In this article I will try to explain how perspective works in a 2D photograph with some tips, myths and example photos.
When we see a photograph on computer screen or on prints, we are looking at a 2-dimensional representation of a real 3-dimensional scene. And that is what photography is all about – capturing a 3D scene onto a 2D image. I used to wonder how do photographers demonstrate “depth” or sense of “scale” in a (good) photograph. They use the concept of Perspective.
This is one of the tricky areas of photography which if a photographer is not consciously aware of, can produce unwanted “distortions” or “flat” uninteresting images.
3D is real. A 2D depiction of a 3D scene is just an illusion exploiting how our brain synthesizes information to determine the “depth” in real-time. Powerful compositions can be created by applying the concepts of perspective in effectively converting a 3D scene into a 2D translation.
Let’s start by formally defining “Perspective”
Perspective in photography can be defined as the sense of depth or spatial relationships between objects in the photo, along with their dimensions with respect to the viewpoint (camera lens or the viewer).
Now let’s come down to the techniques –
I. Blocking, overlap or obstruction
This is probably the dumbest thing to tell. But let me tell you anyways. When we see an object blocking the view of another object, the first object is nearer to the viewer than the latter.
This clue to our brain regarding distance can be utilized in a photograph to depict the “depth” or distance between the objects also called overlap perspective. If this overlap is repeated in a same picture the viewer gets a sense of depth among various objects lying in a 3D reality through the perception of the relative distance of objects made by partial blocking and hiding.
II. Relative Size
Our brain is very complex but gets fooled easily. We have a notion that when an object becomes more distant, it appears smaller than the one which is closer to the viewer.
In reality our brain has encodings of “natural” size of different objects like trees, cars, people and animals. So when we see a person twice as big as building, we cannot rationally conclude that the person is actually twice as big in reality. Our brain tells us that the building is farther away for a person. Alternatively when we carefully place different objects at different distances but giving an illusion that they are in the same plane produces funny images.
So in a nutshell, our brain makes an evaluation of the sizes based on “known” objects in relationship with other objects in the photo. Thus a distance is “imagined” in the brain and creates the “depth” in the photo that the photographer is looking for. This is also called “scaling” which helps the viewer to determine the actual size or relative size of the objects in the picture.
III. Linear, Rectilinear and Vanishing Point
As already mentioned earlier that a 2D image is nothing but an illusion of a 3D scene, but nevertheless artists and photographers utilize this illusion effect as an important compositional factor in their works.
The human eye judges distance by the way lines and planes converge at an angle. This is known as linear perspective.
This when expanded to the rectangular objects, you find that some of the lens (fish-eye and panoramic) produces objects at the sides much smaller than it actually is and the objects at the center much larger that it’s actual size. Geometrically all straight horizontal lines at the lens axis level are represented as straight lines, and all other straight horizontal lines either above or below the lens axis level are reproduced as curved lines. But with “rectilinear perspective” the straight lines in the subject are reproduced straight in the picture (normal lenses are rectilinear lenses) which is way we see things normally.
It is noteworthy to mention that any photo is subject to “perspective projection distortion” which can be controlled and corrected with various methods that I will describe in Part II of this series.
The fish-eye and panoramic lenses produces “false” perspectives and are used only to produce “special” effects on purpose (more on this in Part II: Playing with perspective).
So back to linear perspective. Lines that are parallel to each other when seen at a great distance gives us the sensation of meeting (at vanishing points) for example in rail tracks. This “converging parallel lines” illusion can be used to show “distance” or depth in the photo.
IV. Lack of Sharpness, Color Quality or Contrast
We are accustomed to our eyes not able to figure out objects in the distant far off (due to lowering of contrast or scattering of light or both). We can use this information to “create” the effect of lack of sharpness/contrast by controlling the depth of field. Now controlling depth of field is totally different subject area in Photography and I do not want to mix it with the current discussion of perspective control. But just for the sake of completeness, I can give you a quick hint: just focus your lens slightly shorter than infinity so that the farthest object looks blurred thus giving the viewers a sense of distance.
Also atmospheric conditions like haze/fog/dust can cause loss of image sharpness at a distant. Since the effect of this “haze” (scattering of light due to particles in the air) is proportional to the distance of the objects from the lens, we can use this information as well in composing the shot.
Of course, there are various different factors that contribute to varying atmospheric conditions but the result effect of reduction of contrast, brightness and saturation can make our eyes believe that we are looking at something really distant compared to the objects that are clear, sharp and vibrant color.
So next time when you are trying to compose a photo, before pressing the shutter, think again. Are you able to successfully illustrate the “3D-factor” through any (or all) of the above mentioned “illusion” methods. In Part II of this article, I will explain the myth on perspective, zooming/framing and distortion corrections.
About the Author
Sudipta Shaw is a software professional and a self-made photographer. He also likes to teach and mentor.
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