above the tripod, destabilizing your whole setup.
