Film and digital technologies are often treated as interchangeable terms when discussing photography because both can produce an image, but are these technologies indeed interchangeable?
Every medium is distinguished by a unique set of properties which in turn affects the meaning of work produced within that medium. Digital cameras are built to mimic the function and ergonomics of film cameras and so it is useful to examine the nature of film technologies when attempting to understand the current state of digital camera and sensor technology.
When using a film camera, light reflects off objects and passes through the lens where it is focused onto a piece of film. Colour film is made up of layers of light-sensitive material called emulsions, each of which are sensitive to different wavelengths of light, most often that of red, green and blue. Each layer of colour emulsion is actually monochromatic and when all layers are overlaid a colour image can be formed. These layers typically contain silver halide crystals (grains) and colour dye couplers in a base of gelatin. Silver halide crystals are naturally sensitive to light and once exposed a chemical reaction occurs that alters each crystal, invisibly allowing a latent image to be formed by the altered crystals in the emulsion. The film is then developed in chemicals which cause the affected silver halide crystals to react and interact with the colour couplers producing clouds of coloured dye in those areas. More chemicals are then used to remove the silver halide crystals leaving only the dye.1
Film photography operates in a purely physical space and is purely objective in its record of the forms and values of the light projected onto it. The visible final image of the developed film exists as a linear physical trace of the light that was projected onto it, a record of the light that was reflected from the original scene and the interaction of this light with the film. The image on the film thus contains similarly positioned and proportioned forms and values to the light that was projected on it.
It is similar to if one were to throw a rock against a fence leaving scrape marks on that fence. Such marks become an index of that rock. The fence after such an event continues to persist with these marks, preserving the evidence of its interaction with the rock. The marks describe the rock and act as a pointer to the rock. Photography works in the same way. Translated from the Greek root words, photo means “light” and graph means “draw”. At the level of semantics, the term photography implies a visible physical record (drawing/ writing) through an affection by light. A photograph is a persisting artifact of a physical interaction between light and a light-sensitive medium.
The image on developed film is an original. Prints can be made from film by projecting light through the film onto light-sensitive paper, but the film itself cannot be duplicated exactly. Such prints are themselves new photographs of existing photographs (the film). Likewise, exposing photographic paper with lasers using LightJet, Chromira, Fuji Frontier, etc, printers produces new photographs, photographs of lasers. Inkjet printers in contrast are in essence a form of painting.
It is at the fundamental level of function, the recording of light, that digital camera sensors diverge from film. Digital camera sensors utilize analog elements at their core. There are various configurations of these sensors currently in use. Most consumer digital cameras use either the charge-coupled device (CCD) or the active-pixel sensor (APS or CMOS). Both of these sensor designs function in similar ways. Each uses an array of microscopic photodiodes which are capable of independently generating electrical currents linearly proportional to the intensity of light they are exposed to. The electrical currents produced are sequentially fed through an analog-digital converter which yields digital values that are then stored in a digital memory. Since each photodiode is capable of measuring luminosity only, solid coloured filters (red, blue and green) are positioned over each photodiode in an alternating checkered pattern called a Bayer filter mosaic. Each photodiode is covered by a single colour and measures the value for that colour alone. The digital values collected from these photodiodes are then interpolated by software involving complex algorithms. A list of colour values is calculated by this software, combining the red, blue and green values into a fuller chromatic spectrum. The raw digital data cannot form an image without interpretation as it is simply a list of electrical current measurements.
Where film generates a physical record, the electrical measurements of light created in a digital sensor are temporary. The resulting image information is not a trace to some original light as it is with film but is a measurement turned statistic. The colour statistics produced are arbitrary and abstract in their signification of the values originally measured.
There is nothing inherent to the digital image file that makes it an image. Digital image files contain sets of binary-based numeric values acting as a code which requires a key for translation into an image. While digital image files are typically produced with the intention of using specific software to interpret the data, the symbolic nature of the values in these files does not predestine their interpretation to any one software program, leaving interpretation completely open. Different software programs can interpret the data differently, such as text or hex editors which will not interpret the data into an image that resembles the light originally projected onto the sensor. The data can easily be interpreted into other mediums like sound instead of light. Even different programs intended to display images often interpret these colour values differently. Monitors and printers also vary greatly in how they display these interpreted colour values.
The digital image is not inherently visual; it is abstract and has no visual or physical form. The digital image is not fixed and finds its base description in language rather than physical value. There is no original in digital imaging and every copy is identical (one might also argue that there are a theoretical infinite number of identical originals, if the notion of the original is not associated with the physical object and is applied to the idea or symbol).
The digital image operates in a purely symbolic space and is purely subjective, a significant contrast to the film image’s purely physical and objective nature. As a set of data, the digital image has no direct connection to the scene that was photographed; its relationship to that scene is obliterated by the symbolic basis and origin of that data, data which has also been affected by screens of constructed data and second and third-hand representations (and manipulations) of that data. Digital images are a type of computer rendering similar to motion capture and computerized roto-scoping where measurements are made from objects and then visually rendered in virtual as a simulation.
In film photography, decisions that impact the way light will affect interaction with a medium are made before the exposure when the film chemistry or photographic paper is produced and selected. Once a photograph is produced, it is fixed. Any manipulation or change enacted after the production of the photograph, such as physical manipulation or environmental factors, are effects on the original photograph and do not produce a new photograph.
With digital imaging, a photodiode is a generic translator of light and any decisions must be made post-exposure either in the camera’s software or a user’s software. Commonly there are of course Bayer, ultra-violet and anti-alias filters that may have been placed over the sensor or filters placed over the lens, however these filters are effects and not affects; filters do not affect or change the way light interacts with a medium (and in the case of the digital sensor there is no medium to affect), rather filters change the light itself before any potential interaction can occur.
Given that digital image data is completely subjective in nature it lacks authenticity as it has no finalized form—its essence is effect-based. This is in direct contrast to film’s affect-based nature. A digital image edited with a software program like Photoshop is no more or less authentic than the image data delivered from the digital camera or any other kind of image data. All digital images are purely orphaned data, meaningless simulacra that lack an inherent object or form to dictate existence. Digital images can only be seen as images through other media, like an LCD display or a printer.
Film photography produces a still image because of a limit in the material media of film itself. As film is exposed, the reaction to light causes a change in value. There is a material limitation to the amount of exposure film can endure before this reaction fades and ceases, the change in value having reached a maximum. After a certain amount of exposure the film becomes uniformly exposed and thus devoid of detail (in which case it remains a record of light, just one without a visible differentiation of detail). Film produces an image most similar to the way a person might have perceived the light shone on it when a balanced reaction in the film is enacted, a midpoint between a reaction of nothing and everything.
Here also digital image capture differs from film as the effect that occurs when the photodiodes are exposed to light results in the production of a constant and perpetual electrical current. Digital sensors are typically configured to store this current in an additive fashion, and this storage occurs after and apart from the translation of light to energy by the photodiode. While the silver halide grain reacts to light for only a limited duration before a maximum saturation of affect is reached, the photodiode is capable of converting light to current indefinitely. In a sense it is not a “light-drawing” but a “light-measurement” as no drawing or interaction is made, only a measurement and then release of light-energy. The light does not interact with the sensor but is preserved as energy, energy which is transferred to electrical current by the photodiode. There is no reaction or transformation, only a direct translation to electricity which is then measured before the energy of the light is purged and released from the sensor. Where the film photograph exists as an object, the digital image is virtual and a simulacrum.
A constant value can be produced by a photodiode in place of film’s forced dynamic value. There is no physical limitation for the photodiode's conversion of light energy to electrical current. Light hitting the photodiode could potentially be measured indefinitely even as it changes, resulting in a ceaselessly dynamic stream of light information. Streaming light measurement, a potential underlying nature of digital image capture, calls into further question the relationship of digital image capture to photography and would appear to suggest that it is potentially something else, something which to my knowledge is not precisely defined at present. The potential capabilities of digital image capture are similar to video but present a new form, a seamless and fluid flow of information without inherent visual form and without frames in an undelineated and indefinite measurement. It is a medium of statelessness and statistics. The sensor for digital image capture can be programmed and physically configured to produce still images, but this act truncates the potential of this technology by isolating a fragment of a larger body of potential statistics.
Photography is a narrow field defined by a medium which has interacted with light and remained altered (an imprinted embodiment of that interaction). Digital cameras simulate the results of photography but generate image information only and not physical photographic information. Digital sensors measure light and are not affected or altered in any way by light. The mimicry of film technologies by digital cameras is detrimental both to the progression of digital technologies and to the practice of photography in which film and other photographic technologies are at risk of becoming displaced and lost in favour of a technology incapable of performing the same function, a technology ultimately destined for other largely unexplored functions. Such unexplored functions are very interesting and it should in no way be taken as a negative that digital cameras are not a photography but rather something new.
The physicality of the photograph is an essential part of its message, not just the representation one might see (perceive) in a photograph. The photograph is the message. The digital image however must find forced refuge in shape-shifting, distorted indexes and virtual representations if it is to be perceived, having no object at its core. One is therefore tempted to ask, what is its message?
1 “How Film Makes Images.” Kodak. 16 Aug. 2010
The preceding essay is a revised excerpt from my MFA thesis supporting paper which was submitted in September, 2010. Posted 11/01/2010 and revised 11/01/2010.