Saturday, 5 April 2014

Controlling Perspective in Exterior Shots Using Focal Length

In the previous articles we have discussed the other two important elements in architectural photography composition namely Structure and Line Dynamics. It is now time to move on to the third element that is Perspective. We have divided this topic into two articles, one that deals with controlling perspective in exterior shots and the second part which deals with perspective in interiors.

Perspective In Exteriors

While photographing exteriors of buildings it is important to capture the three dimensional nature of the building and not just feature it as a facade. Contrast, tone and line dynamics all play their part in producing an illusion of depth in a two dimensional surface. Among them line dynamics is the most important element which uses lines converging into one or more vanishing points to create a linear perspective where the subject appears to get smaller as it recedes into the distance thus conveying a sense of depth in the picture.

Perspective in architectural photography composition
Perspective in architectural photography composition

Traditionally exterior shots are mostly taken from two angles, one is a straight on shot of the front elevation and second a 60°/30° perspective shot comprising of two thirds of the front elevation and one third of the side elevation.

Straight on Front Elevation Shot

A straight on front elevation shot is not often used as the main general view of the building as such a shot will inevitably be two-dimensional in appearance except for any three dimensional texture details on the building's surface. Such as shot finds use more as a photographic extension of the architect’s original front elevation drawing.

60°/30° Perspective of the Front Elevation

A 60°/30° Perspective  shot  concentrates more on the front elevation all the while allowing a more oblique view of the side elevation also to appear in the composition. In such a composition if we divide the entire frame into thirds, two thirds of the composition will be occupied by the front elevation and the remaining one third will be featuring the side elevation. The diminishing perspective shown by such a composition is the main element that creates a sense of depth in the picture.

Controlling Perspective with Focal length

Controlling perspective in architectural photography using focal length
Controlling perspective in architectural photography using focal length

Lenses of different focal length produces different perspectives. Normal lenses conveys a more or less natural perspective (same as the natural perspective of the human eye), lenses wider than normal lenses dramatically enhances perspective and lenses shorter than normal lenses produces a more compressed perspective.

The change in perspective brought about by different focal length lenses is actually the result of changing the shooting distance from the building and using correspondingly longer or shorter focal length lenses to maintain the same amount of subject magnification. The wider the angle of view, the more you can see of the lines that are converging to one or more vanishing points. The narrower the angle of view, the less you can see of these lines.

Put simply to include the same amount of the building with a wide-angle lens as with the standard, you would have to move closer to it. The effect of this is exaggerated perspective that both enhances the dominance of the building and the dynamic structure of the image.

Normal Lens

Normal lenses are used in architectural photography to convey a natural perspective to the viewer. The scene when captured with a normal lens will resemble the view one gets as if he/she is physically present on the scene. No exaggeration or compression it is just the view as a human eye will see it.

Wide Angle Lenses 

Wide angle lenses are the main stay of architectural photographers both for the dynamic perspective they produce and also of their ability to capture whole buildings where space is restricted. One limitation of wide angle lenses is that they could not be used in situations where the roof structure of the building is an important factor to be included in the composition. Being very close to the building the roof structure could not be covered by the lens; shooting from further away using a longer focal length lens is the only alternative.

Tele Photo Lenses

Long focal length lenses flattens the perspective by compressing the space between different elements in the frame. Longer focal length lenses are often used for showing building within the context of its surroundings or for selectively isolating a building from the surrounding structures. However the use of long focal length lenses are often restricted because to capture the subject at the same magnification in the frame as a wide angle lens, the camera has to be moved much further from the subject and this has many practical limitations. Often there is not enough space to back the camera up or there is no suitable vantage point to get a clear un obstructed view of the structure.

Focal Length and Depth of Field

While using lenses of different focal lengths, it should be remembered that depth of field in an image varies with focal length (shooting distance). The shorter the focal length the greater the depth of field and vice versa. So to get the same amount of depth as that of a wide angle lens longer focal length lenses need to be stopped down.  

In the next article we will discuss about perspective in interior shots.

Related Reading

  1. Architectural Photography Composition - Line Dynamics
  2. Composition in Architectural Photography
  3. Tripods for Architectural Photography
  4. Architectural Photography Tips - Necessary extras
  5. Perspective Control A.K.A Tilt Shift Lenses