 |
MEETINGS FOR 2009-2010
Wednesday 4 November 2009 |
Palmer Award Presentations
An Educational Exercise
City
University, London
Holders of the awards made for 2009 make presentations to describe
their work and a panel of
experts provide feedback
on these presentations
which is aimed to help the awardees. The ability to
describe accurately their work
in a lively and
interesting way is seen as a vital talent for the careers that
the awardees are likely to persue.
This educational role is
seen to be at the heart of the Colour Group's objectives.
Time:
14.00 hrs
Place:
Teaching Room AG22, College Building, City University (College Building is in St John's Street,
enter under the clock)
Programme:
14:00 Introduction
14:10 Sara Moorhouse Spatial colour effects across
three-dimensional form:
from the tilt
effect to the whole form illusion
14:35 Yashu Ling
The interaction
of colour and texture in an object
classification task
15:00 Shuo-Ting Wei
Quantification of
the relations between juice colour and
consumer
expectations
15:25 Halstead-Granville
Tea
15:45 Naveen K
Challa L-
and M-cone input to human ERGs as a function of
retinal
eccentricity
16:00 Vanda A Nemes
A behavioural
investigation of human visual short term
colour memory
16:25 Chenyang
Fu Changes in colour perception across the
life span (presented
by Kaida Xiao)
16:50 Prize
presentation
17:00 End
Abstracts
Spatial colour
effects across three-dimensional form: from the tilt effect to the
whole form illusion
Sara Moorhouse
Art and Design, University of Wales Institute, Cardiff
This doctoral research examines and analyses the spatial activity
created by colour combinations, drawn from landscape, when applied to
three-dimensional form. Colours perform spatially upon a
two-dimensional surface in a multitude of ways, which may be
significantly affected by the formal structure of three-dimensional
artworks.
My research has shown that bands of colour arranged upon the
three-dimensional bowl, display spatial manoeuvres that are not found
within identical alignments of hues upon a two-dimensional surface. A
key finding to date is the ‘tilt effect’, an illusion that bends form
and creates tension between inner and outer surfaces. This phenomenon
is so resolute and compelling, that not only can a dual tilt appear,
but further unexpected spatial events can be perceived.
Such effects, once determined, may be used as an abstract language
across the mediums of painting and ceramics. Through manipulation
of hue, the colours and essence of landscape can be represented;
through the appearance of illusion on form, landscape can be further
realized, to suggest its volume, movement, contours and scale.
The paper will describe briefly the methods used for the research and
discuss and illustrate key findings and exciting visual phenomena
uncovered to date.
The interaction of
colour and texture in an object classification task
Yashu Ling
Institute of Neuroscience, Newcastle University
Many natural objects are characterised not only by shape and mean
colour, but also by their particular chromatic textures: the speckled
red of a strawberry is distinctively different from the streaky red of
an apple. While the roles of colour and shape have been well
explored in object recognition, chromatic texture has not. Here we
study the roles of mean colour and texture – and their interaction --
in an object classification task using familiar objects.
Images of natural objects were captured using a tristimulus-calibrated
digital camera under controlled illumination. Reference surface patches
were taken from different locations on single objects, and then
manipulated by changing either their original texture or colour (e.g.
combining banana texture with carrot colour). Stimuli were presented on
a calibrated CRT monitor.
Observers performed a three-way speeded classification task for 3
stimulus sets: uniform colour patches (red, green or blue), whole
natural object images (shape cue intact) and natural surface patches
(‘congruent’, i.e., reference patches, and ‘incongruent’, i.e.,
manipulated patches). For the latter two sets, 3 groups were formed
from combinations of 7 objects (example classification: potato, lime,
or carrot). The task was performed at 2 different presentation
times (40 ms and 250 ms).
Observers were able to perform the task, even for incongruent patches.
Classification performance (reaction time and accuracy) for whole
object images was effectively the same as for uniform colour, at both
presentation times. Classifications for incongruent patches were slower
than for congruent patches, most pronouncedly at 40ms. Incongruent
textures slowed down classification by colour more than incongruent
colours impeded classification by texture, only at the shortest
presentation.
The results strongly suggest that texture and colour interact in object
recognition and, at least for this task, texture plays a more dominant
role than mean colour in object classification.
Quantification of
the relations between juice colour and consumer expectations
Shuo-Ting Wei
Department of Colour Science, University of Leeds
The paper describes methods for defining an ideal orange juice by the
consumers’ acceptability judgements and for modelling the consumers’
tastes according to juice colours.
In this study, the orange juice in the frequently used clear bottle was
used. The orange juice was used to represent a wide range of food juice
range. The results showed that the colour of the juice not only plays a
significant role of package appearance, but also directly affects
consumers’ expectation of taste. An ideal orange juice colour in terms
of CIELAB L*, a* and b* values was defined. In addition, the
fine-grained influence of juice colours on five basic taste categories:
sour, sweet, bitter, flavour strength and freshness was also revealed.
The resulting models provide effective tools to “soft-evaluate”
packaging products before launching. The information is vital for
supporting the sale of the products. The models developed also provide
a bridge between the colour scientists, designers and marketing
experts. Being able to communicate with researchers from different
colour communities around the globe is of great importance to my
academic development. The presentation is important as a continuation
of my earlier PhD results presented in AIC08, Stockholm.
L- and M-cone
input to human ERGs as a function of retinal eccentricity
N. K.Challa1, D. McKeefry1,
N.R.A. Parry2, J. Kremers3,
I.J. Murray4 & A.
Thanasis4
1 Department of Optometry and Vision Science, Bradford
University, UK.
2 Visual Sciences Centre, Manchester Royal Eye Hospital, Oxford Rd,
Manchester, UK.
3 Department of Ophthalmology, University Hospital Erlangen, Erlangen,
Germany.
4 Faculty of Life Sciences, University of Manchester, Manchester, UK.
We recorded L- and M-cone isolating ERGs from human subjects using a
silent substitution technique at temporal rates of 12Hz and 30Hz. These
frequencies isolate the activity of cone-opponent and non-opponent
post-receptoral mechanisms, respectively. ERGs were obtained using a
sequence of stimuli with different spatial configurations comprising;
i) circular stimuli of different sizes which increased in 10 steps up
to 70° diameter, or ii) annular stimuli with a 70° outer diameter but
with different sized central ablations from 10 up to 60. L- and
M-cone isolating ERGs were obtained from five colour normal subjects
using a DTL fibre electrode. Fourier analysis of the ERGs was performed
and we measured the amplitude of the first harmonic of the response.
For 30Hz ERGs the L:M cone response amplitude ratio (L:MERG) varied
across observers and as a function of retinal eccentricity. For 12 Hz
the L:MERG ratio was close to unity for all observers and remained
constant as a function of retinal eccentricity. The maintenance of this
balanced ratio points to the existence of cone selective input in the
peripheral human retina for the L-M cone opponent mechanism.
A behavioural
investigation of human visual short term colour memory
Nemes VA1, Parry NRA2,
McKeefry DJ1
1 Bradford School of Optometry and Vision Science,
University of Bradford, UK
2 Vision Science Centre, Manchester Royal Eye Hospital, Oxford Rd, UK
We examined visual short term memory (VSTM) for colour using a
delayed-match-to-sample paradigm by measuring the effects of increasing
inter-stimulus intervals (ISIs), varying between 0 and 10 seconds, on
the ability of 2 colour normal human observers to make colour matches
between a reference and subsequently presented test stimulus. The
coloured stimuli used were defined by different chromatic axes on the
isoluminant plane of DKL colour space. In preliminary experiments we
used a hue naming procedure to identify 4 unique hues and 4 other hues
termed ‘non-unique’. We also used 4 colours which were located on the
cardinal axes and isolated the activity of the cone-opponent
mechanisms. These 12 key colour stimuli served as reference hues in the
colour memory experiments. Our results showed that there was
deterioration in the ability of the observers to make colour matches
with increasing ISIs and this decay was similar for all colour stimuli.
However, differences in hue between matches made for unique hues at the
longest ISIs were smaller than those obtained for matches made between
cone-opponent stimuli. This stability in terms of retention for unique
hues in VSTM may point to a special status for phenomenologically
important hues in colour memory.
Changes in colour
perception across the life span
Chenyang Fu
School of Psychology, University of Liverpool
We assessed chromatic sensitivity along the protan, the deutan, and the
tritan line (Cambridge Colour Test, CRS Ltd.), the loci of the unique
hues (red, green, yellow, blue) and the achromatic locus (neutral grey)
for a very large sample (n=185) of colour-normal observers ranging from
18 to 75 years of age. Visual judgements were obtained under normal
viewing conditions using broad-band self-luminous stimuli (CRT) under
controlled adaptation conditions. We found that Trivector
discrimination thresholds increased as a function of age along the
protan, the deutan, and the tritan axis (with coefficient of
determination of R2 > 0.1), with the largest increase being present
along the tritan line, which is consistent with the known age-related
changes in the lens. We find less pronounced shifts in unique hue
settings. Unique red and unique yellow settings do not change with age.
Unique blue shifts towards green and unique green shift towards yellow;
however, the coefficient of determination is very small in both cases
(R2 <0.1). Similarly, the locus of neutral grey is not affected by
age (R2 <0.1). We conclude that the chromatic sensitivity
deteriorates significantly with age, whereas the appearance of unique
hues and neutral grey is much less affected remaining almost constant
despite the known changes in the ocular media. Our study provides
useful normative data both for sensitivity and appearance changes
throughout the life span.
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