Trapezoidal image distortion when camera isn't parallel to subject plane — far edges compress. Shift lenses or digital correction in post solves it.
The camera is tilted relative to the building, and the vertical lines converge towards the center of the frame — this is keystone distortion in everyday use. It occurs because the film plane is not parallel to the subject plane. If you look up at a facade from below, it appears trapezoidal: the top edges narrower, the bottom wider. The effect is optically unavoidable when the camera and subject are not oriented on the same plane.
On set, you have two ways to deal with it. The first: Shift lenses — specialized optics that shift the image plane without moving the entire camera. A 24mm or 45mm shift lens allows you to stand perpendicular to the building but shift the lens upwards until the facade fits completely into the frame. The vertical lines remain parallel. Shift lenses are precise but expensive and require experience — the focal plane changes, and exposure becomes tricky. The second way is less invasive: you accept the distortion on set and correct it in post-production. This saves time and equipment stress but costs pixels.
In post-production, perspective correction tools are used — in DaVinci Resolve, Nuke, or Adobe Premiere, the corners of the image can be individually manipulated to transform the trapezoidal shape back into a rectangle. The price: the image is cropped, and the resolution decreases. With 4K footage, this is manageable; with HD, it becomes tighter. Some DoPs deliberately accept the distortion because it adds dynamism to the image — especially in wide-angle shots of architecture or in psychological moments where a skewed perspective creates tension.
The decision is made before shooting begins: If you want to work with shifts, plan your units accordingly and inform the grip department. If you plan to correct, brief your colorist — they need to set metadata and ensure the correction remains consistent. Keystone distortion is not a mistake but an optical reality. Ignoring it or embracing it — that is design.