The Optical Image Chain is the series of objects, devices, images, spaces and processes involved in the formation, capture, processing, display, analysis, storage or transmission of a perspective image or view.
It provides a systematic way of tracing the journey of visual or spatial information from an original Object or Target Space through one or more imaging stages to a resulting Image or Perspective Space.
The principal elements of the Optical Image Chain are:
Object → Imager → Sensor → Image → Processor → Display → Analysis → Storage / Transmission
The concept is especially useful for understanding complex perspective systems in which an apparently simple final image is actually the result of several successive optical, instrument, digital and visual processes.
The Optical Image Chain within Perspective Category Theory
Within Perspective Category Theory (PCT), the Optical Image Chain provides a practical structure for identifying how Perspective Categories, Classes, Methods, Processes and Spaces interact in the production and viewing of an image.
A complete chain may involve:
- a Perspective Object / Scene;
- an original Object or Target Space;
- one or more Perspective Categories;
- one or more imaging or projection processes;
- intermediate images and spaces;
- a resulting Perspective Image / View;
- a final or intermediate Image Space; and
- subsequent human or technical interpretation.
The Optical Image Chain therefore helps reveal how a Perspective Product has actually been produced, rather than treating the final image as an isolated object.
The Eight Principal Elements
The Dictionary of Perspective identifies eight principal elements of the Optical Image Chain:
- Object — the object being imaged in Object Space;
- Imager — the device or system that images, or purports to image, the object;
- Sensor — the component that converts incident optical energy into a signal from which an image is formed;
- Image — the resulting Perspective Image in Image Space;
- Processor — a system that processes the image data;
- Display — a system that presents the image;
- Analysis — the process of analysing the image;
- Storage / Transmission — the storage or communication of the image or associated data.
These elements form a general analytical framework rather than merely describing one particular camera or optical instrument.
1. Object
The first element is the Object: the spatial object, scene or information towards which the imaging system is directed.
The object exists within Object Space.
It may be:
- physical;
- artificial;
- simulated;
- represented; or
- imagined.
The object or scene provides the spatial source from which the subsequent Perspective Image or View is derived.
In a broader system, the relevant target may consist of a complete spatial scene rather than one isolated object.
2. Imager
The Imager is the device or system that forms or captures an image of the target.
Examples identified in Volume 1 include:
- the human eye;
- a camera;
- a telescope; and
- other optical imaging systems.
The Imager establishes an optical or technical relationship between the Object Space and the emerging Image Space.
Different imagers may produce substantially different images of the same target because they can employ different optics, apertures, fields of view, sensors and image geometries.
3. Sensor
The Sensor receives the optical energy delivered by the imaging system and converts it into a form from which an image can be formed or recorded.
In digital imaging, this commonly involves converting incident optical energy into an electrical or digital signal.
Volume 1 notes that the Sensor may sometimes be considered as part of the broader Imager.
Nevertheless, separating the two analytically is useful:
Imager → forms or directs the optical image
Sensor → detects or records the delivered information
This distinction becomes particularly important when comparing biological vision, photography and scientific imaging systems.
4. Image
The Image is the Perspective Image produced within Image Space.
It is a transformed representation of the original target rather than necessarily a complete reproduction of Object Space.
A three-dimensional scene, for example, may become a two-dimensional photographic or digital image.
During this transformation, some spatial information may be preserved while other information may be reduced, concealed, distorted or lost.
The Image therefore forms an important intermediate or final Perspective Product within the chain.
5. Processor
The Processor acts upon the image data after or during image formation.
Processing may alter or organise information relating to:
- image geometry;
- scale;
- resolution;
- brightness;
- contrast;
- colour;
- clarity;
- orientation; or
- other image characteristics.
Processing therefore constitutes another possible Perspective Transformation within the complete image chain.
In modern digital systems, several processing stages may occur before the image reaches its final displayed form.
6. Display
The Display presents the image for viewing, projection or further use.
A display may introduce a new Image or Perspective Space that differs from the preceding captured or processed image.
Examples can include:
- a photographic print;
- a cinema screen;
- a television;
- a computer monitor;
- a digital projection surface; or
- another visual display system.
Display should therefore not always be regarded as a neutral final stage. The geometry, scale, resolution and physical form of the display may contribute to the final appearance of the image.
7. Analysis
Analysis concerns the interpretation or measurement of the resulting image and the information it contains.
This may be undertaken by:
- a human observer;
- a scientific or technical specialist;
- a measurement system;
- a computer-vision system; or
- another analytical process.
The image may therefore be used to derive information concerning such properties as Form, size, position, orientation, spatial arrangement or activity.
Analysis may itself involve further processing rather than simply passive viewing.
8. Storage and Transmission
The final principal element is Storage / Transmission.
An image or its associated data may be:
- stored;
- copied;
- transmitted;
- broadcast;
- archived; or
- passed into another imaging or display system.
Storage and transmission are important because a Perspective Image does not necessarily terminate when it is initially formed.
It may subsequently enter another Optical Image Chain and become the target of further processing, projection, display or viewing.
Target Space
Target Space is the original Object Space towards which the perspective system as a whole is directed.
It contains the spatial object, scene or information that the resulting images directly or indirectly represent.
Thus:
Target Space → Optical Image Chain → Final Image Space
The concept is important because an image chain may contain several intermediate images and spaces while still referring ultimately to one original target.
A photograph, television image or processed digital image may all remain representations of the same original physical Target Space.
Object Space and Image Space
The Optical Image Chain connects two fundamental spatial concepts:
Object Space — the space containing the original object or scene;
Image Space — the space containing the resulting Perspective Image or representation.
The relationship can be expressed as:
Object Space → imaging and transformation processes → Image Space
The two spaces should not be confused. A three-dimensional physical Object Space may, for example, be transformed into a two-dimensional photographic Image Space.
That image can be geometrically valid according to the selected imaging model while still preserving only part of the spatial information present in the original scene.
Intermediate Images and Spaces
Complex Optical Image Chains may contain one or more Intermediate Images or Intermediate Spaces.
The Dictionary defines an Intermediate Perspective as a projection existing between Target Space and the final Image Space.
For example:
3-D Physical Target Space → Camera Image Space → Processed Digital Space → Display Space → Retinal Image Space
Each stage is a representation or transformation of information received from an earlier stage.
These intermediate spaces are therefore important waypoints in understanding how the final image or visual experience has been produced.
Intermediate Spatial Reality
The Dictionary uses the related term Intermediate Spatial Reality for an intermediate representation occurring within the Optical Image Chain.
A camera, for example, may produce a two-dimensional Instrument or Image Space representing an original three-dimensional Target Space.
Lenses, sensors, processing and display may then introduce further:
- transformations;
- distortions;
- information loss;
- changes of scale;
- changes of resolution; or
- other Perspective Phenomena.
When a human subsequently views the image, another optical image is formed on the retinas, adding a further stage to the chain.
The Optical Image Chain in Human Vision
Direct human viewing provides a relatively simple example.
The Target Space is the natural or physical environment being viewed.
The human visual system then forms optical images on the retinas.
In simplified form:
Physical Object / Scene → Eye → Retinal Image → Visual Interpretation
The physical environment and the retinal or visual image occupy different spatial roles.
The first is the Target or Object Space; the second forms part of the resulting visual Image Space.
The Optical Image Chain in Photography
Photography introduces an Instrument Perspective stage between the original scene and the resulting image.
A simplified photographic chain is:
Physical Scene → Camera Optics → Sensor → Photographic Image → Processing → Display
If a person then looks at the displayed photograph, the chain continues:
Display → Eye → Retinal Image → Visual Interpretation
The original three-dimensional physical Target Space therefore remains distinct from the two-dimensional photographic Image Space and the later retinal or visual Image Space.
The Optical Image Chain in Cinema
Cinema provides a more complex example because image formation and image projection both participate.
A simplified chain may be represented as:
Scene → Camera → Recorded Image → Processing → Projection / Display → Screen → Viewer → Retinal Image
The system therefore contains both fundamental Perspective Classes:
- Viewing or Imaging during image formation or capture; and
- Projecting during presentation of the recorded image.
The complete cinema system may consequently involve Mixed Perspective as well as several interacting Perspective Categories.
Digital Optical Image Chains
Digital imaging can introduce several additional processing and representational stages.
For example:
Physical Scene → Optical Imaging → Digital Sensor → Digital Image → Processing → Storage / Transmission → Display → Human Viewing
Digital Perspective can therefore be created from or projected from physical, instrument, mathematical, graphical, imaginary or other spatial realities.
The resulting Digital Image Space may then become an intermediate stage before another display, projection or visual process takes place.
The Chain can contain several Perspective Categories
An Optical Image Chain frequently passes through more than one Perspective Category.
For example:
Natural → Optical → Instrument → New Media → Visual Perspective Type 2
This is an example of Category Chaining.
The final viewed image may therefore be shaped by several Perspective Categories rather than belonging exclusively to one.
The Optical Image Chain provides the practical structure within which these successive categories can be identified.
The Chain can contain both Perspective Classes
The Optical Image Chain can also be analysed according to Perspective Class.
The two basic directional classes are:
- Viewing or Imaging — image formation or capture; and
- Projecting — projection of light, images or spatial information forwards.
A camera followed by a projector provides a simple example:
Viewing or Imaging → Projecting
The Optical Image Chain can therefore reveal not only which Perspective Categories operate, but also the directions in which different stages of the overall system function.
Optical Image Chain and Category Chaining
Optical Image Chain and Category Chaining are closely related but are not synonymous.
The Optical Image Chain identifies the sequence of objects, devices, images and processes through which image information passes.
Category Chaining identifies the sequence of Perspective Categories operating within that process.
Thus:
Optical Image Chain → physical and operational sequence
Category Chaining → categorical sequence
Both forms of analysis can be applied to the same perspective system.
Optical Image Chain and Composite Perspective
A Perspective Image produced through several categories or processes may constitute Composite Perspective.
The Optical Image Chain allows those contributing stages to be identified individually.
For example, a digital photograph viewed on a screen may involve:
- Natural Perspective;
- Optical Perspective;
- Instrument Perspective;
- New Media Perspective; and
- Visual Perspective Type 2.
The image may appear singular to the final observer while actually being the result of a complex multi-stage perspective system.
Perspective Transformations within the Chain
Each stage of an Optical Image Chain may introduce a Perspective Transformation.
These transformations may affect:
- geometry;
- size;
- shape;
- scale;
- position;
- orientation;
- resolution;
- colour;
- contrast;
- clarity; or
- depth information.
Volume 1 therefore argues that understanding how a Perspective Image has been formed requires identifying and modelling the intermediate Perspective Transformations and Phenomena involved.
Information can be lost or altered
The Optical Image Chain is not necessarily a perfect transfer of spatial information.
For example, a camera may map a three-dimensional Target Space into a two-dimensional Image Space.
The projection can be geometrically valid according to the selected camera model while still:
- losing depth information;
- including optical distortion;
- reducing detail;
- altering scale relationships; or
- introducing other Perspective Effects.
Further processing, compression, display and viewing stages may introduce additional transformations.
The final image should therefore not automatically be treated as an exact duplicate of the original Object Space.
One Image Space can become another Target Space
An important feature of a chained perspective system is that the Image Space produced by one stage can become the target of another.
For example:
Physical Scene → Photograph → Digital Scan → Processed Image → Display → Human Vision
The photograph is initially the Image-Space Product of the camera.
When it is scanned, processed or photographed again, it becomes the target of a further Perspective Process.
Thus:
one system’s Image Space may become another system’s Object or Target Space.
This explains how long sequences of related Perspective Images and Spaces can develop within one complete imaging process.
The final image is not always the end of the chain
A Perspective Image that appears to be a final Product may subsequently become an intermediate stage in another system.
It may be:
- copied;
- photographed;
- scanned;
- processed;
- projected;
- transmitted;
- analysed;
- displayed; or
- viewed again.
The Optical Image Chain is therefore potentially extensible rather than necessarily terminating with the first image produced.
Why the Optical Image Chain matters
The Optical Image Chain provides a means of identifying, registering and mapping the journey of an image from Object Space to Image Space.
It helps distinguish:
- the original object from its image;
- Object Space from Image Space;
- the Imager from the Sensor;
- image formation from subsequent processing;
- captured images from displayed or projected images;
- intermediate representations from the original Target Space;
- one Perspective Category from the next;
- Viewing or Imaging processes from Projecting processes;
- the initial Perspective Product from later transformations of that Product; and
- the final visual appearance from the complete sequence of processes that produced it.
The Optical Image Chain is therefore the complete sequence of objects, imaging systems, sensors, images, processors, displays, analytical processes and storage or transmission stages through which perspective information may pass from an original Object or Target Space towards one or more resulting Image Spaces.
Related Perspective Topics
Object Space →
Image Space →
Perspective Process →
Perspective Product →
Perspective Image / View →
Perspective Transformation →