Light sensitive material: an introduction

Why do heliotropes move together with the sun, selenotropes with the moon, moving around to the extent of their ability with the luminaries of the cosmos? All things pray according to their own order and sing hymns, either intellectually or rationally or naturally or sensibly, to heads 10 of entire chains. And since the heliotrope is also moved towards that to which it readily opens, if anyone hears it striking the air as it moves about, he perceives in the sound that it offers to the king of the hymn that a plant can sing.

Proclus, On the Priestly Art According to the Greeks.

Picture an enormous flat-bed machine, mounted on rollers and the length of several buildings, dwelling in a narrow pitch-black cavern into which no light can enter.¹ On this machine lies a long strip of paper or film and here it is coated with photosensitive emulsion and dried. Conceive of it as a giant creature, incubated in this cavern. It is a temperamental and hyper-sensitive being, affected not only by light but by temperature, humidity, air velocity, dust, contaminants in the air and in liquid. It is receptive and responsive to human touch and to certain metals. No people are allowed in its cave; it is watched over only by infrared cameras, and other sensors. Picture further, in a different room, lit by electric lights, a man who monitors this creature in its cave, via the images that illuminate several computer screens. Somewhere else in this building there is a group of people who receive and analyse various samples and scans which are extracted and produced by the machines in the darkened chamber.

We are in the factory of Harman Technology, in Mobberley, a village in North-West England. This is one of the factories that belonged to Ilford Limited, the manufacturer which dominated British photographic production in the first half of the twentieth century alongside Kodak Limited (the British branch of the American giant Eastman Kodak). Harman Technology continues to produce Ilford photographic film and darkroom materials here. The factory visit was made as part of an Arts and Humanities Research Fellowship, which also funded archival research on Ilford Ltd, and supported the two-day conference Light | Sensitive | Material, held in London in late 2019.²

The articles in this special issue of photographies journal began life at this conference, which brought together reflections on the material-industrial infrastructure of photography and film manufacture and production with theoretical and philosophical questions about the photographic. The conference encompassed a wide range of topics. It included discussions of atmospheric images, of quasi-photographic or hybrid technologies of light, meditations on the spectral and mnemonic qualities of the photographic or filmic image, and papers that directly addressed the question of the relation between philosophy and photography. The selection of articles included here share a willingness to go beyond the discussion of photographs as representations or figurations, to consider the limits of photographic legibility, the relationship of photographic technologies to other technologies of light and to the photographic capacities of plants. They work with a notion of the photographic which extends beyond distinctions between analogue and digital, or the technical and the aesthetic, and which predates the arrival of photography in its technological form.

As the conference organisers, we wanted to immerse ourselves in the materiality of photography while exploring what Eduardo Cadava describes as the “secret rapport between photography and philosophy”. Cadava claims that this rapport derives from their shared heliotropism: “Both take their life from light”.³ The “heliotropic” aspect of both philosophy and photography refers to their continual turning (tropism) towards the sun, whether as divine light, the light of reason or the sensible object.⁴

In the factory, the dark chamber is where light sensitivity or light receptivity is enabled. The conditions of darkness bring forth light receptivity, but they can only do so through controlled conditions and practices of purification. The dark chamber-cave is also a recurring trope in the history of Western thought, from the subterranean chamber in Plato’s allegory of the cave to the incubation den where patients, under the supervision of the priest, would lie down waiting for Apollo or his son Asclepius to appear in their dreams and cure their ailments. The Pre-Socratic philosopher Parmenides also practiced incubation, lying in complete stillness (hêsychia) in a suspended state between awakening and sleep, to receive divine wisdom and healing power in the darkness of the cave.⁵ To prepare for the visit from the gods, a purification ritual would often take place which would include fasting, praying, bathing, and sacrifice.

The purification rituals of photographic materials continue beyond the factory, in their storage before sale, in their handling by the photographer, and during processing. At every stage, what is being managed is not only exposure to light but other kinds of exposure too. Photographs from the nineteenth century show women factory workers carrying safety lamps to aid their work in the darkrooms. By the 1920s, the photographic factory and the processing labs became even darker, when new panchromatic emulsions made it impossible to use the old safety lights. In addition to keeping out the light, the factory had to be designed so as to exclude other contaminants, particularly in the air. Ilford Limited first began to sanitize their factory environment in 1899, after sulphurous emissions from the nearby Ilford Gas Company fogged 25,000 coated glass plates at Ilford’s London factory in just one day. The company responded by beginning to construct a factory at Brentwood, further away from the London pollution, but also by inventing a system to purify the air inside the factory, essentially an early form of air-conditioning.⁶

In photographic materials production, such control of the environment is to do not just with the materials’ sensitivities but also their instability. Photographic materials can be volatile and even explosive, necessarily so in the case of artificial lighting, such as the pyrotechnic Bengal light discussed in this issue by Niharika Dinkar. As Dinkar explains, Bengal light was a product of colonial exploitation used in military signalling and firework spectacles and its principle ingredient, saltpeter, was also used in gunpowder. Other more inadvertently explosive materials include collodion and celluloid, both central to the history of photographic technologies, and both derived from gun cotton, which combines cotton (a source of cellulose) with nitric acid. Gun cotton was a highly combustible and volatile explosive which was extremely difficult to manufacture and store safely, and celluloid (nitrate based) film notoriously retained gun cotton’s reactivity and flammability.⁷

This material instability is echoed in the conceptual instability of photography: both in writing about photography and in our encounters with photographs, the photographic tends to disappear — “[w]hatever it grants to vision and whatever its manner, a photograph is always invisible: it is not it that we see” — thanks to this self-effacing nature.⁸ Photography is generous, “its hospitality is such that its boundaries are porous and mutable, inviting the encroachment of others”.⁹ These encroachments are theoretical but also material. It is a hospitality that extends to almost everything it touches. As Liz Watkins’ article in this special issue explains, the photographs which are commonly seen as “failed” through overexposure, cracking of the glass negatives, condensation and humidity, extreme temperatures, scratches and fingerprints, can also be viewed as records. She discusses how the “spots, fading, blurring, fogs, specks, and haloes”, the “indecipherable” and the “erroneous” can be read as evidence of historical camera technologies and practices and also a record of the extreme environment and difficult labour of making photographs during early twentieth-century polar expeditions.

Light sensitive materials are first of all sensitive materials, fragile in their substrates (celluloid and acetate, paper and glass) and volatile in their chemistry. There is a tendency to think of these disruptions to the photographic surface or the photographic image as revealing the materiality of photography, but they can instead be seen as revealing its receptivity to impressions, its capacity for recording. Above all, photography records or writes the action of light (it is photo-graphic) but, we want to suggest here, it is also “phototropic”, meaning that it turns towards the light. The term “heliotropic”, usually used to describe a plant such as a sunflower (tournesol) that turns toward the sun, was coined around 1800, the connected term “phototropism” about a century later. If the “-graphy” in photography and the earlier term “heliography”, refers to the way light produces an inscription, tropism reverses the agency. As Richard Shiff writes, “to trope is to turn, often with willful determination”.¹⁰ It offers one way of describing how photography is not just receptive or open to light but actively moves towards it; it does not simply receive an imprint from the light, but seeks it out. This seeking out of light included the photographically-driven expansion of artificial lighting techniques, which enabled an image to be produced even in the darkness of the night, of caves and subterranean chambers, or of northern winters. As Dinkar suggests, this was a commodification of light inseparable from colonial and imperial relations.

The photographic seeking out of light harnessed new technologies but also produced new standards. Its purposeful turning toward the light was embodied in dials and meters, scales and calibrations, the increasingly precise timing of the shutter that facilitated “calculated exposure”.¹¹ Careful control of the amount of light admitted through a lens, as well as the proper production and care of photographic materials, depends on calculations, measurements and rituals devoted to preventing over- and under-exposure, fogging and contamination (unexpected guests taking advantage of photography’s hospitality) but also intended to produce a specific kind of impression or image.

Fig. 1. Sensitometric testing at Ilford Ltd. 1938. Courtesy Redbridge Library and Heritage Centre

Tomáš Dvořák and Jussi Parikka’s article in this issue points to the role of photography in practices of standardisation, and also discusses the standardisation of photography, arguing that measurements do not simply describe pre-existing proportions, but are world-producing. In the photographic factory, photosensitivity is measured and standardised. Photographs from 1938 show young women in Ilford’s Brentwood factory conducting sensitometric testing on batches of Selo film (Figure 1). Measurement systems for the sensitivity of photographic materials were pioneered in the 1880s, although international standards were not aligned until a century later (in the form of ISO — the acronym refers to the International Organisation for Standardization). If the quantifiable photosensitivity of film makes it seem more mechanistic and less like an organism (the creature in the cave), it is worth noting that plant photochemistry, too, is subject to measurement and the application of standards. At the conference, Abelardo Gil-Fournier discussed the Austrian plant physiologist Julius Wiesner, who, in the early 1900s placed plants inside camera obscura-like chambers and measured their photosensitivity. Like films with different ISOs or different types of emulsion (orthochromatic, panchromatic and so on) each species differed. Quantification does not preclude an approach which thinks of plants as sentient: as Gil-Fournier pointed out, Wiesner thought of this in terms of the different dispositions of species, a different enjoyment, jouissance or satisfaction of light, what which he called Lichtgenuss on the part of the plant. Lichtgenuss becomes the standard of measurement.¹²

The photographic precedes its actualization in specific technologies and practices of photography, which could be understood as ways of organising and cultivating its phototropism, its seeking-out of light. This in turn depends on the disposition towards light of the photographic materials. In a discussion of the concept of invention, Derrida remarks that photography sits “in the internal edge of a division” between invention as discovery of that which is already there and invention in terms of new technical production. He asks,

[I]s photography simply the recording of the other or of the object as he or it is there, presented to intuition, independently of the photographic apparatus? Or, on the contrary, does it invent not in the sense of the discovery, the revelation of what is there, but in the sense of technical production?¹³

If photography is an active turning towards the light, then one can see it at work within discourses of mysticism, magic and spiritual practices and at the roots of Western metaphysics.¹⁴ The Syrian Neoplatonist philosopher Iamblichus (ca. 245 C.E.- ca. 325 C.E) coined the term photagogia, which can be translated as “evoking the light” to describe various light capturing strategies in theurgic practices. In his treatise De Mysteriis, written between 280 and 305 CE, Iamblichus tells us that photagogia “illuminates the aether-like and luminous vehicle surrounding the soul with divine light, from which vehicle the divine appearances, set in motion by the gods’ will, take possession of the imaginative power in us”.¹⁵ During theurgic ritual, under the illumination of the gods (which is also a sign of their epiphanies), the theurgist is transformed into light sensitive material absorbing divine light. In Iamblichus’ description above of anagogē or the ascent of the soul, the theurgist’s imaginative faculties (phantaskitē dunamis) are fired up by divine light.¹⁶

In mysticism, the reception of divine light has often been understood as something which has to be worked at through a set of procedures or trained practices. In her keynote at the conference, Laura U. Marks mentioned how, historically, people who we would now call magicians made themselves into “antennae” to capture cosmic energy.¹⁷ In a similar vein, the theurgist needs to prepare himself to be ‘fit’ (epitēdeiotēs) through a combination of virtuous living and theurgic activities for divine reception.¹⁸ In order for divine union to take place, the theurgist needs to transform himself into a receptacle of light. Before the theurgist’s soul container can draw down light, purification of mind and body is required. This involves fasting, praying, and withdrawing into solitude. Illumination comes from the exterior, through the manifestations of the gods. The higher the position of the gods, the stronger the intensity of light emitted. Iamblichus explains the differentials in light intensities, “[T]he greatest light has a sacred brightness which, either shining from above in the aether, or from the air, or moon or sun, or any other heavenly sphere, appears apart from all these things to be such a mode of divination that is autonomous, primordial, and worthy of the gods”.¹⁹

As the luminous vehicle of his soul (ochēma) is lit up by the arrival of various deities, the theurgist endures atmospheric changes such as suffocating heat, earthquake, blinding light as well as bursts of light. Throughout De Mysteriis, one sees a tension between the continual exposure of light and flashes of light. The drawing down of different intensities of light finds resonance in Howard Caygill’s discussion (in this special issue) of Harold Wager’s microscopic photography of plants. What humans perceive as images captured by the plant’s own photographic lenses are in fact the plant’s ability to photograph “differentials in energy”. In his article, the object of the botanist’s investigation becomes the photographing subject, contrary to the giant sequoia in Elizabeth Howie’s article (also in this issue) that resists being photographed.

What Wager’s plant images reveal is the activity of vision stripped bare. As Caygill notes, “In terms of the Copernican Revolution, plants do not resemble humans but humans resemble plants […]. What is perhaps most interesting in all of this is how Wager assembles light, vision and memory in the space of photography”. In addition, photography is doing something strange here, it is photographing plants photographing, thus photographing its own condition of being.

In Joel McKim’s discussion of early computer art in the 1950s and ’60s, we can see something similar in terms of photography’s agency, its ability to produce its object: Ben F. Laposky’s photographs of the transient images on the oscilloscope screen might be read as documentations of his experiments with the oscilloscope (his “Oscillons”) or as the Oscillons themselves, which only come into existence through being photographed. For McKim, this suggests the radical hybrid nature of early computer art more widely. It is tempting to see the photograph as freezing and capturing the mobile light of the oscilloscope, but McKim reads the Oscillons in the context of recent ideas of the photographic image (both digital and chemical) as itself unfixed, durational and dynamic. We might also see them in terms of the peculiarity of photography’s double movement “towards that to which it readily opens” (mentioned in our epigraph). Tropism refers also to figuration, as both Derrida and Shiff discuss, and like the sunflower (the quintessential heliotrope) the photograph resembles that to which it turns, but it also figures it, rendering the moving light of the oscilloscope as an abstract image.²⁰

The question of how photography figures is raised in a different way in Howie’s article where she asks how one might figure the gigantic tree, photographically, and under conditions of “plant-blindness”? Howie’s article addresses both the question of how, practically, such a tree might be photographed (when it cannot be apprehended in its entirety by a human observer) but also what such an image of a tree might signify, how it might figure. What happens when the object being figured cannot be seen either literally or figuratively by human eyes? We might draw a parallel with the stereoscopic image of active volcanoes, taken by the Portuguese naturalist Francisco Afonso Chaves (1857–1926) and discussed at the conference by Victor dos Reis, who argued that these images produce a paradoxical and uncertain perceptive experience, with the camera no more capable of discerning the object of perception than the naked eye.²¹ These difficulties in seeing earthly objects (whether due to a certain “blindness”, the obscuring of the visible or the impossibility of venturing close) are exacerbated in the case of the sun, which cannot be looked at directly by the human eye. Nevertheless it can be photographed. As early as 1845, there were attempts to photograph the sun, notably the daguerreotypes taken by Léon Foucault and Hippolyte Fizeau, using a lens with a focal length of 10m and a shutter speed of 1/60 of a second. With these images, we are encountering something other than the visual experience offered by Chaves’ stereoscopes, for we do see the sun, spectacularly stripped bare of its corona, it appears “naked”, a round ball, something that human vision can never afford on its own. Sun-photography is heliography in two senses — the early naming of photography as “heliography” (by Niépce) followed an older use of the term to describe knowledge of, or about, the sun.²²

In Plato’s Republic, when the prisoner escapes from the darkness of the underground cave, he is blinded by the luminosity of the exterior world. At first he can only discern shadows, then reflections in water of things and humans, followed by the things themselves, before he is able to lift his eyes upwards to see the constellations and planets in the night sky. Finally, he is able to see the sun “as it is, in its own place”.²³ This gradual opening up of vision and therefore of knowledge leads us to an impossible image. For how can one behold the sun directly without risking blindness? Given that the sun represents the transcendental Good in the sensible world, and is the bestower of vision, how can one look at vision itself?

The sun is that which bestows the image, it is not its subject. By turning the camera on the sun itself, the agency of photography, especially as it was understood in its early years (as heliography or “the pencil of nature”), is reversed. The impudence of this manoeuvre is represented in a cartoon by Félix Nadar, published in the Journal Amusant on 15 January 1858 (Figure 2). It depicts a hot air balloon approaching the sun, a camera pointing directly at its face. This face, rendered expressive by Nadar with a few swift strokes of his pen, is not amused, and, the caption suggests, the sun regrets having lent itself so readily to photography, for the latter has become intrusive: “Le soleil commençant à regretter d’avoir trop fait pour la photographie qui devient indiscrète”.²⁴

Fig. 2. Nadar and Darjou, “Revue du quatrième trimestre de 1858”, Journal amusant, no.159, 15 January 1859, p.1 (Bibliothèque nationale de France)

The balloon, of course, is Nadar’s own, and it is he who offends the sun, by sailing too close, (Icarus-like) but also by rudely pointing his camera directly into its rays. As Peter Buse notes in his article in this issue, Nadar’s pleasure in aerostatic photography seemed as much to do with a pleasure in ballooning, and it was in the sky that (in his own words) he “seems to feel himself really living for the first time”. Buse depicts Nadar as a playful photographer, a thrill-seeker. In his own drawing, Nadar playfully implies (without actually depicting himself) that he is a photographer who has got above his station.

Nadar’s image alludes to ancient stories where proximity to the heavens or the gods is punished. But by turning the camera on the sun itself, Nadar also alludes to this reversal of agency in photography: the camera which might be thought to document or record, to receive the imprint of light as it bounces off objects, instead wants to photograph that which engendered it. For, as the caption suggests, the sun bestows not only vision, but photography itself. The impudence of Nadar’s camera, pointed at the sun, is not only that it comes too close but that it turns the sun’s own instruments on itself: to photograph the sun is to make it into an object of knowledge. Nadar’s photography is heliotropic, he turns toward the sun, he flies too close, but also it raises the question of photography’s tropism, its ability to figure (or to bring to light), when the object being figured is light itself or when the object being figured risks blinding the observer.

Nadar was not the first one to think of aerial photography for cartographic purposes but was the first to realise it. In 1855, Andraud had already imagined this possibility in a satirical piece entitled “Topographie No. 2, Arpentage au daguerréotype”.²⁵ A few months before the publication of his cartoon, Nadar had filed a patent on 23 October 1958 for “A New System of Aerostatic Photography.” He states that photography can be used for “la levée des plans topographiques, hydrographiques et cadastraux, et aussi pour diriger les opérations stratégiques par le lever des fortifications d’une place ou d’une armée en marche, etc.”.²⁶ Nadar’s intention for his aerial photography was clear; it could be used for cartographic purposes and military surveying.

Despite his cartoon, Nadar’s camera did not look up to the sun but down, towards the ground. The proposed perpendicular view would flatten and schematize the land below, rendering it like a map. The playful photographer toys with what he correctly anticipates will become a key element in warfare. In the first world war, aerial reconnaissance photography (from planes rather than balloons), with their emphasis on a vertical viewpoint, would carry out Nadar’s idea. As Tonje Sorenson observed in her paper at the conference, aerial photography became a military technology, or more accurately an “operational framework” involving people on the ground as well as in the air, which did not simply map the terrain but was central in the planning, execution and assessment of the destruction wreaked during the war.

As Sorenson noted, the rhetoric which surrounded this kind of photography emphasized its absolute clarity, its ability to penetrate “the fog of war”, and eulogised the camera as possessed with a rational and impartial perception. Yet Nadar’s first experiments in aerostatic photography had been contaminated in much the same way as Ilford’s plates would be forty years later: through the emission of hydrogen sulphate, in Ilford’s case from the local gasworks, in Nadar’s case from his own balloon. The fogged or blackened plates were unintelligible. The later rhetoric of aerial photography forgot its origins in Nadar’s black collodion plates. It also disavowed the fact that the wartime aerial images were unintelligible except to highly trained observers, who had to “distrust” their imagination, and study the photographs using exact geometrical measures.

In their article included here, Dvořák and Parikka discuss how a “regime of knowledge practices [is] embedded in aesthetic practices”. We can see this in aerial reconnaissance but also in the way that ideas about racial and geographic difference are linked to the photographic materials industry’s calibrations and calculations designed to moderate and manage light and heat in the darkroom, specifically in the so-called tropics. The hot and humid parts of the British Empire were understood in European colonial discourse as “the tropics” regardless of their specific geographic location: regions whose nature and people were designated “backward” and “intemperate”, and “lacking in moderation, control, regulation”.²⁷ The archives of Ilford Limited and the British Journal of Photography show how photography in the so-called tropics was conceived as particularly arduous, with the heat and moisture producing difficulties that are only outstripped by the extreme environment of the polar expeditions described by Watkins. The industry catered to photographers in the tropics with new products (such as Ilford’s Tropical Hardener) and a burgeoning advice literature. These advocated specific standards for the tropical darkroom, including development times and dilution ratios of chemicals tailored to the heat, via a discourse that simultaneously (re)produced the tropics as “difficult” and “excessive”.

At the same time, descriptions by photographers in “the tropics” of their darkroom experiences are both ludic and ludicrous: one writer in 1922 describes the “joys” of his improvised darkroom in “tropical West Africa” as involving interruption by lightning and rain and especially, by local wildlife,

“One huge specimen of horned beetle buzzed in with a bang, and smashed the lamp-glass to atoms. Another of the same species collided with one of the expedition in the darkness, and gave him a lovely black eye. It is a very pleasant sensation to be loading film and hear the unmistakable rustle among the reeds of floor of some creepy crawly thing, then whack! a lizard falls out of the roof on to your bare shoulders”.²⁸

The mode of description is both ironic and playful, delighting in entertaining the reader with the horrors of this lively darkroom.

As Peter Buse notes in his article here, we find the ludic in photography, not simply in playful or funny images, but in the doing of photography, the rituals and rules of the photographing community, the thrills and dangers of photography against the odds, of sailing too close to the sun. If in photography theory an association of photography with death has, as Buse proposes, “overshadowed […] the play element in photography”, there is also a sense of the ludic within these meditations on death. For example, in Athens, Still Remains, Derrida compares himself to to an amateur photographer, who is allowed to experiment and make mistakes, making multiple exposures with zoom lenses, thus creating disjointed close-ups of the same location, retracing his footsteps, catching a shadow by surprise, making polaroids and stéréotypes, and yet he can always admit to his lack of experience with his clumsy framing (cadrage maladroit), overexposure (surexposition), underexposure (sous-exposition) of the image or pointing his camera directly into the light (effets de contre-jour).²⁹

This always-already-there of the photographic, which we have suggested here and which some of the papers in this special issue touch on, is what Derrida describes as an “invasion of photography” into history. In Athens it appears to him as “An absolute mutation, though one prepared from time immemorial (physis, phôs, hêlios, teknē, epistēmē, philosophia).”³⁰ Under the scorching heat of the Athenian sun, we see how photography and philosophy are intertwined in the “luminous memory of Athens” . Looking out from the promontory of Cape Sounion before descending to meet his friends for a swim at the foot of the temple, he finds himself standing on the same spot, where once a ship came into view—a ship returning from its annual pilgrimage to Delos — a ship that is late. For Derrida, the appearance of the luminous sails signalling and setting into motion Socrates’ death by pharmakon is photography, “I am thinking of the death of Socrates, of the Phaedo and the Crito. Of the incredible reprieve that delayed the date of execution for so many days after the judgment. They awaited the sails, their appearance off in the distance, in the light, at a precise, unique, and inevitable moment — fatal like a click.”³¹

Funding

The conference from which this Special Issue developed was supported by AHRC funding awarded to Michelle Henning under [grant number AH/R014639/1].

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The conference from which this Special Issue developed was supported by AHRC funding awarded to Michelle Henning under [grant number AH/R014639/1].

Notes on contributors

Michelle Henning

Michelle Henning is Professor in Photography and Media at the University of Liverpool.  She writes on modernism, new media, museums, and the history and theory of photography, and also works as an artist and designer. She has published many chapters and articles on photography, and her book Photography: The Unfettered Image was published in 2018.  She recently completed an AHRC leadership fellowship drawing on the archives of Ilford Limited, resulting in several current and forthcoming articles including “The Worlding of Light and Air: Dufaycolor and Selochrome in the 1930s”, in Visual Culture in Britain (2020).

Junko Theresa Mikuriya

Junko Theresa Mikuriya is Senior Lecturer in Photography at the London School of Film, Media and Design, University of West London. She worked as a freelance photographer in the fashion and music industries, specializing in album covers and fashion editorial work in Asia and Europe, including Taipei, Hong Kong and London. She has a PhD in Cultural Studies from Goldsmiths University of London and a Maîtrise de Lettres Modernes from Sorbonne, University of Paris IV.  She is the author of A History of Light: The Idea of Photography (Bloomsbury 2016), a book that investigates the relation between photography, light and philosophy.

Notes

1. Cophenhaver, “Hermes Trismegistus, Proclus, and the Question of a Philosophy of Magic in the Renaissance,” 103–4.

2. The full set of papers from the conference, in the form of audio files, can be found at the following link: https://backdoorbroadcasting.net/2019/12/light-sensitive-material/

3. Cadava, Words of Light, 5.

4. In the Platonic universe, the sun is seen as the symbol of the transcendental Good in the sensible world. Derrida writes that the sun is simultaneously the paradigmatic natural object and “already and always metaphorical” (53). Since “There is only one sun in this system”, it becomes “the father of all figures of speech. Everything turns on it, everything turns to it”: everything then, is heliotropic. Derrida, “White Mythology: Metaphor in the Text of Philosophy,” 44.

5. See Kingsley, In the Dark Places, 78–84.

6. Catford, Our first 75 years, 50. See also Hercock and Jones on the controlled air systems and filtrations systems used to prevent contamination in Ilford’s factories. Hercock and Jones, Silver by the Ton, 35–140.

7. Collodion, first adopted for photographic purposes in 1851, in Frederick Scott Archer’s wet-plate collodion process, was also deployed in medicine as an “artificial skin”, to heal wounds and cosmetically disguise skin disorders or scars. Celluloid was patented in the 1860s, and adopted for manufacturing the flexible film base for cinematography and photography. Cellulose remains a key ingredient in photography, not only in films but in papers. Elizabeth Howie’s article included here mentions plant-based papers including rag papers made using cotton and linen and papers derived from trees.

8. Barthes, Camera Lucida, 6.

9. Mikuriya, A History of Light, 1.

10. Shiff, “Phototropism (Figuring the proper),”163.

11. Ibid., 164.

12. Gil-Fournier argued that Wiesner’s use of photography, and the application of his work to agriculture (accelerating plant growth) shows how “photography becomes infrastructural in the reshaping of life”. Gil-Fournier, “The Vegetal Calculated Image.”

13. Derrida, Copy, Archive, Signature, 43–4

14. As Mikuriya argues, “These instances of the photographic should not be considered metaphors but rather intimations of photography.” See History of Light, 121.

15. De Mysteriis, III.14, 132.9–12. In fact the history of Western philosophy can be read as the movement of photagogia in which photography is considered as a mode and practice of the latter. See Mikuriya, History of Light, 7.

16. Sarah Iles Johnston notes that “phantaskitē dunamis” can be defined literally as the “ability of the vehicle to receive or process images.” See Johnston, “Fiat Lux, Fiat Ritus,” 17.

17. Marks, “A Radical Indexicality”.

18. For the notion of epitēdeiotēs see Shaw, Theurgy and the Soul, 86 and “Containing Ecstasy: The Strategies of Iamblichean Theurgy.”

19. De Mysteriis, III.14, 12–15.

20. Derrida, “White Mythology”; and Shiff, “Phototropism.”

21. Dos Reis, “Smoke, Steam and Lava” .

22. This use dates to at least the turn of the 19th century: “the knowledge which treats of the sun is called heliography” — Hall, The creation, in six books after the manner and as an introductory. Geoffrey Batchen also points to a 1798 text by Charles Palmer, which claims the sun is made of ice, and used heliography to describe the science concerned with the study of the sun. Batchen, “The naming of photography.” Later, heliography described the practice of using an instrument — the heliograph, sometimes called a sun telegraph, that was developed in 1875 for communicating Morse code messages with mirrors and sunlight. It was principally used in military and colonial contexts, though some histories trace to Southwestern native American techniques, it was appropriated in the US army for use against the Apaches. Sterling, Christopher H., ed. Military Communications: From Ancient Times to the 21st Century. Oxford: ABC-CLIO, 2007, 210.

23. Plato, Republic (516b).

24. “The sun was beginning to regret having done too much for photography, who was becoming impudent.”

25. For a detailed discussion of Nadar’s ventures in aerial photography, see Gervais, “Un basculement du regard.”

26. “Brevet d’Invention de Quinze Ans, au sieur Tournachon, à Paris, Pour un nouveau système de photographie aérostatique,” Bouchard-Huzard, Descriptions des machines, 144.

27. Henning, “The worlding of light and air,” 181–2. As with terms like “heliotropic” and “phototropic”, the term “tropics” comes from the Ancient Greek tropē, and referred originally to “turning” of the sun.

28. Dykes, “Photography in Tropical West Africa,” 310.

29. Derrida, Athènes à l’ombre, 40.

30. Derrida, Athens, Still Remains, 6.

31. Ibid., 29.