Perspective control describes techniques used to correct the problem of "converging verticals", which occurs principally in architectural images. There are basically three options:

• Change the angle of view, usually by utilizing a telephoto lens from a more distant viewpoint, or by finding a high viewpoint approximately half the height above the ground of the top of the structure being photographed. This might be achieved by getting permission to climb to the roof of a nearby building, or by taking the photograph from a helicopter or other aerial platform.
• Use a perscpective control (PC or "shift") lens. This is the best approach although also the most expensive in terms of photographic equipment. Such lenses cost in the region of £1,000 - £1,500.
• Photoshop has a special feature for correcting converging verticals among the Transform menu options. This allows any image to be corrected for perspective errors and consequent converging verticals.