Photographic Exposure Research Articles

Experimental validation of the presence of flow maldistribution in electrodialysis stacks and its effect on the limiting current density

Flow maldistribution between channels in electrodialysis has previously been simulated and is predicted to have a substantial impact on the limiting current density (LCD) and thus constitutes a barrier to industrial implementation. Using computational fluid dynamics (CFD) simulations and a 1-D circuit-based model, it was previously concluded that maldistribution is both prevalent in electrodialysis and adversely affects operation through a reduction of the LCD. In this work, the presence and impact of maldistribution are confirmed experimentally using red-blue particle image velocimetry (PIV) and through measuring the LCD as a function of the degree of maldistribution, respectively. In the PIV experiments, 50 μm particles were suspended and were flowed through a glass flow cell with the same geometry as those used in the CFD simulations. These spheres were imaged using a single exposure photograph and two pulsed LED bursts and their velocities subsequently calculated. The imaging of many particles demonstrated significant maldistribution in line with what had been previously predicted. The effect of maldistribution on operation was experimentally validated by measuring the LCD of an electrodialysis stack as a function of the degree of maldistribution. The degree of maldistribution was independently controlled by varying the flow rate and the number of cell pairs while accounting for confounding effects. The measured LCD was found to decrease with an increasing degree of maldistribution. A further CFD study was performed, comparing the degree of maldistribution in U and Z configuration stacks. It was demonstrated that while at low flow rates, maldistribution is worse for U-type geometries, at high flow rates, it is worse for Z-type geometries. Overall, the results presented in this work conclusively demonstrate that maldistribution exists within electrodialysis and significantly affects the LCD. This consequently validates previous modelling results and highlights maldistribution as an important phenomenon in electrodialysis that should be considered when optimisation is performed.

Contact with nature through virtual reality and video: An effective solution for improving self-esteem in adults

Abstract It is widely acknowledged that exposure to natural environments offers emotional, cognitive, and behavioural benefits. However, some individuals may face difficulties in accessing these areas frequently and conveniently due to urbanisation, disability, or a lack of time. As a result, research has explored the advantages of nature substitutes, such as photographs, videos, or virtual reality (VR), and has demonstrated their ability to provide psychological benefits. Therefore, our study aims to examine the impact of these substitutes on enhancing individuals’ self-esteem. The study involved 236 participants, who were divided into six experimental groups based on the type of exposure (photographs, video, or virtual reality) and the environment (natural or urban). A control group was also exposed to geometric shapes. The participants completed the French version of the Rosenberg Self-Esteem Scale three times: upon arrival at the experimental room (baseline), after the rumination induction task (post-induction), and after exposure (post-exposure). The analysis focused on changes in self-esteem scores during the experimental study, considering the type of exposure and its content. The results suggest that exposure to nature, in any form, enhances self-esteem more than exposure to urban environments or geometric shapes. Additionally, it was found that virtual reality or video exposure to nature produced greater benefits than natural photographs. In the future, alternative tools may serve as valuable support for individuals who are unable to experience direct contact with nature. However, it is important to recognise that they should be considered as supplementary options rather than exclusive substitutes.

Aesthetics exploration of chiaroscuro light: capturing the visual atmosphere of traditional markets in Jakarta

Photography is needed as a medium of expression and delivery of communication messages. In the field of art, Chiaroscuro is a new vehicle for expression to be translated as a visual object in creating street photography. The main focus that is interesting to know is about the aesthetics of chiaroscuro light in the art of photography. The purpose of this research is to describe how to visualize the aesthetic expressions of researchers about traditional markets in the area of Jakarta. The research method employs an artistic approach within the context of visual field research, emphasizing creativity, subjective perspectives, and interpretations. The analysis techniques center on formal aspects of visual elements, including composition, color, shape, line, and texture, with the goal of understanding how these elements contribute to the overall aesthetic and communicative qualities of the image. Photographic exposure and description are supported by subjective observations. The results of the study show that photography is able to provide aesthetic expression according to the wishes of the researcher. The research contributes to the field by exploring the use of chiaroscuro as a novel expressive tool in street photography, particularly in the context of traditional markets in Jakarta. It demonstrates how an artistic approach and formal visual analysis techniques can effectively capture and convey the aesthetic qualities of these markets, ultimately resulting in a tangible outcome in the form of a photo book, enriching our understanding of urban culture and visual communication.

An Automated Hemispherical Scanner for Monitoring the Leaf Area Index of Forest Canopies

The leaf area index (LAI) is an important structural parameter of plant canopies used in terrestrial biosphere models. Optical methods are commonly used for measuring LAI due to their non-destructive nature, convenience, and rapidity. In the present study, a novel instrument, named the Automated Hemispherical Scanner (AHS), was developed to measure plant area index (PAI) for monitoring daily changes in LAI in forest ecosystems. In the AHS, an optical sensor driven by a pair of servomotors is used to observe hemispherical light transmission continuously at adjustable intervals, and a blue filter is used to reduce the multiple scattering effect of light on the measured transmission. A set of algorithms was developed to screen the direct radiation transmitted through the canopy and to compute the transmissions from the diffuse radiation at seven zenith (0–60) and seven azimuth (0–150) angles for calculating PAI. Field experiments were conducted to verify the reliability of the AHS in three forests of Northeast China against an existing instrument named the LAI-2200 Plant Canopy Analyzer. The PAI values obtained using the AHS agreed well (R2 = 0.927, root mean square error = 0.41) with those from the LAI-2200. Since both instruments use the same gap fraction theory for calculating the PAI from diffuse radiation transmissions obtained from multiple angles, the agreement of these two instruments means that the AHS can reliably measure the transmittance of diffuse radiation and the theory has been implemented correctly. Compared with LAI-2200, the AHS has the advantage of automated and continuous measurements, and therefore it is suitable for monitoring variations in PAI over extended periods, such as the whole growing season. Compared with widely used digital photographic techniques, the AHS also avoids the requirement of determining a suitable photographic exposure, which is often problematic in the field with variable sky conditions. With these advantages, the AHS could be deployed in forest growth monitoring networks.

Media Primitivism: Technological Art in Africa By Delinda Collier

Media Primitivism: Technological Art in Africa By Delinda Collier

Victorian Negatives: Literary Culture and the Dark Side of Photography in the Nineteenth Century, by Susan E. Cook

Reviewed by: Victorian Negatives: Literary Culture and the Dark Side of Photography in the Nineteenth Century by Susan E. Cook Lindsay Smith (bio) Victorian Negatives: Literary Culture and the Dark Side of Photography in the Nineteenth Century, by Susan E. Cook; pp. xxxiv + 183. Albany, New York: State University of New York Press, 2019, $95.00, $32.95 paper. Photographic negatives are enigmatic things. They have become increasingly so with the shift to digital technologies. Celluloid reels with hole-punched edges pegged up to dry appear as but a memory of the red-lit darkroom, evoking the magic of that cell-like space. Susan E. Cook’s richly evocative Victorian Negatives: Literary Culture and the Dark Side of Photography in the Nineteenth Century is rooted in the physical experience of the practitioner inhabiting that realm of developer, stop, fix, and wash, where exposure times and the material concerns over paper quality and chemical dilutions hold primary importance. At the same time, the book deals with less tangible qualities that haunt and emerge from the darkroom and that continue to infuse visual and verbal spheres long after that dark physical space has become unfamiliar to many. [End Page 442] The introduction sets out Cook’s approach that considers material and figurative qualities of the negative and the ways in which “the meanings it produces are articulated directly and indirectly through literary culture” (xxi). Her contention that “the photographic negative has shaped the way we see in ways we no longer see” has the appeal of being both obvious and not obvious at all (xxx). As Cook demonstrates, this claim brings with it a raft of questions about perceptual mediation, including photographic remediation by varieties of negatives together with their complex conceptual implications. The book’s five chapters are organized around literary texts by Charles Dickens, Arthur Conan Doyle, E. W. Hornung, Robert Louis Stevenson, Oscar Wilde, Thomas Hardy, and Bram Stoker. Chapter 1 addresses the direct positive process of the daguerreotype in relation to Dickens’s A Tale of Two Cities (1859), exploring what the daguerreotype cannot do in the manner of the negative/positive process: namely, generate multiple copies of an original and restore the lateral inversion of the mirror. The literary analysis, along with discussion of the illustrations by Hablot K. Browne (“Phiz”), is tied closely to the discomfort Dickens felt in having his photograph taken, which for him amounted to “a counterfeit presentment” (2). Cook further explores, in the context of literary celebrity, Dickens’s “anxiety” about a lack of control over the reproduction of his image, and the negative’s capacity to generate positives without the subject’s knowledge (3). Such concern over control of one’s portrait is taken up in the third chapter in terms of the forensic photograph and the cabinet card. Cook agrees with Tom Gunning that, for Conan Doyle, “the world of the detective and the world of spirits were not [necessarily] incommensurate” (56), since “photography allowed one to see what had not been seen before” (55). While arguably the least compelling of Cook’s chapters—photography in Doyle’s “A Scandal in Bohemia” (1891) is well-trodden territory—it introduces fascinating material such as Alexandre Dumas’s “horror” (63) of being photographed and his comparison of the mid-nineteenth-century habit of giving photographic portraits “to those who ask for them” with the giving of “alms to a mendicant” (64). In addition to enabling the indiscriminate dissemination of photographs, negative/positive processes corrected the inversion of daguerreotypes; multiple implications of inversion are key to the book. In several nimble readings, Cook charts the impact of the negative’s reversal of light and dark. Chapter 4, for example, takes up what we might think of as an aberrant, albeit often crafted, effect in the form of the double exposure. Cook frames her discussion in terms of the literary double negative, whose “syntactical structure” she claims resembles the combined “negative elements” of the photographic double exposure (74). The chapter ranges widely from short fiction and spirit photography to Strange Case of Dr Jekyll and Mr Hyde (1886) and The Picture of Dorian Gray (1890) as pervaded by a photographic logic of “duplication and...

High Contrast Ultrathin Light‐Field Camera Using Inverted Microlens Arrays with Metal–Insulator–Metal Optical Absorber

AbstractLight‐field imaging has attracted much attention in constructing 3D objects with a simple configuration and capturing all the spatial and directional data in a single photographic exposure. Here, an ultrathin light‐field camera (ULFC) for high contrast and high‐resolution light‐field imaging using a metal–insulator–metal optical absorber based inverted microlens arrays (MIM‐iMLA) is reported. A metal–insulator–metal based optical absorber (MIM‐OA) between microlenses exhibits high light absorption in the full visible region, thereby highly blocking microlens crosstalk. The MIM‐iMLA double the image contrast and improve MTF50 by up to 32%, compared to conventional light‐field image. In addition, the MIM‐iMLA substantially reduces an image plane distance and brings the objective lens position closer to the MLA. The ULFC exhibits a short total track length of 5.1 mm, demonstrating high contrast light‐field image acquisition and high accuracy 3D depth map estimation after light‐field rendering. This ultrathin and high contrast light‐field camera can provide a new platform for miniaturized 3D cameras in biomedical applications, biometrics, automated inspection, or mobile camera applications.

El Año Nuevo aymara de Cancosa (Tarapacá, Chile). Reciprocidad complementaria y etnogénesis a través de foto-etnografía.

Through a photo-ethnography on the Machaq Mara (Aymara New Year) celebration at the border community of Cancosa in Northern Chile, we reveal how an ethnogenesis process operates. We suggest that the central-Andean foundational principle of complementary reciprocity plays a fundamental role in this process. Our methodology consists of a visual reflective approach through photographic exposure, made possible through a combination of observant participation, the review of archives and interviews on the contemporary genesis of the festivity in Chile. We propose that the Machaq Mara celebration represents a preferential analytical space to identify dynamics of local ethnogenesis, in which ritual complementarity, as well the role of the State and indigenous officials in its process.

Parameters optimization of light field micro-particle image velocimetry

The light field micro-particle image velocimetry (LF-μPIV) can record the instantaneous three-dimensional (3D) spatial position information of tracer particles in a single photographic exposure by a single camera, and thus achieve the instantaneous 3D velocity measurement of the micro-scale flow. The accuracy of the spatial positions of the reconstructed tracer particles is closely related to the spatial reconstruction resolution of the LF-μPIV system, and determines the measurement accuracy of the 3D velocity distribution. In this paper, the effects of the optical parameters of the LF-μPIV system and the spatial position of the tracer particle on the spatial resolution and reconstruction quality are numerically studied. The location of the measurement volume and the optical parameters of the LF-μPIV system are further optimized. Based on the optimized parameters, a LF-μPIV system is assembled. Finally, experiments are carried out to verify the feasibility of the optical parameters optimization from simulations and to evaluate the performance of the LF-μPIV system for three-dimensional velocity field in a micro-scale convergent channel. Results indicate that the lateral and axial reconstruction resolutions are higher in the outside and inside regions away from the focal plane, compared with those in the region near the focal plane of the objective lens, and is less affected by the microlens aperture, CCD sensor pixel size and objective lens magnification. The spatial reconstruction resolution of the LF-μPIV system at different depths is in good agreement with the simulation results, proving the effectiveness of the optical parameters optimization of the LF-μPIV system. The measurement results of 3D velocity field in a micro-scale convergent channel are consistent with the simulation results by ANSYS Fluent, further verifying the feasibility of the optimized LF-μPIV system for 3D velocity field.

NOISY FIELD EXPOSURES, or what comes before attunement

Before attunement comes exposure, the necessary fact of being a body. This photo essay is a play on two meanings of the word exposure: corporeal exposure and photographic exposure. I offer the latter in order to stay with moments of the former, exposing multiple scenes of misattunement from fieldwork in a small country town in regional Australia. Picking up the classic distinction in information theory between signal and noise, this piece pauses at the moment of indeterminacy before an event might be affirmed as valuable signal or discarded as unwanted static, weaving stories and images from the field with excerpts from Michel Serres’ The Parasite, Roland Barthes’ Camera Lucida and Paul Harrison’s essay on Corporeal Remains. Ultimately, this essay’s suggestion is that ‘attunement’ is not primarily about attunement. Instead, as a methodological principle, I offer that attunement initially – and sufficiently – gestures towards an attempt, a vulnerability and a commitment to the event of exposure.

A Microparticle Image Velocimetry Based on Light Field Imaging

Accurate 3D flow characterization in a microchannel is becoming increasingly important for the design and development of microfluidic chips. In recent years, a light held camera that can simultaneously record the direction and position information of rays in a single photographic exposure has been developed and employed in the held of computer graphics. In this paper, a microparticle image velocimetry based on light held imaging (light held μPIV) is proposed to reconstruct the 3D velocity held of a microscale flow. Both simulations and experiments are performed to verify the proposed method. The light held image of tracer particles and the point spread function (PSF) of a light held microscopic imaging system are numerically calculated based on the Abbe imaging principle. The 3D positions of the tracer particles in a flow held are then reconstructed by the Lucy-Richardson 3D deconvolution algorithm. Furthermore, a light held μPIV system based on an assembled cage light held camera with a microscope is developed, and calibrations are performed to obtain the geometric parameters of the μPIV system accurately. The simulation and experimental results demonstrate the feasibility of the proposed light held μPIV. Compared with the synthetic refocusing reconstruction method, the Lucy-Richardson 3D deconvolution algorithm greatly improves the lateral and the axial resolutions of the flow held.

Medium, calculation, play: On digital images in scientific practice

Latour’s notion of immutable mobiles relates the circulability of certain objects to, among other features, their immutability, readability and combinability. As such it does not distinguish between, say, hand-drawn maps and machine-generated graphs. How, though, does the medial ‘microstructure’ of immutable mobiles matter to socially shared uses? Would, for example, digital images as bounded grids of nonoverlapping square pixels, each representing a numerical value, shape how distributed scientific work unfolds? In this article, I begin with reviewing attempts to link the microstructure of media to their communicative uses, focusing on Luhmann’s relational account of media as loosely coupled substrates in which more rigid forms can become manifest. Drawing on an ethnography of astronomical research, I then inquire into how the scientists involved reasoned about their uses of media from within their practices. They used digital photographic exposures as ‘workable objects’ whose usefulness was not guaranteed initially. Local work was oriented to potential reuses of images (as processed exposures) by researchers elsewhere, as demonstrated by concerns over the integrity of images, the possibility of describing their work with reasonable efforts, as well as by negotiating acceptable elements in calculations so as to reveal stabilized phenomena. In doing so, scientists insisted on the need to play or experiment, suspending sequential work for explorations oriented toward deciding which action among alternatives to make consequential. This was part of a more extended ‘calculative game’ that points, through its orientation to reasonable agreement and delimitations of legitimate efforts, to the social order of this work. The medium, here conceived as images deemed accountable to reuses elsewhere, is a social achievement. Recognizing this may help to better understand the reusability of scientific data and its challenges.

The Influence of Different Factors on the Dual Atmosphere Effect Observed for AISI 441 Interconnects Used in Solid Oxide Fuel Cells

Interconnects used in solid oxide fuel cells are subjected to dual atmosphere corrosion at 600 °C. In this work we show that the dual atmosphere effect is dependent on the thickness of the steel sheet. For this AISI 441 with varying thicknesses was exposed to dual atmosphere at 600 °C for 336 h. Before and after exposure photographs were taken to analyze the progress of corrosion on the air-facing side of the steel samples. Additionally, scanning electron microscopy and energy dispersive x-ray diffraction (SEM/EDX) analysis was conducted on all exposed samples. It was found that thinner samples showed increased breakaway oxidation than thicker samples.

Sky-canopy border length, exposure and thresholding influence accuracy of hemispherical photography for complex plant canopies

BackgroundHemispherical photography (HP) is a popular method to estimate canopy structure and understorey light environment, which analyses photographs acquired with wide view-angle lens (i.e. fisheye lens). To increase HP accuracy, the approaches of most previous studies were to increase the preciseness of exposure and thresholding of photographs, while ours quantified effects of canopy properties (gap fraction and length of sky-canopy border (SCB)) and errors of exposure and thresholding on the accuracy of HP.ResultsThrough analysing photographs of real and model canopies, it was showed that HP inaccuracy resulted from the mismatch between exposure and thresholding rather than exposure or thresholding errors alone. HP inaccuracy was a function of the SCB length and the extent of exposure and thresholding errors, but independent of gap fraction.DiscussionIn photographs, SCBs are recorded as grey pixels which greyness is in between that of sky and canopy pixels. When there are exposure and thresholding errors, grey pixels are those prone to be misclassified in image analysis. Longer (vegetation with taller canopies) and wider (lower image sharpness) SCBs in photographs can both result in a higher amount of grey pixels and ultimately higher HP inaccuracy for a given extent of exposure and threshold errors.ConclusionsUsing lenses with view angle narrower rather than that of fisheye lens can shorten the SCB length in photographs and in turn reduce HP estimation inaccuracy for canopy structure and understorey light environment. Since short SCBs and low levels of exposure and thresholding errors can both result in low HP inaccuracy, to identify the true performance of new exposure and thresholding methods for HP, photographs recording canopies with long SCBs and acquired with fisheye lenses should be used. Because HP inaccuracy in a function of the amount of grey pixels resulting from SCBs, the amount of these pixels in photographs can be used as a universal parameter to quantify canopy properties influential to HP estimation and in turn make cross-study comparisons feasible.

Selenium and tellurium nanomaterials

Abstract Over the last 40 years, the rapid and exponential growth of nanotechnology led to the development of various synthesis methodologies to generate nanomaterials different in size, shape and composition to be applied in various fields. In particular, nanostructures composed of Selenium (Se) or Tellurium (Te) have attracted increasing interest, due to their intermediate nature between metallic and non-metallic elements, being defined as metalloids. Indeed, this key shared feature of Se and Te allows us the use of their compounds in a variety of applications fields, such as for manufacturing photocells, photographic exposure meters, piezoelectric devices, and thermoelectric materials, to name a few. Considering also that the chemical-physical properties of elements result to be much more emphasized when they are assembled at the nanoscale range, huge efforts have been made to develop highly effective synthesis methods to generate Se- or Te-nanomaterials. In this context, the present book chapter will explore the most used chemical and/or physical methods exploited to generate different morphologies of metalloid-nanostructures, focusing also the attention on the major advantages, drawbacks as well as the safety related to these synthetic procedures. Graphical Abstract: Overview of the chemical and physical methods commonly used to produce various Se- and/or Te-based nanomaterials.

Successful single treatment with ziv-aflibercept for existing corneal neovascularization following ocular chemical insult in the rabbit model

PurposeTo evaluate the efficacy of ziv-aflibercept as a treatment for established corneal neovascularization (NV) and to compare its efficacy to that of bevacizumab following ocular chemical insult of sulfur mustard (SM) in the rabbit model. MethodsChemical SM burn was induced in the right eye of NZW rabbits by vapor exposure. Ziv-aflibercept (2 mg) was applied once to neovascularized eyes by subconjunctival injection while subconjunctival bevacizumab (5 mg) was administered twice a week, for 3 weeks. Non-treated exposed eyes served as a control. A clinical follow-up employed by slit-lamp microscope, was performed up to 12 weeks following exposure and digital photographs of the cornea were taken for measurement of blood vessels length using the image analysis software.Eyes were taken for histological evaluation 2, 4 and 8 weeks following treatment for general morphology and for visualization of NV, using H&E and Masson Trichrome stainings, while conjunctival goblet cell density was determined by PAS staining. ResultsCorneal NV developed, starting as early as two weeks after exposure.A single subconjunctival treatment of ziv-aflibercept at 4 weeks post exposure, significantly reduced the extent of existing NV already one week following injection, an effect which lasted for at least 8 weeks following treatment, while NV in the non-treated exposed eyes continued to advance. The extensive reduction in corneal NV in the ziv-aflibercept treated group was confirmed by histological evaluation. Bevacizumab multiple treatment showed a benefit in NV reduction, but to a lesser extent compared to the ziv-aflibercept treatment. Finally, ziv-aflibercept increased the density of conjunctival goblet cells as compared to the exposed non-treated group. ConclusionsSubconjunctival ziv-aflibercept single treatment presented a highly efficient long-term therapeutic benefit in reducing existing corneal NV, following ocular sulfur mustard exposure. These findings show the robust anti-angiogenic efficacy of ziv-aflibercept and demonstrate the advantage of this treatment over the other anti-angiogenic therapies in ameliorating corneal NV and protecting the ocular surface.

Оценка индивидуально-психологических свойств человека в зависимости от конфигурационных изменений его лица

Introduction. The study examines the relationship between facial configuration and assessing personality traits. Objective determinants of interpersonal perception, such as facial types, a model’s age and gender, the mode and duration of exposure of facial photographs, etc., are well elaborated in domestic and foreign studies. However, questions remain about how facial structure and also the observer's personality characteristics determine the perception of individual psychological characteristics through facial photographs.
 Methods. The study employed the comparative analysis of evaluations of individual psychological characteristics by facial photographs by the scales of the Personal Differential Questionnaire in combination with multidirectional transformations of photographs of neutral faces.
 Results. A systematic variation of four configuration variables – location of the mouth and eyes, nose length, and pupillary distance – not only causes weak persistent impressions of joy or sadness, but also changes ideas about individual psychological traits. The induced joy was associated with the positive poles of the scales of the Personal Differential Questionnaire; the induced sadness was associated with the negative poles of its scales. Directional transformations had different impacts on ideas about the components of the implicit structure of personality – evaluation, potency, and activity. Extraversion was more often associated with female faces, while the perceived dominance/subordination – with male faces. The observed patterns modified under the influence of facial morphotypes and the observer’s self-assessment.
 Discussion. The research findings confirm an overgeneralization of weak emotional states when perceiving neutral faces and indicate a close association between overgeneralization and the observer’s self-concept.
 In conclusion: a multidirectional variation of the configuration variables of emotionally neutral faces selectively affects the perception of personality traits. The observer’s sympathy/antipathy and also his/her individual psychological features play a special role in assessing the personality characteristics through facial expressions.

Threshold determination by reference to open sky overcomes photographic exposure error in indirect leaf area index estimation

Threshold determination by reference to open sky overcomes photographic exposure error in indirect leaf area index estimation

Estimating light environment in forests with a new thresholding method for hemispherical photography

Light environment estimates derived from hemispherical photography are known to be affected by variations in sky illumination. During photo acquisition, rapid changes in sky illumination can occur and will result in changes in detected canopy gap size and frequency. Any resulting problems in image consistency will become more serious with increased time lags between setting the reference exposure and hemispherical photograph acquisition. We showed that if the camera exposure setting was kept constant during photo acquisition, the estimated diffuse transmittance would be greatly influenced by sky illumination change. We developed a new pixel thresholding method that calculated the optimal threshold value for the separation of sky and plant pixels as a function of the above-canopy photosynthetic photon flux density (PPFD). We tested the performance of our method for estimating transmittance against two established methods that assume exposure to be held constant to two stops higher than the reference exposure. Our method compensates for changes in sky illumination, producing a smaller pixel threshold value when sky illumination decreases and a larger pixel threshold value when photographs are taken under increased sky illumination. The new method achieved accurate and reproducible results, even in situations where under- or over-exposure was caused by changes in sky illumination during photo acquisition.

Illuminated paths: Using light to draw the intermovemental stages of skateboarding tricks

Abstract By interrogating built form and using intuitive and artistic understandings of space to carve out new landscapes, skateboarders demonstrate how urban space can function in alternative ways. This article explores a way of capturing the divergent contours, peaks and valleys of skateboarders’ paths through space as a series of drawings that not only map variations of urban landscape, but also act as an expression of individuals’ experiential moments in time. My discussion focuses on the work of Buzzy Sullivan, a skateboarder and artist living in Oregon, USA, who shoots long exposure photographs of an LED light-clad skateboard during different skate tricks. In the resulting images the movement of the skateboard appears as a series of drawn light paths, resembling a 3D contour map of an alien terrain. Although these ephemeral light lines have obvious advantages due to their ability to make the sheer variation in contours of movement through space visible, they are reliant on photography for their preservation. Positioned as drawings, the lines of light enable us to visualize how skateboarders navigate environments and provide the DNA strands of each trick as it is being performed. These are drawings about the process of their own creation, acting as a fluid process that awakens new possibilities for sculpting and reading the city. I suggest that Sullivan’s images provide a method for research that captures the nuanced ‘intermovemental’ stages of skateboarding as drawings that help to explain what happens between the board and the ground in a skateboarder’s cartographic constitution of place.