What is the definition of perspective? In its broad visual and optical sense, perspective concerns the methods, processes and systems through which spatial reality is viewed, imaged, projected, measured, represented or otherwise made visually apparent, together with the resulting image, view or spatial appearance.
A concise perspective definition therefore needs to encompass much more than perspective drawing. Perspective may arise naturally through vision and optical processes, or artificially through geometry, drawing, photography, instruments, projection, computer graphics, simulation and digital media. It concerns both how a perspective is produced and what visual or spatial form results.
In the terminology of the Dictionary of Perspective, this fundamental distinction can be expressed simply as:
Perspective = method or process + resulting image, view or spatial appearance.
Definition of Perspective
The word perspective has acquired many meanings. Historically it has been associated with the science of sight and optics, the geometrical construction of images, the appearance of visible objects, a drawing or picture produced according to perspective, a visible view or vista, and more generally a particular point of view.
Within the field of visual, optical and technical perspective, however, these meanings are closely related. They concern relationships between spatial reality, viewpoint, vision, optical or geometrical processes, image formation, projection and representation.
Perspective may consequently describe a method, a process, a system, a visual phenomenon, an image form, or the resulting view or representation. This is one reason why a single narrow definition of perspective can be misleading.
What Does Perspective Mean?
At its most fundamental level, perspective relates to a mode of visual appearance: a particular way in which spatial reality appears as a result of viewpoint, viewing or imaging conditions, projection, optical behaviour, representation and perception.
An object does not necessarily appear visually identical to its known physical geometry. Equal lengths can appear unequal, parallel lines can appear to converge, surfaces change their apparent shape as their orientation changes, distant objects may appear smaller, and colour, contrast, detail and visibility may change with distance and atmospheric conditions. Such changes are among the many phenomena and forms studied within perspective.
Perspective is therefore concerned with the relationship between what exists in spatial reality and how that reality becomes a view, image, measurement, model or representation.
Perspective Is Not Simply Perspective Drawing
One of the most important points in defining perspective is that perspective is not a single drawing method. Linear perspective, one-point perspective, two-point perspective and three-point perspective are important forms of graphical and mathematical perspective, but they occupy only a small part of the total field.
Perspective also occurs in natural vision, optics, photography, cameras, telescopes, microscopes, projection systems, architecture, painting, technical drawing, cinema, computer graphics, scientific imaging, virtual and augmented reality and many other visual technologies.
The Dictionary of Perspective consequently organises perspective into principal categories including Natural Perspective, Visual Perspective, Optical Perspective, Mathematical Perspective, Graphical Perspective, Instrument Perspective, Simulated Perspective and New Media Perspective.
Perspective as Method and Outcome
A major source of confusion in any definition of perspective is that the same term can refer both to the process that produces an appearance and to the appearance that results.
For example, linear perspective can describe a mathematical system of projection, a graphical construction method, an optical or visual appearance involving convergence, or the geometrical form visible in the completed image. Similarly, spherical perspective may describe a method of projection, a curved image geometry, an optical field of view or the resulting spherical representation.
To define perspective accurately, it is therefore often necessary to ask two different questions:
- What perspective process, method or system is operating?
- What perspective appearance, image, view or form does that process produce?
Distinguishing method from outcome provides a much clearer foundation for understanding perspective terminology.
The Two Basic Directions of Perspective
Perspective processes can also be distinguished by the direction in which they operate. The Dictionary of Perspective identifies two principal classes: the Viewing or Imaging Class and the Projecting Class.
In the Viewing or Imaging Class, light, visual information or spatial data passes from an object, scene or existing image towards an eye, sensor, image plane or imaging system, where a view, image, measurement or representation is formed, captured or perceived. Human vision and camera imaging are familiar examples.
In the Projecting Class, light, images, shadows, lines or spatial information are projected forwards from a source or representational system into physical, graphical, optical or simulated space. Projection systems and geometrical projection provide examples.
Some perspective systems employ both directions sequentially. A camera-projector system, for example, can first capture an image and then project or display it.
Perspective Categories, Types and Forms
A comprehensive perspective definition also requires a distinction between a perspective category, type and form.
A perspective category identifies the principal source or mode of a perspective process: how an object, scene, image or view is observed, formed, calculated, constructed, projected, simulated or represented.
A perspective type is a particular method, system, process or subdivision within one or more categories. Examples include linear perspective, aerial perspective, spherical perspective, reverse perspective, stereoscopic perspective, panoramic perspective, anamorphic perspective and forced perspective.
A perspective form is the visual, optical, geometrical or spatial appearance produced by a perspective process. Perspective form can involve changes in apparent size, shape, aspect, position or direction; convergence or divergence; gradients of colour, clarity, contrast or illumination; spatial curvature or distortion; and apparent depth, volume or immersion.
Perspective can therefore be analysed not merely by naming a familiar drawing technique, but by identifying the category, class, type, form, phenomenon, function and product involved.
Natural, Visual and Optical Perspective
Perspective exists before anyone makes a drawing. Natural Perspective concerns perspective arising from the physical organisation and visible appearance of objects and scenes in natural space. Spatial recession, relative size, overlap and atmospheric effects can all contribute to natural appearance.
Visual Perspective concerns visual appearances, views and images. Within this broad category, Visual Perspective Type 2 concerns perspective as formed and experienced through the human visual system, including retinal and perceptual appearance, viewpoint, apparent size and shape, monocular and binocular vision, depth cues and visual acuity.
Optical Perspective concerns perspective formed, transmitted, modified or projected through light or other electromagnetic radiation. It includes direct optical views and images produced through reflection, refraction, focusing, projection and related optical processes.
A normal act of seeing can therefore involve several related perspective processes rather than one isolated type.
Artificial and Represented Perspective
Perspective can also be deliberately calculated, constructed, recorded, modified or represented. Mathematical and graphical perspective use geometrical relationships, measurements and constructions. Instrument perspective includes images and views produced through cameras, lenses, microscopes, telescopes, mirrors, projectors and other devices.
Simulated perspective deliberately alters physical space, objects or images to produce a selected visual effect or illusion. New Media Perspective extends perspective into computer graphics, digital imaging, computer vision, artificial intelligence, virtual reality, augmented reality, mixed reality and interactive three-dimensional environments.
This wider framework demonstrates why defining perspective only as “drawing three-dimensional objects on a flat surface” is inadequate. That describes one important application of perspective, not the field as a whole.
Why Is Perspective Difficult to Define?
Perspective terminology has developed across art, optics, geometry, architecture, photography, science and technology over many centuries. As a result, different terms have sometimes been used for the same concept, while the same term may be used for different concepts.
The word perspective itself may identify a method, process, system, instrument, function, phenomenon, image form, view or outcome. Conversely, a single perspective concept may possess several different names.
Perspective Category Theory was developed to help clarify this problem by separating the different levels and functions involved and by relating perspective categories, classes, types and forms to their methods, processes, goals and outcomes.
Perspective Defined in One Sentence
Perspective is the field concerned with the methods, processes and systems through which spatial reality is viewed, imaged, projected, measured or represented, and with the visual, optical, geometrical or spatial appearances, images and views that result.
This broad definition of perspective accommodates natural vision and optical appearance as well as mathematical projection, perspective drawing, photography, instruments, simulation, computer-generated imagery and other forms of spatial representation.
Perspective Definition: Frequently Asked Questions
What is the definition of perspective?
Perspective concerns both the processes through which spatial reality is viewed, imaged, projected, measured or represented and the resulting visual or spatial appearance. It can therefore refer to a perspective method or system and also to the image, view or form produced by that system.
How do you define perspective?
The broadest useful definition is to treat perspective as a field connecting spatial reality with visual appearance, imaging, projection, measurement and representation. Different perspective categories and types describe the particular processes involved.
Is perspective the same as linear perspective?
No. Linear perspective is one important type of mathematical and graphical perspective, but perspective as a whole includes natural, visual, optical, mathematical, graphical, instrument, simulated and New Media processes, together with a very large number of individual types and forms.
Is perspective only a drawing technique?
No. Perspective drawing is one application of perspective. Perspective also operates through human vision, optical systems, photography, projection, scientific imaging, cinema, computer graphics, simulation and many other technologies and forms of representation.
What is the difference between a perspective method and a perspective form?
A perspective method or process concerns how a particular perspective is produced. A perspective form concerns the visual, optical, geometrical or spatial appearance that results. The same traditional perspective term may sometimes refer to both.
Why are there different definitions of perspective?
Perspective has developed across many different disciplines and has historically referred to sight, optics, geometry, drawing, visual appearance, images, views and points of view. Modern perspective additionally encompasses photography, scientific imaging, computer graphics, digital media and immersive technologies. A comprehensive definition therefore needs to distinguish these different but related meanings.
A Wider Understanding of Perspective
Perspective is ultimately much larger than any one artistic technique or geometrical construction. It provides ways of viewing, imaging, measuring, matching and representing spatial reality, as well as creating visual illusion and immersive experience.
Understanding perspective therefore requires us to consider the complete relationship between spatial reality, viewpoint, optical and geometrical processes, visual appearance, perception, image formation, projection and representation. Seen in this wider sense, perspective forms a common visual field connecting art, science and technology.