Wednesday, 26 March 2014

Using Camera Movements in Architecture Photography - Shift Movements

View cameras have a simple yet very effective design consisting of two standards mounted on a rail. The front standard holds the lens panel and the rear panel holds the film. A set of flexible bellows connects both the standards. This versatile design makes possible many types of movement of both the standards to achieve a wide variety of optical effects.

View Camera
View Camera

We can broadly divide the movements possible on a view camera into two; Shift movements and Scheimpflug adjustments. In this article we will discuss Shift movements and what it does to the image in detail.

Shift Movements

Shift movements are parallel movements of the front or the read standard in vertical or horizontal direction. Shift movements could be further divided into two categories; rising shifts and cross shifts.

Rising Shifts

Rising Shift Movement
Rising Shift Movement

In the illustration given above the image circle formed by the lens on the sensor plane is shown, (notice that the image is inverted). The first illustration shows how the frame could be captured with the lens in the normal/neutral position, we could see that this framing includes excessive amount of foreground and still the top of the building is cropped off. The next illustration shows the result of a rising shift, now the top of the building is inside of the area captured and we have eliminated the unwanted foreground.

Vertical shift movements (parallel movement of the lens plane in respect to the sensor plane) help architecture photographers eliminate the problem of converging verticals caused by tilting the camera up (mainly during exterior work) and also diverging verticals caused by tilting the camera down (mainly during interior shoots). In rising shifts the lens plane is shifted either up or down from its central (neutral) position. Shifting the lens plane up is also known as rising front and it helps avoid tilting the camera up (you can now include tall buildings in the frame just by using rising front movement keeping the sensor plane parallel to the subject plane). Similarly shifting the lens plane down is known as drop shifts and helps keep verticals straight without having to include too much ceiling or the need to photograph from very low angle.

Cross Shifts

Horizontal shift movements (parallel movement of the lens plane in respect to the sensor plane) help architectural photographers control perspective.

Using Cross Shift Movements for Exterior Shots

 While shooting exteriors cross shift help photograph a straight on view of the building while the camera is actually positioned on to one side of it, helpful when the viewpoint directly in front of the building is restricted. You simply line up the camera parallel to the front elevation of the building and employ cross shift instead of turning the camera thus preventing any perspective distortion.

Another important use is to control the perspective of the receding building when photographing a building at an angle from a relatively close vantage point using a wide angle lens. Turn the camera to make the angle to the building less acute and use cross shift movement to bring the building back into view. This creates a somewhat flattened perspective by expanding the area of front elevation visible through the lens.

Another use of cross shift is to create perfectly aligned panoramic shots. Place the camera on a tripod and take a series of shots applying cross shift movement in increments facilitating a minimum of 25% overlap between frames. It could be from extreme left to extreme right or from extreme right to extreme left. Using cross shift movement instead of simply turning the whole camera and lens setup avoids any parallax error and creates perfectly stitchable panoramas.

Using Cross Shift Movements for Interior Shots

While photographing interiors cross shifts help prevent converging of parallel horizontal lines. The secret to keeping parallel horizontal lines from converging is to keep the sensor plane horizontally parallel to the back wall.   As soon as the sensor plane ceases to be horizontally parallel to the back wall in a rectangular interior, the horizontal lines of the far wall in the picture will start to converge or diverge as a result of natural perspective.

Cross Shift Movement
Cross Shift Movement

The first illustration show how a fixed lens captures the scene, as the sensor plane is not horizontally parallel with the back wall of the room, horizontal lines of that wall converge. The second illustration shows how the room can be captured by using a cross shift movement of the lens allowing the sensor to remain parallel to the back wall thus keeping lines parallel.

Another use of cross shift movements in interior work is to correct the geometric distortion in objects that are in the foreground when shooting with a wide angle lens. The trick is to compose the frame with the foreground object directly in the center and use cross shifts to compose the frame with the object to the side instead of turning the camera. This will help minimize the distortion because our subject is in the center and distortion is greater as the subject is further from the central optical axis of the lens. Had we turned the camera to get the subject off center instead of employing cross shift we would have much more distortion in our image.

One technique that is impossible without camera movement is to photograph a mirror or any shiny subject from a parallel/head on position without having the image of the camera reflected in the surface. With camera movement we could simply place the camera to the side of the mirror and employ cross shift to include the mirror. Now the camera will not be reflected in the mirror as it is not directly in front of it.

It is even possible to combine both rising and cross shift movements of the front and rear standard within the limitation of the lens (Refer the article Lens Coverage for more on this) to achieve the exact framing required. In the next article we will discuss the second type of movement possible with view cameras - Scheimpflug adjustments.

Related Reading

  1. The Need For Camera Movements in Architectural Photography
  2. Architecture Photography Tips - Practical Lens Testing
  3. Lens Distortion
  4. Lens Aberrations
  5. Choosing Lens for Architectural Photography – Aperture, Speed and Performance