This first edition of ISO/CIE 11664-4 cancels and replaces ISO 11664-4:2008 | CIE S 014-4:2007, of which it constitutes a minor revision. The document has been editorially revised as per current ISO and CIE rules and the references have been updated.

The document specifies a method of calculating the coordinates of the CIE 1976 L*a*b* colour space, including correlates of lightness, chroma and hue. It includes two methods for calculating Euclidean distances in this space to represent the perceived magnitude of colour differences.

The document is applicable to tristimulus values calculated using colour-matching functions of the CIE 1931 standard colorimetric system or the CIE 1964 standard colorimetric system. This document can be used for the specification of colour stimuli perceived as belonging to a reflecting or transmitting object, where a three-dimensional space more uniform than tristimulus space is required.

The document does not apply to colour stimuli perceived as belonging to an area that appears to be emitting light as a primary light source, or that appears to be specularly reflecting such light.

The document is applicable to self-luminous displays, such as cathode ray tubes, if they are being used to simulate reflecting or transmitting objects and if the stimuli are appropriately normalized.

Calculating the reverse transformation is shown in Annex A.

To enable people to perform visual tasks efficiently and accurately, especially during the night, adequate and appropriate lighting has to be provided. The degree of visibility and comfort required in a wide range of outdoor work places is governed by the type and duration of activity.

The standard specifies the lighting requirements that will contribute to the visual needs for safety and security within outdoor work places.

This paper reports a procedure of making better urethane skin samples which have spectral reflectance factors close to real human skin color data by using a method of computer color matching (CCM).

A CCM system based upon absorber and scatter theory by Kubelka Munk and relations equation by Saunderson were used.

We prepared a pigments database which accumulated each pigment’s spectral reflectance factor and Kubelka-Munk’s absorption and scattering coefficient.

By using the CCM system and the pigment database, we found the optimal pigment blending ratios and made the new urethane sample’s data, which produced the almost same spectral reflectance factors as real skin, significantly better than previous urethane samples in our research.

In this study, the visibility of the phantom array effect
under indirect viewing office lighting conditions was tested to verify whether it can cause a
problem when making saccades across words during reading.

Results show that, under a very
critical condition of a white target on a black surface, the phantom array effect is easily
perceived, especially at the intermediate frequency of 600 Hz.

But under the normal reading
condition of a black target on a white surface, the phantom array effect becomes very difficult
to detect.

Temporal light modulation, (TLM) of lighting systems is known to affect human visual
perception, neurobiology, and performance.

This experiment measured Stroop cognitive
performance, reading performance, eye movements, discomfort, and phantom array
perception during exposure to each of nine TLM conditions chosen to contrast conditions
varying in TLM frequency, modulation depth, or duty cycle and based on predictions drawn
from the IEEE S1789-2015 recommendations.

Data from 50 adult participants aged 18-65
revealed small effects mostly in predicted directions.

The results support the recommendation
that lower modulation depths are preferable over higher, and add to our knowledge by
showing that duty cycle could also influence outcomes and that the phantom array can be
detected under photopic conditions.

This underlies the importance of taking a lighting
systems approach to studying TLM and considering a range of effects.

Future research
should increase statistical power by increasing task difficulty, and duration of exposure.

More
naturalistic viewing conditions, such as a greater range of eye and head motion, would
improve the generalizability of the work.

This study aimed to investigate colour appearance in virtual reality (VR).

A total of 35 test
colours were visually assessed in a VR space by 16 observers in terms of lightness,
colourfulness and hue quadrature.

The experimental results show high correlation between
perceived colour appearance and predicted values by CIECAM02, with a correlation coefficient
of 0.96 between perceived lightness and CIECAM02 J, 0.99 between perceived hue quadrature
and CIECAM02 H, and 0.88 between perceived colourfulness and CIECAM02 M.

Intense blue spectral light components pose a short-term risk to the retina, called blue light
hazard (BLH).

For this photochemically-induced retinal injury spectral weighting functions and
applicable limit values are established.

However, scientific evidence about blue light as a
long-term risk factor promoting age-related macular degeneration (AMD) is less descriptive.

Some studies indicate that a spectral weighting function seems to be similar to the function
used for BLH.

However, there are some scientific papers reporting good therapeutic results in
patients with AMD by the use of a therapy called “photobiomodulation”.

This indicates that red
and near infrared (NIR) spectral components could be beneficial by counteracting blue light
induced AMD.

In order to describe the balance between the risk potential of blue and the
protection potential of red/NIR spectral components an “AMD protection index” is proposed
and is applied to various spectra of light sources including LEDs for comparison.

Light exposure elicits numerous effects on human physiology and behaviour, such as better
alertness and mood.

Here we investigated the effects of natural eye light exposure before
awakening on sleep quality and morning alertness and mood.

16 subjects from 4 dormitories in
the same class of Tsinghua University were selected to conduct a 30-day field experiment in
summer.

Because of the different distance from the window and the wall shelter, the distribution
of natural light in the 4 beds of dormitory in the morning is also different.

The natural eye light
exposure before waking up was obtained by a wireless probe, which could record illumination
in real-time.

The physiological and psychological indicators such as sleep quality at night,
alertness and mood after waking up were obtained by questionnaires and sleep monitoring band.

The results showed that the more the LEA before waking up, the better alertness and mood
after waking up.

But no significant correlation was found between sleep quality and LEA.

Substantial efforts have been made to investigate how light source color rendition affects color
preference.

It has been widely agreed that a source with a high color fidelity score may not
result in higher color preference, as a higher saturation is generally preferred.

Two
psychophysical experiments were designed to investigate the color preference of an artwork
under nine nearly metameric stimuli with a gamut area (i.e., IES Rg) between 99 and 124 across
a wide range of illuminance levels (i.e., from 20 to 15000 lx), which was never carefully studied
before.

These different Rg values of the stimuli were designed to be produced by systematic
changes in IES TM-30 red and green chroma shifts.

The findings revealed that the light level
had a significant impact on color appearance and color preference, with a stimulus having a
larger gamut area being preferred under a lower illuminance level.

It suggested that light level
should be considered when specifying light source color rendition.

Due to their potential use as an internal reference, memory colours have proven to provide an
excellent conceptional approach for the colour rendition evaluation of white light sources in
terms of predicting visual appreciation.

However, there are still some major drawbacks that can
be identified in the principal design of existing memory-based or memory-related colour quality
metrics.

For this reason, a new experiment was devised trying to overcome the shortcomings
of these previous approaches.

Based on the experimental output, the main goal of the current
study consequently was to derive an improved version of a memory-based colour quality metric,
which provides a superior tool for developers and manufacturers that can be used for the
optimization of state-of-the-art lighting solutions in cases where visual appreciation and high
user acceptability are more important than colour fidelity.

An experiment is reported showing the dependency of sparkle and glare perception on
luminance and area of a light source.

The experimental conditions are chosen such that the
results can be applied to design aesthetically pleasant LED sources.

Similar to results of
previous studies, probabilities of sparkle and glare perception are conveniently expressed in
the luminance-area parameter space.

In recent years a Predictable Quantum Efficient Detector (PQED) has been developed by a joint
European effort in the framework of the EUROMET iMERA+/EMRP programs.

The PQED
consists of two custom-made induced junction Silicon photodiodes in a wedge trap
configuration.

The most notable property of this type of detector is that its external quantum
efficiency (EQE) value in the spectral range from 400nm to 850nm is dependent only on
fundamental constants.

The PQED is therefore potentially an ideal candidate for a new primary
standard for optical radiometry in the visible range.

A considerable effort has been spent to
validate the absolute value of the PQED spectral responsivity against the current standard for
optical radiometry, the cryogenic radiometer, with standard uncertainty below 100 ppm.

The
aim of this work is to investigate the PQED long term temporal stability when operated at room
temperature.

Parking lot lighting should meet multiple objectives.

One important design objective is that
parking lot lighting should provide a sense of personal safety and security.

This objective has
been the focus of studies from the Lighting Research Center since the 1990s, which involved
research on lighting characteristics such as the average illuminance, the spectral power
distribution of the light source, and the uniformity of illumination across the parking lot
surface.

Building upon this body of research, a recent study is described in which the
interactions among these factors, not only their isolated impacts, on subjective perceptions of
safety and security are assessed.

The research efforts described here demonstrate how light
level, spectrum and uniformity combine to affect perceptions of safety in parking lot users.

Importantly, specifications of lighting based on these criteria would permit substantial
reductions in energy use and light pollution in outdoor lighting while meeting users' needs.

: Safety and Security, Visual Performance, Exterior Lighting

The goal of the study was to investigate the effects of human centric lighting on the users via
both objective measurements and subjective questionnaires in a real working environment with
the participation of industrial employees.

During the experimental sessions, heartrate of the
participants had been monitored and the questionnaires periodically had to be filled out,
assessing the participants’ experiences about the experimental lighting.

The results of the
statistical analyses of the questionnaires clearly show a connection between circadian effects
of the human centric lighting’s continuously changing light settings and the participants’
subjective feeling of alertness and their preferences.

The effect of lighting had been proven
using objective measurements besides the questionnaires.

A significant moderate correlation
between the circadian effect and the heartrate changes had been shown.

The moderate strength
can be acknowledged to other factors which influence the heartrate.

Hunt Effect is a phenomenon in which object colours at low light levels are perceived less
saturated compared to that at higher light levels.

If this effect is effective at normal indoor
lighting levels, increasing the chroma saturation level at indoor lighting to some extent would
make colour appearance of objects closer to that under outside daylight, thus bring higher
fidelity of colours.

To verify whether the Hunt Effect is effective at normal indoor lighting,
vision experiments were conducted using a spectrally tuneable lighting facility simulating a
real size interior room.

Observers viewed real fruits and vegetables and their skin tones under
different chroma levels in red-green direction at illuminance levels of 100 lx and 1000 lx, and
evaluated naturalness of these targets.

The results showed significant differences between
100 lx and 1000 lx; subjects perceived objects as most natural at less chroma level at 1000 lx
than at 100 lx.

The studies on visibility of traffic sign, yellow raincoat and yellow helmet on an experimental
road for dynamic road-lighting in a foggy environment were performed.

We used an image
luminance measuring device to measure the luminance images.

The analysis of the
experimental results were obtained by the defined contrast ratio and the threshold of fog index.

The visibility of objects in HPS and LED lighting in the foggy environment can be analysed.

: Traffic sign, Fog, Contrast Ratio, Dynamic road-lighting

Glare is a key factor that influencing the visual performance in light conditions of airplane
cockpit, and intensity and layout of glare sources in cockpit are extraordinarily complex.

This
study investigates the relationship between complex glare sources and discomfort glare
evaluations of luminous environment in airplane cockpit.

Different glare indices are proposed
to predict the level of discomfort glare in the cockpit environment with non-uniform glare sources
and irregular shape glare sources.

The result shows the DGP can predict the visual comfort
evaluation better than DGI and UGR in complex luminous environments.

Our previous experiment showed that the Hunt Effect was effective at normal indoor lighting
levels.

The purpose of this study is to quantify the level of perceived chroma increase by the
Hunt Effect.

Two identical colour patches were placed on the left and the right side of the booth.

The left side of the booth was illuminated at 1000 lx with a broadband spectrum and the right
side was illuminated at 100 lx or 300 lx with chroma-increasing lights with different chroma
increase levels.

Subjects viewed each side of the booth with each eye (haploscopic viewing
condition) and were asked to select a light of the right side that matched the colour of the right-
side target closest to the left one.

Results showed that increased chroma by 15 to 18 in ?C*ab
were needed for the right side to match perceived chroma.

The chroma increase was smaller
at 300 lx.

In recent years, both the quality of the light environment and the reduction of lighting energy
are required in offices.

To realize these requirements, it is effective to reduce the illumination
of background area where occupants are absent while keeping the brightness of the task area
where occupants are present.

In this study, we conducted a subjective evaluation of spatial
brightness in a non-uniform lighting environment based on the European standard and in a
uniform lighting environment.

In the experiment, the satisfaction of the whole lighting
environment was taken as a superordinate concept, and the absolute level of brightness,
visibility, the appropriateness of brightness, and non-uniformity were evaluated as factors
explaining the satisfaction.

As a result, in the non-uniform lighting environment in conformity of
the European standard, while visibility and absolute brightness levels around desktops were
highly evaluated, the level of satisfaction with light environment was low.

To identify lighting requirements for ADB systems to help drivers detect off-axis potential
hazards when oncoming headlight glare exists in a night-time roadway, we conducted target
detection tests under various experimental conditions in a laboratory.

In the experiment, we
used a simulated ADB system which can illuminate only targets locally and therefore increase
the luminance contrasts of the targets.

The experimental results suggest that the ADB system
is more efficient lighting methods than conventional forward lighting systems which illuminate
the entire visual field to increase drivers’ adaptation luminance levels.

Based on the detection
rates, we also determined requirements for threshold luminance contrast for targets with
oncoming headlight glare.

has been conceived to address the analysis of the current nocturnal landscape image, carried
out through both qualitative and quantitative analysis.

In the paper results obtained from the
application of the method to a case study are presented.

This first conference focused on Smart Lighting, an area that is expected to bring significant energy savings and many other benefits. The conference provided scientific and technical inputs in order to progress development of technologies with confidence in regards to lighting quality, comfort, and safety.

The Proceedings of this Conference consist of 1215 pages including 158 papers of oral and poster presentations.

• the object itself and its optical characteristics;
• the position, size, shape and spectrum of the light source;
• the nature of the visual field surrounding the object;
• the observer’s visual system with its amazing complexity.

Research areas have been formed which are devoted to the four visual attributes: colour, gloss, texture and translucency. The development of new visual appearance effects, such as goniochromatism and graininess, have required progress and evolution in the quantification of visual appearance and corresponding measurement setups. The outcome of research in this area is significant for industrial sectors where the measurement of visual appearance is important and for manufacturers of measurement equipment. During this joint symposium of CIE Divisions 1 and 2 presentations were given on:

• the state of the art in our understanding of the perception of the visual attributes, such as colour, texture, translucency and gloss;
• the latest achievements in the fields of novel measurement methodologies such as BRDF, BTDF, BSSRDF and others;
• possible applications of visual appearance knowledge and novel measurement methodologies for the design and characterization of modern optical surfaces.

The document does not give complete information for particular lighting applications, or for the quantitative prediction of IIL responses.

The document is not intended for colorimetric contexts, nor does it address health or safety issues such as those resulting from light treatment, flicker or photobiological safety and only relates to retinal photoreception.

Tables of the data of the action spectra of the five photoreceptor types defined in this document are made electronically available for purchasers of this publication via a respective download link.

This International Standard has been approved by the CIE National Committees. The document is readily available from the CIE Webshop or from the National Committees of the CIE.