COLOUR GROUP STUDENT AWARDS

Transcription

1 Living opals in brown algae. COLOUR GROUP STUDENT AWARDS 2017 Nathan J. Masters 2, Martin Lopez-Garcia 1, Heath E. O Brien 2. Joseph Lennon 3, George Atkinson 3, Martin J. Cryan 1, Ruth Oulton 1, Heather Whitney 2. 1 Department of Electrical and Electronic Engineering, University of Bristol, Bristol, BS8 1TH, UK. 2 School of Biological Sciences, University of Bristol, Life Sciences Building, 24 Tyndall Avenue, Bristol, BS8 1TL, UK. 3 School of Physics, HH Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol, BS8 1TL, UK. We present the first example of a naturally occurring 3D photonic crystal in algae, in particular the brown algae Cystoseira tamariscifolia. Through in-vivo spectroscopy, modelling, and microscopy methods, we have characterised and demonstrated the origin of the strong blue colouration of the algae: the intracellular, opal-like arrangement of lipid nanospheres. The position of these living opals near the surface and in close proximity to chloroplasts suggests a role in which these vesicles modulate the light experienced by the chloroplasts for light harvesting or photo protection. We will also show preliminary data on the dynamic nature of this structural colour in response to environmental illumination which adds further significance to these findings. 1

2 a) Cryo-SEM image showing the location of a living opal within an epidermal cell; b) CryoSEM image showing the arrangement of nanospheres within the vesicle; c) Confocal fluorescence image showing the positions of living opals (red, arrow) surrounded by chloroplasts (green); d) Low magnification image of a specimen of C. tamariscifolia demonstrating the pointillistic blue-green colouration. 2

3 Becky Gooby, PhD Researcher UWE Bristol, 3D3 Centre for Doctoral Training Research: The development of methodologies for digital colour printing in textile design Awarded WD Wright to present and attend Textiles & Life. Survival to Fashion and Everything In Between The Textile Institute Student Conference, Manchester UK 22nd November 2017 Conference Abstract My research considers how designers can ensure colour fidelity when digital textile printing on a range of fabrics, by exploring and developing existing colour tools and methods. The aim is to produce an online tool kit which practitioners and SMEs can draw upon to develop their digital colour knowledge, alongside tested techniques which they can utilise to achieve the colours they expect. Digital screen colour, a mix of red, green and blue light, has a broader colour range to digitally printed colour, principally a mix of cyan, magenta, yellow and black (CMYK) primaries. Design software allows a user to select colours from the screen that cannot be printaed using CMYK colorants, which can be frustrating, and confusing, when printed designs don t match what is seen on screen. Additionally, colour results are affected by factors such as structure and composition of the fabric, dye type, printer communications, fabric pretreatments and secondary processes (washing and steaming). A textile designer will be required to understand and experiment with a number of variables in order to feel confident about the outcome. I began engaging with digital print in 2008 when studying for a Masters in Textile Design. I encountered colour issues, particularly when printing across substrates, which I didn t know how to resolve. Further investigations established that many freelancers and SMEs, without access to expensive and technical equipment, struggled to comprehend the colour process. Consequently, I set out to establish ways that designers, like myself, could navigate this technology so that the creative and entrepreneurial possibilities of digital textile printing may be exploited. These initial inquiries led me to undertake a PhD at the Centre for Fine Print Research, UWE, Bristol. My PhD is supported by the 3D3 Centre for Doctoral Training which is funded by the Arts and Humanities Council. Digitaltextileprintingblog.wordpress.com 3

4 Coating Experiments: A mix of urea, soda ash and manutex was applied to part of the substrate (cotton satin). The fabric was printed upon using a Mimaki wide format inkjet textile printer which uses reactive dyes. The uncoated side (left of picture) shows a lack of definition, print quality and colour take up in comparison to the coated side (right of picture). Pantone Colour Library: All 1137 Pantone Colours from Adobe Photoshop CC s Colour Library were printed onto 4 different substrates using a Mimaki TX with reactive dyes. Colour comparisons were made of the different substrates. The picture shows a detail of the wool print Tone of grey prints: The metrics behind the Pantone Colour Library were analysed and compiled into a colour reference book detailing alongside a visual reference printed onto paper, wool, linen, cotton and silk. The picture shows a selection of grey hues with great disparity between the appearance of each colour when printed across the five substrates (top down; paper, wool, linen, cotton, silk) 4

5 Memory effects, central tendency, serial dependency or just task bias? An investigation using illumination hue discrimination Stacey Aston1, Maria Olkkonen2,3, Anya Hurlbert1, 1Institute of Neuroscience, Newcastle University, UK 2Department of Psychology, Durham University, UK 3 Department of Psychology and Logopedics, Faculty of Medicine, University of Helsinki, Finland Holding perceptual estimates of surface and illumination colour in memory induces a bias toward the mean of recently viewed colours (Olkkonen et al. 2014, Aston et al. 2017). In the task, observers see a reference illumination and, after a two second delay, indicate if a test is bluer or yellower than the reference. There are three blocks of five references, some references appearing in multiple blocks, bluer than the average in one block but yellower in another. The hue value of the point of subjective equality (PSE) for a reference that is bluer than the mean block reference is yellower than the true colour (quantified by hue value). It is suggested that this effect is caused by central tendency or serial dependency, observers averaging over multiple reference presentations to minimise the uncertainty added by the task s memory requirement. We suggest that when the reference and test become indiscriminable, observers respond with the colour term that describes the appearance of the test, biasing the PSE in the opposing direction. We show that eliminating the naming element from the task (response not tied to bluer/yellower ) reduces bias magnitude. The remaining bias may still be due to categorisation effects if colours are encoded in memory by assignment to colour categories, although it might alternatively be a compensatory effect to account for deterioration of the reference hue in memory, pulling the PSE towards the observer s prior. It remains to be determined whether semantic categorisation effects influence the bias observed in similar experimental paradigms. Teaser (max. 50 words) Perceptual estimates of surface and illumination colours display a central tendency bias when held in memory. The effect is similar to those seen in studies of serial dependency. Here we show that the use of colour names in the task likely gives rise to the bias in perceptual estimates. 5

6 Dr Maria Olkkonen I received an M.A. in psychology (minor: philosophy) from the University of Helsinki in 2004, writing my master's thesis on the interaction between brightness and color information in the simultaneous contrast illusion. Working with Dr. Pentti Laurinen on my master's thesis made me realize what a powerful tool psychophysics is to study psychological processes and neural computation. After working in corporate research for a while at the Nokia Research Center, I decided to go back to academia and was offered a PhD studentship with Prof. Karl Gegenfurtner at the University of Giessen. During my time in the lab, I learned a lot about color constancy (and spray-painting fruit), and received my PhD in 2009 together with a swanky Doktorhut. To learn more about color and material constancy, I then moved to Philadelphia to work with Prof. David Brainard at UPenn. We did some nice experiments with a high-dynamic range display, which was a pain to calibrate but was well worth it. While in Philadelphia, I also worked with Prof. Sarah Allred at Rutgers on the relationship between color memory and perception, and finally did a two-year project in Prof. Russell Epstein's lab learning about fmri adaptation and MVPA methods. I've held an assistant professorship in Durham since September

7 Title: Differences in Color Naming between British and American English Speakers Conference: 13th AIC Congress 2017, Jeju, S. Korea Dimitris Mylomas In an ongoing web-based color naming experiment (available at: a large number of British (n=525) and American (n=525) participants with normal colour vision responded with names for 600 color stimuli. We examined differences in color naming between American and British English speakers and the agreement between their easy and hard to name colors as measured by the entropy of the distribution of the responses to each stimulus. British English speakers displayed a richer color vocabulary than American English speakers (number of distinct terms 2094 vs 1653), but the Americans named colors 10% faster than the British. A comparison of the centroids in CIE L*a*b*coordinates for the eleven basic color terms (BCTs) produced an excellent agreement (mean ΔE00=1.3) between the two groups of speakers, with the largest difference (ΔE00=2.7) for blue. Across stimuli, the degree of ambiguity in color naming was correlated between languages (R=0.55). British and American English speakers appear to be more united than divided by a common color language but differences do exist. 7

8 Title: Differences in Color Naming between British and American English Speakers Conference: 13th AIC Congress 2017, Jeju, S. Korea In an ongoing web-based color naming experiment (available at: a large number of British (n=525) and American (n=525) participants with normal colour vision responded with names for 600 color stimuli. We examined differences in color naming between American and British English speakers and the agreement between their easy and hard to name colors as measured by the entropy of the distribution of the responses to each stimulus. British English speakers displayed a richer color vocabulary than American English speakers (number of distinct terms 2094 vs 1653), but the Americans named colors 10% faster than the British. A comparison of the centroids in CIE L*a*b*coordinates for the eleven basic color terms (BCTs) produced an excellent agreement (mean ΔE00=1.3) between the two groups of speakers, with the largest difference (ΔE00=2.7) for blue. Across stimuli, the degree of ambiguity in color naming was correlated between languages (R=0.55). British and American English speakers appear to be more united than divided by a common color language but differences do exist. 8

9 AIer-effects from implied colours of natural objects Dr Robert Lee It is well known that after viewing a coloured stimulus the perception of subsequent stimuli is chromatically shifted in the opponent direction, because of biased output of early chromatic mechanisms. Recent studies show that known colours of familiar objects affect the perception of those objects, biasing the white-point in the direction opposite that of the memory colour. We investigated whether familiar object colours cause an after-effect by adapting observers to greyscale images of objects with diagnostic colour, before measuring the perceived white-point of simple geometric stimuli. In control measurements the adapting images were phase-scrambled. Despite the measurements being made with judgements of simple geometric stimuli, chromatic shifts were observed, relative to the control measurements. These shifts were consistent with adaptation to the colour implied by the objects. Our experiment was designed to eliminate potential response bias. These results could be interpreted as adaptation of colour-signalling mechanisms that are receiving top-down input, or in the context of colour constancy where the greyscale images are assumed to be the result of a prevailing illuminant with a colour complementary to the object colour. 9