SIST-TP CEN/TR 16791:2017
(Main)Quantifying irradiance for eye-mediated non-image forming effects of light in humans
Quantifying irradiance for eye-mediated non-image forming effects of light in humans
This European Standard defines metrics that can be used to evaluate and compare lighting conditions with respect to their potential to achieve non-image forming, eye-mediated effects of light in human beings. This European Standard also provides information for application in lighting practice with relevance for both the public and private domain. However, the scientific knowledge is not yet mature enough to craft specifications for lighting conditions that can achieve specific non-image forming effects in humans. Moreover, this European Standard does not give information on lighting practices related to shift work.
This European Standard does not address health safety issues such as resulting from flicker, photobiological safety or the effects of non-visible optical radiation (ultraviolet and infrared radiation).
Bewertung von Strahlung für nichtvisuelle Wirkungen von Licht bei Aufnahme über die Augen
Diese Norm definiert Maße, die zur Überprüfung und zum Vergleich von Beleuchtungsbedingungen verwendet werden können, hinsichtlich ihres Potentials, nicht bildgebende, durch das Auge übermittelte Einflüsse des Lichts auf den Menschen zu bewirken. Diese Norm stellt außerdem Informationen zur Anwendung in der Beleuchtungspraxis bereit, die sowohl für den öffentlichen als auch den privaten Bereich relevant sind. Allerdings ist der wissenschaftliche Kenntnisstand noch nicht ausreichend ausgereift, um Festlegungen für Beleuchtungsbedingungen zu erstellen, die spezielle, nicht bildgebende Einflüsse auf den Menschen haben. Außerdem liefert diese Norm keine Beleuchtungspraktiken im Zusammenhang mit Schichtarbeit.
Diese Norm befasst sich nicht mit Gesundheitsschutzbelangen, wie sie z. B. durch Flimmern, photobiologische Sicherheit oder die Einflüsse nicht sichtbarer, optischer Strahlung (Ultraviolett- und Infrarotstrahlung) entstehen.
Quantification de l'éclairement énergétique pour les effets non formateurs d'image de la lumière transmise par le biais des yeux chez l'homme
La présente norme définit un système de mesure pouvant être utilisé pour évaluer et comparer les conditions d'éclairage en ce qui concerne leur potentiel d'engendrer des effets non formateurs d'image par le biais des yeux chez les êtres humains. La présente norme fournit également des informations pour une application dans les pratiques en matière d'éclairage, aussi bien dans le domaine public que privé. Toutefois, les connaissances scientifiques ne sont pas encore suffisamment affinées pour permettre l’élaboration de spécifications relatives aux conditions d'éclairage pouvant engendrer des effets spécifiques non formateurs d'image chez les êtres humains. Par ailleurs, la présente norme ne fournit pas d'informations sur les pratiques d'éclairage en relation avec le travail posté.
La présente norme ne traite pas des problèmes de santé et de sécurité tels que ceux résultant d'un papillotement, de la sécurité photobiologique ou des effets des rayonnements optiques non visibles (rayonnements ultraviolet et infrarouge).
Vrednotenje sevanja za ne-slikovne učinke svetlobe pri gledanju
Ta evropski standard opredeljuje merila, ki se lahko uporabljajo za vrednotenje in primerjavo svetlobnih pogojev glede na njihovo možnost za ustvarjanje ne-slikovnih učinkov pri gledanju. Ta evropski standard podaja tudi informacije, ki se uporabljajo pri praksah osvetlitve tako v javni kot v zasebni sferi. Vendar znanost še ni dovolj razvita, da bi se oblikovale specifikacije za svetlobne pogoje, ki lahko ustvarijo določene ne-slikovne učinke pri gledanju. Poleg tega ta evropski standard ne podaja informacij glede praks osvetlitve, povezanih z izmenskim delom.
Ta evropski standard ne zajema zdravstvenih težav, ki so na primer posledica utripanja, fotobiološke varnosti ali vplivov nevidnega optičnega sevanja (ultravijolično in infrardeče sevanje).
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
SIST-TP CEN/TR 16791:2017
01-december-2017
9UHGQRWHQMHVHYDQMD]DQHVOLNRYQHXþLQNHVYHWOREHSULJOHGDQMX
Quantifying irradiance for eye-mediated non-image forming effects of light in humans
Bewertung von Strahlung für nichtvisuelle Wirkungen von Licht bei Aufnahme über die
Augen
Quantification de l'éclairement énergétique pour les effets non formateurs d'image de la
lumière transmise par le biais des yeux chez l'homme
Ta slovenski standard je istoveten z: CEN/TR 16791:2017
ICS:
17.180.20 Barve in merjenje svetlobe Colours and measurement of
light
SIST-TP CEN/TR 16791:2017 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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CEN/TR 16791
TECHNICAL REPORT
RAPPORT TECHNIQUE
August 2017
TECHNISCHER BERICHT
ICS 17.180.20
English Version
Quantifying irradiance for eye-mediated non-image-
forming effects of light in humans
Quantification de l'éclairement énergétique pour les Bewertung von Strahlung für nichtvisuelle Wirkungen
effets non formateurs d'image de la lumière transmise von Licht bei Aufnahme über die Augen
par le biais des yeux chez l'homme
This Technical Report was approved by CEN on 2 July 2017. It has been drawn up by the Technical Committee CEN/TC 169.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,
Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Turkey and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2017 CEN All rights of exploitation in any form and by any means reserved Ref. No. CEN/TR 16791:2017 E
worldwide for CEN national Members.
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Contents Page
European foreword . 3
Introduction . 4
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 5
4 Non-visual effects of light . 10
4.1 General . 10
4.2 Characterization of light regarding non-image-forming effects . 11
4.2.1 Measurement of spectral power distribution . 11
4.2.2 Determination of each of the photoreceptor inputs . 12
4.3 Pre-receptoral filtering considerations . 15
4.3.1 General . 15
4.3.2 Definitions for age-corrected quantities . 16
Annex A (informative) Examples of use . 19
A.1 Quantifying stimulus to photoreceptors by illuminants . 19
A.2 Discussion on cumulated photoreceptor input for non-image-forming effects . 22
Bibliography . 23
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European foreword
This document (CEN/TR 16791:2017) has been prepared by Technical Committee CEN/TC 169 “Light
and lighting”, the secretariat of which is held by DIN.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent
rights.
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Introduction
There is strong scientific evidence that light is not only essential for vision but also elicits important
biological, non-image-forming effects that are highly relevant for human performance and well-being.
The non-image-forming effects can be either eye or skin mediated (e.g. vitamin D production, skin
cancer or solar dermatitis). This document focuses on the eye-mediated non-image-forming effects.
Depending on time of light exposure, spectral power distribution, duration of exposure, and individual
parameters like circadian phase, light history, and others, light can cause suppression of the nocturnal
release of melatonin, increase heart rate as well as alertness and affect thermoregulation [17], or the
electroencephalogram spectrum. Light is the main synchroniser of the human biological clock. It can
shift the phase of the circadian system and determines the timing of sleep/wake cycle. In a proportion
of patients, light exposure can alleviate seasonal and non-seasonal depression and improve quality of
life [1]. Upon light exposure, fast responses in the range of seconds were seen in the pupillary reflex or
in brain activity.
The current lighting practice and the tendency for energy saving, e.g. European Regulations 244/2009
and 859/2009 as well as 245/2009 and 347/2010 tend to reduce indoor illumination levels. This can
create lighting conditions that are sub-optimal for human well-being, health and functioning.
The above mentioned biological effects of light are elicited by stimulation of ocular photoreceptors. The
receptors for vision, the rods and cones, are relatively well understood and characterized by standards
such as CIE S 017. Although melanopsin containing retinal ganglion cells (intrinsically photosensitive
Retinal Ganglion Cells, ipRGCs) play an important role in the non-image-forming effects of light, this
photoreceptor is not yet included in existing lighting standards and recommendations. Therefore, a
description of optical radiation solely according to the photopic action spectrum is not sufficient. The
actual biological effect to ocular exposure to light will depend on the relative response of all
photoreceptors and there is good evidence for synergistic responses between the receptors. For a
deeper understanding of how a stimulation of the photoreceptors leads to a desirable or undesirable
biological effect, light will be characterized in a way to quantify the input to each of the five known
photoreceptors.
It is also important to recognize the importance of darkness, and the daily pattern of light and dark,
particularly around and during periods of sleep. Additionally, certain changes to the balance of the
spectrum of light at different times of day might be helpful in promoting circadian rhythms [18], but
further evidence would be needed to support this as a general principle. Analysing the involvement of
different photoreceptors would be crucial to understand how such outcomes with impact on human
health are provoked.
The biological non-visual effects of light have a direct impact on human performance and well-being
with large implications for architecture, indoor design, and lighting as well as for social- and work-
schedules. The integration of these effects in lighting applications and designs requires new metrics to
quantify light.
This report contains input of experts that, at the time of writing, also have contributed to the Draft
International Standard in preparation by CIE JTC 9 "CIE system for metrology of ipRGC influenced light
response". This Technical Report is entirely informative in nature and, unlike CIE JTC 9, does not
address field of view aspects. Consequently, insights, terminology, tables (on spectral sensitivity and
age correction) and symbols used in this report may be outdated after publication of the new CIE
standard.
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1 Scope
This Technical Report proposes metrics that can be used to evaluate and compare lighting conditions
with respect to their potential to achieve non-image-forming, eye-mediated effects of light in human
beings. This document applies to visible optic radiation in the wavelength range from 380 nm to
780 nm.
This Technical Report does not give information for particular lighting applications.
This Technical Report does not address health safety issues such as resulting from flicker,
photobiological safety or the effects of non-visible optical radiation (ultraviolet and infrared radiation).
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any amendments) applies.
EN 12665, Light and lighting - Basic terms and criteria for specifying lighting requirements
CIE S 017/E:2011, ILV: International Lighting Vocabulary
3 Terms and definitions
For the purposes of this document, the terms and definitions given in CIE S 017/E:2011, EN 12665 and
the following apply.
NOTE The differences for definitions of spectrally-weighted quantities that follow the SI convention are given
where applicable.
3.1
α-opic
relating to the characteristics in non-visual photometry of the specified human photoreceptor and its
opsin-based photopigment, denoted by α
Note 1 to entry: The symbol α represents one of the five photopigments. α can take one of five values, set out in
Table 1. See 3.1.1 to 3.1.5.
Note 2 to entry: Based on [13].
3.1.1
S-photopic
relating to S-photopsin, the human S-cone photopigment (α = “sp”)
Note 1 to entry: S-photopsin is sometimes denoted as cyanopsin. In this report the term S-photopic is used to
differ from other publications that are using slightly different sensitivity functions and denoting this sensitivity by
the word cyanopic.
Note 2 to entry: The maximum of S-cone sensitivity is in the blue spectral region at 445 nm. S denotes
maximum sensitivity at short wavelengths.
Note 3 to entry: The function for S-photopic sensitivity is based on the 10° cone fundamentals in CIE 170–
1:2006.
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3.1.2
M-photopic
relating to M-photopsin, the human M-cone photopigment (α = “mp”)
Note 1 to entry: M-photopsin is sometimes denoted as chloropsin. In this report the term M-photopic is used to
differ from other publications that are using slightly different sensitivity functions and denoting this sensitivity by
the word chloropic.
Note 2 to entry: The maximum of M-cone sensitivity is in the green spectral region at 540 nm. M denotes
maximum sensitivity at medium wavelengths.
Note 3 to entry: The function for M-photopic sensitivity is based on the 10° cone fundamentals in CIE 170–
1:2006.
3.1.3
L-photopic
relating to L-photopsin, the human L-cone photopigment (α = “lp”)
Note 1 to entry: L-photopsin is sometimes denoted as erythropsin. In this report the term L-photopic is used to
differ from other publications that are using slightly different sensitivity functions and denoting this sensitivity by
the word erythropic.
Note 2 to entry: The maximum of L-cone sensitivity is in the yellow-red spectral region at 570 nm. L denotes
maximum sensitivity at long wavelengths.
Note 3 to entry: The function for L-photopic sensitivity is based on the 10° cone fundamentals in CIE 170–
1:2006.
3.1.4
scotopic
relating to rhodopsin, the human rod photopigment (α = “rod”)
Note 1 to entry: Scotopic is sometimes denoted as rhodopic. Please note that in [13] the spectral sensitivity for
rods is denoted as “rhodopic”, but the values given there are not equivalent to CIE definitions for scotopic vision.
This is the reason for use of “scotopic” in this document.
Note 2 to entry: The sensitivity function used in this technical report as scotopic is identical to V’(λ), the
sensitivity function of the rods as defined in CIE S010:2005 (ISO 23539).
3.1.5
melanopic
relating to melanopsin, the photopigment contained in human ipRGC (α = “mel”)
Note 1 to entry: The term usually indicates the photoreception of the ipRGCs that is driven by the photopigment
melanopsin. The term “melanopic effects” can be used to denote non-visual effects that are mediated by the
intrinsic photosensitivity of melanopsin containing ipRGCs. Even though melanopsin containing retinal ganglion
cells are present in many different species, the data published here is only valid for humans mainly because of the
inherent ocular transmittance data.
Note 2 to entry: The data used in this report for melanopic sensitivity is based on [13], but the sensitivity
function has been normalized to a maximum that is equal to 1 at 490 nm.
Note 3 to entry: The function for melanopic sensitivity is including the pre-receptoral filtering by the human
ocular system for a reference observer at an age of 32 years.
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3.2
α-opic spectral efficiency (of monochromatic radiation of wavelength λ)
(λ)
sα
spectral sensitivity of one of the five human α-opic photopigments to irradiance incident at the eye’s
outer surface of a standard observer, normalized to the maximum of 1
Note 1 to entry: The unit of the α-opic spectral efficiency is 1.
Note 2 to entry: The spectral efficiency function s (λ) is representing the relative spectral effectiveness of
α
optical radiation to stimulate the α-opic photopigment at wavelength λ in relation to its maximum effectiveness at
wavelength λ which is defined as 1 for each of the five α-opic photopigments. Equivalent terms for spectral
α,max
efficiency function are “action spectrum” or “spectral weighting function”.
Note 3 to entry: The effectiveness of polychromatic radiation to stimulate the α-opic photopigment is assessed
by spectrally weighting the spectral power distribution of the polychromatic radiation by the spectral efficiency
function as described in 3.3.
3.3
α-opic radiant quantity
spectral radiant quantity weighted with the α-opic spectral efficiency defined by the formula
XX= ∫ λ sdλλ (1)
( ) ( )
e,α e,λ α
where
is the spectral radiant quantity;
X λ
( )
e,λ
is the α-opic spectral efficiency (of monochromatic radiation of wavelength λ) as defined in
s λ
( )
α
4.2.2, Table 2.
Note 1 to entry: In general X (λ) is a spectral radiometric quantity. E.g. when X (λ) is the spectral radiant
e,λ e,λ
flux (Φ (λ)), X represents the α-opic radiant flux which may be denoted by Φ . In this case the unit for Φ
e,λ e,α e,α e,α
would be W.
Note 2 to entry: In a second example X (λ) could be the spectral radiance. In this case X represents the α-
e,λ e,α
-1
opic radiance which may be denoted by L with units W·sr .
e,α
Note 3 to entry: In this document all integrals are referring to a lower wavelength of 380 nm and to an upper
wavelength of 780 nm, corresponding to the definition range of Table 2.
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3.4
α-opic efficacy of luminous radiation (of a light source)
K
α,v
quotient of the α-opic radiant quantity of a light source (with known spectral composition) to the
corresponding photometric quantity
∫ X λ ⋅⋅sdλ λ
( ) ( )
e,λα
K = (2)
α,v
KX⋅∫ λ ⋅ V λ ⋅ dλ
( ) ( )
m e,λ
-1
Note 1 to entry: The unit of the α-opic efficacy of luminous radiation (of a light source) is W·lm .
Note 2 to entry: K can be expressed as ratio of the α-opic radiant flux (Φ ) to the luminous flux (Φ )
α,v e,α v
Φ
e,α
K = (3)
α,v
Φ
V
When the fluxes are expressed per unit area, Formula (3) equals the quotient of the α-opic irradiance to the
photopic illuminance
Note 3 to entry: For practical reasons it is recommended to modify the unit to W/klm or to mW/lm.
Note 4 to entry: For the special case of a light source with characteristics of standard illuminant D65,
D65
Formula (3) defines the α-opic efficacy of daylight K .
α,v
D65
Φ
e, α
D65
K = (4)
α,v
D65
Φ
V
3.5
α-opic irradiance
E
e,α
α-opic radiant flux per unit area
Φ
e,α
E = (5)
e,α
F
where
F is the area which is uniformly irradiated by Φ
e,α
-2
Note 1 to entry: The unit of the α-opic irradiance is W·m .
Note 2 to entry: α-opic irradiance is usually measured in the outward-facing plane normal to the optical axis at
the outer surface of the eye.
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3.6
α-opic equivalent daylight (D65) illuminance
D65
E
v, α
D65
illuminance E of a light source with spectral characteristics of standard illuminant D65 that
v, α
provides an equal α-opic irradiance E as the test source
e,α
E
e,α
D65
E = (6)
v, α
D65
K
α,v
Note 1 to entry: The unit of the α-opic equivalent daylight (D65) illuminance is lx.
Note 2 to entry: Examples for the melanopic equivalent daylight (D65) illuminance of different light sources at
the same photopic illuminance are given in Table A.2.
3.7
α-opic daylight (D65) efficacy ratio (with luminous radiation)
D65
γ
α,v
ratio of the α-opic efficacy of luminous radiation K of the test light condition (Formula (3)) to the α-
α,v
D65
opic efficacy of luminous radiation of daylight (Formula (4))
K
α,v
K
α,v
D65
(7)
γ =
α,v
D65
K
α,v
Note 1 to entry: The unit of the α-opic daylight (D65) efficacy ratio (with luminous radiation) is 1.
D65
Note 2 to entry: γ can also be expressed as the ratio of the melanopic equivalent daylight illuminance to the
α,v
photopic illuminance of the test light condition. It can also be expressed in percent, where 1 equals 100 %. In this
D65
case the value of the α-opic daylight (D65) efficacy ratio γ in percent is equal to the value of the α-opic
α,v
D65
equivalent daylight illuminance E of a test light condition S that delivers a photopic illuminance of 100 lx.
α,v
D65
Note 3 to entry: For the case that α denotes melanopsin, γ can alternatively be denoted as the melanopic
mel,v
daylight (D65) efficacy ratio (MDER) of the test light condition. In this case MDER should be given as a number
instead of a percentage. Some MDER values for different light sources are given in Table A.2. By multiplying the
photopic illuminance of a test light condition measured in lx with MDER, the value of the melanopic equivalent
daylight illuminance in lx is obtained.
3.8
circadian rhythm
biological rhythm with a period of approximately 24 h
Note 1 to entry: Biological rhythms are endogenous and affect psychology, physiology and behaviour.
Note 2 to entry: The sleep/wake cycle is an example of an endogenous circadian rhythm.
[SOURCE: CIE S 017/E: 2011 17-176; modified: notes to entry added]
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3.9
circadian entrainment
synchronisation of the circadian rhythm of a biological organism to an environmental parameter that
varies cyclically with a period of approximately 24 h
Note 1 to entry: In most conditions the natural (or artificially induced) light-dark cycle is the environmental
parameter that dominates circadian entrainment. Desynchronicity between the endogenous circadian rhythm and
the experienced natural, and/or artificially induced, photoperiod causes disruptions in the sleep/wake cycle (e.g.
jet-lag and shift work).
3.10
intrinsically-photosensitive retinal ganglion cells
ipRGCs
retinal ganglion cells that have intrinsic photosensitivity that is mediated by the photopigment
melanopsin
Note 1 to entry: The ipRGCs are sometimes denoted as photosensitive retinal ganglion cells (pRGCs), or as
melanopsin expressing (or melanopsin containing) retinal ganglion cells.
3.11
non-visual effects
NV effects
non-image-forming effects
NIF effects
eye-mediated light induced physiological and psychological responses or effects of light which are
broadly distinct from visual perception, and are considered to be mainly driven by the ipRGCs
Note 1 to entry: Non-visual (NV) effects of light are sometimes denoted as non-image-forming (NIF) effects of
light. Both terms are equivalent. Another term in use is “biological effects”. Use of this term is not recommended as
also vision is based on biological mechanisms.
Note 2 to entry: Sometimes the term “melanopic effects” is used to denote non-visual effects. Use of this term is
not recommended as a general synonym for NV effects, because it would ignore the influences of other α-opic
photopigments on NV effects.
3.12
melanopsin
photopigment responsible for the intrinsic photosensitivity of ipRGCs, both in humans and in many
animals (α = “mel”)
Note 1 to entry: Sometimes the abbreviation “z” is used instead of “mel” as value for “α” to denote melanopic
effects. “z” is the abbreviation for “Zeitgeber” which symbolizes the influence of melanopic effects on the human
circadian system. It is recommended not to use “z” in order to have a more clear symbol relating to melanopsin
and because also other photopigments may have an influence on the circadian system under certain conditions.
4 Non-visual effects of light
4.1 General
Light is the primary environmental signal that synchronises the endogenous sleep-wake cycle and other
circadian rhythms to the rotation of the Earth. Light exposure is able to shift the rest-activity pattern to
an earlier or later timing in the next circadian cycle. Morning light exposure typically advances the
circadian rhythm, whereas evening light usually delays the circadian rhythm. Apart from these
circadian effects, light can also induce acute changes in human physiology and behaviour, either during
or immediately after the light exposure. Examples include hormone secretion, heart rate, sleep
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propensity, alertness, body temperature, retinal neurophysiology, pupillary constriction, gene
expression and brain responses like neuronal activity or subsequent ability to concentrate [12].
Moreover light has proven to be effective in treating seasonal and non-seasonal depression [2][3][4].
The above circadian and acute effects of light are eye-mediated but the photoreceptive system involved
is not directly related to vision and presents several features that distinguish it from the visual system.
Therefore, they are referred to as non-visual, biological (or non-image-forming, NIF) effects of light. The
spectral sensitivity for nocturnal melatonin suppression in dim light adapted human subjects [5][6] and
aspects of the pupillary light reflex are reported to peak in the blue part of the spectrum, and the action
spectrum cannot be described by the established rod and cone photometric units. Human studies
contrasting blue and green exposures have established greater responses to blue light for some NIF
effects [7][8][9][10]. Taken together, the analysis of studies in humans indicates that for many NIF
effects the sensitivity to light peaks between 460 nm and 500 nm, in the blue-green part of the
spectrum. Examples include changes in the timing of the rhythm of melatonin, acute suppression of
melatonin secretion, elevation of body temperature and heart rate, reduction of subjective sleepiness
and improvement of alertness.
Moreover, the mammalian eye does not require rods and cones for the alignment (entrainment) of
circadian rhythms to the light–dark cycle [11]. A population of directly light-sensitive ganglion cells
within the eye acts to detect the spectral intensity in the blue spectral range, corresponding to
brightness of daylight and suffices to regulate both circadian rhythms and pineal melatonin secretion. It
is now known that a melanopsin containing photoreceptor system in the retina, distinct from the rods
and cones, plays a key role in mediating many of these non-visual, biological effects of light.
Today's lighting standards are based on rod- and cone-photoreception mediated visual aspects of light
only. The recently established melanopsin photoreception pathway is not included in current lighting
metrics and standards. This is an omission as the melanopsin-containing ipRGCs appear to be key
mediators for many non-visual biological effects of light. Therefore, melanopsin-related photoreception
needs to be taken into account when predicting and quantifying NIF effects of light. Rod and cone
photoreceptors can also contribute to NIF effects of light via mechanisms that are still not fully
understood. The interplay of the rod and cones with the ipRGCs is complex and probably varies with the
light intensity, exposure duration, prior light exposure and individual parameters like circadian phase.
A necessary step to enable a deeper understanding of the lighting conditions that lead to a specific
biological response, is to exactly characterize the stimulation of all photoreceptors that make up the
input for the biological system. Scientific studies indicate that all retinal photoreceptors can, under
different conditions, contribute to this input. For many NIF effects the ipRGCs seem to be playing an
essential role. This applies for circadian effects like melatonin suppression, circadian phase shifting or
circadian rhythm stabilization when using typical, daily life, lighting conditions. Also direct alerting
effects of light are known to have a higher sensitivity for shorter wavelengths of light, which is
consistent with the assumption that ipRGCs contribute strongly to these effects.
4.2 Characterization of light regarding non-image-forming effects
4.2.1 Measurement of spectral power distribution
Knowing the spectral power distribution is important for researchers carrying out studies on NIF
effects, for manufacturers developing specific lamp technologies, and for lighting designers, employers
and others who seek to predict the non-image-forming effects of optical radiation in specific
environments.
Spectral measurements are required when the spectral radiance of a source of light is unknown. Often
the spectral irradiance incident on the cornea of the eye is a complex combination of the spectral
irradiance from a number of sources, including light that can be reflected from a number of surfaces.
Such sources can include natural daylight and especially then the spectral irradiance incident on the
cornea of the eye can change with time.
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SIST-TP CEN/TR 16791:2017
CEN/TR 16791:2017 (E)
The spectral irradiance incident on an outward-facing plane normal to the optical axis at the outer
surface of the eye at the cornea shall be determined in the wavelength range 380 nm to 780 nm. For
non-visual effects, the irradiance at the retina is much more relevant than the irradiance at the cornea.
However, a measurement of light at the cornea provides a first useful approximation to estimate the
retinal irradiance of a light condition.
For a detailed assessment of the light situation additional parameters (e.g. luminance, dimensions of the
light source) can be relevant.
4.2.2 Determination of each of the photoreceptor inputs
The systematic set of five quantities to characterize the five photoreceptor inputs that can contribute to
the non-image-forming effects of light are based on the sensitivity functions of the five photoreceptors’
photopigments in the periphery of the retina to irradiance at the surface of the eye is defined in Table 1.
Table 1 — The photoreceptors of the human retina, their designation and formulae
for α-opic irradiance, reproduced and modified
Photoreceptor Photopigment α-opic irradiance α-opic irradiance
(label, α) -2
E (W·m )
e,α
S-cone S-photopsin (sp) S-photopic -2
E (W·m )
e,sp
irradiance
M-cone M-photopsin M-photopic -2
E (W·m )
e,mp
(mp) irradiance
L-cone L-photopsin (lp) L-photopic -2
E (W·m )
e,lp
irradiance
ipRGC melanopsin melanopic -2
E (W·m )
e,mel
(mel) irradiance
Rod rhodopsin (rod) scotopic irradiance -2
E (W·m )
e,rod
The spectral sensitivity functions for the standard human observer are given in Table 2.
The sensitivity for co
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