E Visual Perception

ERCO Light Knowledge

People absorb most of their information from

the surroundings through the eye. Light here
is the precondition and medium for seeing.
Fundamental knowledge of human visual per-
ception is the basis for lighting design orient-
ed to Human Centric Lighting.

Our white paper summarises the essential

aspects of visual perception for you and pro-
vides helpful information and suggestions for
your everyday lighting design: find out how
visual perception functions physiologically,
what effects it has on psychological aspects
and how you are able to influence vision with
light.

Edition: 01/2022 | Current version at www.erco.com

E Visual Perception
Contents

How we see 3

Visual performance 5

Angle of vision 6

Contrast vision 7

Photopic, mesopic and scotopic vision 9

Glare 10

Shape perception 12

Constancy phenomena 16

Perceptual psychology 19

More expertise for your lighting design 21

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E Visual Perception
How we see

People absorb most of the information about

their environment through the eye. Light
here is not only a precondition and medium
for seeing, but via its intensity, distribution
and properties it creates specific conditions
that influence our perception. But what does
visual perception actually mean here? How
does it work? And what is the significance of
perceptual psychology?

What is meant by visual percep- Visual perception is a psychological process

tion? by which people inform themselves about
the objects in their environment through the
medium of light, and which is fundamentally
influenced by the three factors of light, object
and perceiving subject.

How does visual perception In the eye, an inverted image is projected onto In the human eye, there are differences be-
work? the retina via a deformable lens. From the ret- tween the perceived object and the image on
ina the image is then transported through the the retina: the image is spatially distorted by
optic nerve to the brain. The brain turns the projection onto the curved surface of the ret-
recorded image around again and processes ina (spherical aberration). Also, the spectral
the information. This principle is also imitated colours are reproduced incorrectly (chromatic
by a camera – the aperture assumes the func- aberration). This occurs because light of differ-
tion of the deformable iris. Image sensors are ent wavelengths is unequally refracted, caus-
modelled on the light-sensitive retina. Here as ing rings of colour around the objects. The
well, the image is upside down and is shown brain removes these aberrations during the
on the display the correct way up again due to further processing of the image.
computing.

Spherical aberration: depicted objects are distorted by Chromatic aberration: blurred image due to different
the curvature of the retina. refraction of the spectral colours.

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E Visual Perception

What is visual perceptual Perceptual psychology is a branch of science Before objects are assigned properties, they
psychology? concerned with the various aspects of visual must first be recognised, i.e. distinguished
perception, especially neural reception and the from their surroundings. From the process of
processing of sensory stimuli. To comprehend interpretation, laws of shape perception can
optical perception, the process of building up be formulated, according to which particular
visual impressions is of particular importance. arrangements are grouped into figures or
Apparent 'mistakes' enable an analysis of the objects. The laws of shape are also of practical
modes of action and objectives of perception. interest to lighting designers: each lighting
installation consists of an arrangement of lu-
On the one hand we have constancy phenom- minaires, be these on the ceiling, on the walls
ena. Constant objects generate images of dif- or within the space. However, such arrange-
ferent shape, size and brightness distribution ments are not perceived directly but organised
on the retina due to changes in e.g. lighting, into figures according to the rules of shape
distance or perspective. The mechanisms of perception. The surrounding architecture and
constancy perception compensate for these lighting effects of the luminaires create fur-
deviating retinal images. ther patterns integrated into the perception.

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E Visual Perception
Visual performance
Visual performance is the ability to perceive
and identify objects or small details and visual
tasks which have low contrast to the sur-
roundings.

What does visual performance Visual performance is the term used to An example:
mean? describe the perceptual performance accom- the lower the colour- or brightness contrast bet-
plished by the eye. The difficulty of a visual ween printed text and a sheet of paper, the more
task increases upon reduction in colour- or difficult it is to read the text. The same applies to
small font sizes.
luminance contrast and size of the detail.

What is the difference between visual perfor­

mance and visual task?
The visual performance must be accomplished
by the eye as the visual organ, so that the per-
son can fulfil the visual task required (e.g.
reading, writing or drawing).

What influences visual perfor- The brighter it is, the higher our visual perfor- The guideline values for illuminances at work-
mance? mance. At an illuminance (measured in lux, lx) places, as specified primarily in EN 12464,
of 20lx, we can only just distinguish people's range from 20 to 2,000lx within the frame-
facial features. Simple work, such as a meeting work outlined above. Recommended illumi-
in a conference room, already needs at least nances in individual cases depend primarily on
200lx, whilst complicated visual tasks, such as the size of the visual task and its contrast with
control tasks or precision assembly, require up the immediate surroundings, whereby very
to 2,000lx. Illuminances of even up to 10,000lx small, low-contrast visual tasks require the
are required in special cases such as opera- highest level of illuminance.
tions in hospitals.

Good to know:
Fundamentally, visual performance increases
abruptly with increasing illuminance. How­ever,
above 1,000lx it increases only slowly to then
finally decrease at very high illuminances due to
the occurrence of glare.

Influence of illuminance E on relative Influence of illuminance E on visual Visual acuity S according to age (nomi-
visual performance P for simple (upper acuity S of normal-sighted observers nal values)
curve) and difficult visual tasks (lower
curve)

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E Visual Perception
Angle of vision
The angle of vision is the angle at which a
viewed object is perceived. The reciprocal of
the angle of vision is the visual acuity (Visus)
and therefore, among other factors, a measure
of the legibility of writing.

How can the angle of vision be In order to measure visual acuity, a test per-
Good to know:
calculated? son must determine the orientation of the The unit of the angle of vision å is specified in
gap in a so-called Landolt ring (a circular ring angular minutes. An angle of one degree can be
with a gap or opening as a standard optotype divided into 60 angular minutes (1' = 1/60°).
or vision mark for vision tests). The angle of
vision can be calculated from the size of the
gap in the ring and the viewing distance. The
observation distance results in an angle of
vision (å), the reciprocal of which is the meas-
ure for visual acuity (S = 1: å). A visual acuity
(Visus) of 1 equates to recognition of the gap
under an angle of vision å = 1'.

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E Visual Perception
Contrast vision
Contrast vision is the visual process of perceiv­
ing the difference in brightness (luminance)
or colour between two objects, or between an
object and its surroundings. To be able to see
an object, it needs a sufficiently high contrast
to its surroundings. This should ideally be at
least 2:1. The lower the contrast, the more dif-
ficult it is to distinguish between two shapes.

Interesting facts about contrast vision:

Contrast vision is a function of vision closely related to visual acuity. Both functions, however, are not iden-
tical: contrast vision allows us to distinguish objects from each other to perceive them. Visual acuity on the
other hand refers to how well we can recognise contours and details.

What is meant by brightness Whether an object is judged as bright or dark

contrast? depends less on its absolute brightness (lumi-
nance), and more on its brightness in con-
trast to its surroundings. For example, a dim-
ly lit object can seem bright in a dark room.
The contrast in brightness is high. On the oth-
er hand, the object in bright surroundings but
illuminated in the same way is hardly notice-
able. The strongest light to dark difference in
contrast vision is between a white and black
surface.

Constructing hierarchies via brightness contrasts:

No hierarchy can be recognised anymore with The differentiation can no longer be clearly Significant differentiation can be recognised
a 1:2 difference in brightness between the recognised if the brightness contrast between with a brightness contrast of 1:10 between
surroundings and the object. The room thus the surroundings and accenting is approxi- the surroundings and the accenting. A very
looks monotonous. mately 1:5. The attention of the observer is no dramatic atmosphere is thus created. Light
longer so distinctly guided. and shadow characterise this intense accent
lighting.

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E Visual Perception

What is contrast rendering? Contrast rendering is a criterion for limiting

reflected glare, and is thus a criterion of qual-
ity in lighting design, e.g. for the legibility
of text. Contrast rendering is defined by the
contrast rendering factor (CRF). This is the
relation­ship between contrast of the visual
task at a given illumination to the luminance
contrast at a reference illumination.

Type of visual task Contrast rendering CRF level CRF mean value CRF minimum

mainly glossy materials, high 1 1.0 <CRF >0.95

e.g. graphic works

Satin matt materials, medium 2 0.85 <CRF <1.0 >0.7

e.g. in offices and schools

Work with matt material low 3 0.7 <CRF <0.85 >0.5

Is it possible to have no contrast? We talk about loss of contrast when differ­ences Winter sports people, especially skiers, are familiar
in luminance no longer exist. A distinction is with whiteout and they colloquially call it 'snow
made between two types of contrast loss: blindness'. Ground covered in snow, a bright hori-
zon or snowfall can make it difficult or impossible
to see your own surroundings. This is where cont-
- Blackout: black objects in very dark to black rast vision no longer functions.
surroundings can no longer be recognised.

- Whiteout: white objects in white or very

bright surroundings can no longer be seen in
a differentiated way.

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E Visual Perception
Photopic, mesopic and scotopic vision
Photopic vision Photopic vision is also colloquially known as
(day vision) day vision. In contrast to scotopic vision (night
vision) and mesopic vision (twilight vision),
photopic vision consists of visual perception
when there is sufficient brightness and is per-
formed via the cones in our eye. This enables
us to recognise colours. Due to the concentra-
tion of cones being highest in the foveal area,
daytime vision also has high visual acuity.

Good to know:
Experts speak of photopic vision when the eye
adapts to luminances exceeding 3cd/m2.

Mesopic vision Mesopic vision is the transitional state from

(twilight vision) seeing by day (photopic vision) using the
cones, to seeing by night (scotopic vision)
using the rods. This is why it is also called twi-
light vision. Upon decreasing brightness, our
colour perception and visual acuity deteriorate
until we finally only recognise differences in
brightness.

Good to know:
Experts speak of mesopic vision between lumi­
nances of 3cd/m2 and 0.01cd/m2.

Scotopic vision Scotopic vision is also colloquially referred

(night vision) to as night vision. This type of vision is per-
formed with the rods in the eye. As these are
mainly located in the peripheral areas of the
retina, visual acuity is low. In contrast to cone-
based vision during the day, no colours are
perceived. When seeing at night, we only rec-
ognise differences in brightness. However, this
means we are very sensitive to movements in
the peripheral field of vision. Twilight vision
(mesopic vision) lies between night vision and
day vision.
Good to know:
Experts speak of scotopic vision when the eye
adapts to luminances of below 0.01cd/m2.

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E Visual Perception
Glare
An essential characteristic for the quality of a
lighting system is the limitation of glare. Glare
is understood to be both the objective reduc-
tion in visual performance and the subjective
disturbance caused by the occurrence of high
luminances or high luminance contrasts in the
field of vision. The opposite of glare is visual
comfort.

What is glare? Glare is a general term for the reduction of Glare can be caused by the light source itself
visual performance or the disturbance of per- (direct glare) or by reflection of the light source
ception, as caused by high luminances or (reflected glare).
contrasts in luminance within a visual envi-
ronment. A distinction is made between phys-
iological glare, in which there is an objective
reduction of visual performance, and psycho-
logical glare, where perception is subjectively
disturbed due to a disparity between the lumi-
nance and the information content of the
area viewed.

What types of glare can occur? Both physiological and psychological glare
occur in the two forms of direct glare and
reflected glare. With lighting design, this is
relevant for e.g. the illumination of workplaces
or for street lighting.

With glare for office workplaces, a

differentiation is made between:
- Direct glare, primarily caused by
luminaires (1),
- Reflected glare on horizontal visual
tasks (2), and
- Reflected glare on vertical visual tasks,
e.g. screens.

Direct glare considers the ceiling area in front

of the viewer viewed at angles shallower than
45°. Reflected glare is glare which causes an
unpleasant visual disturbance directly in front
of the viewer, mainly caused by luminaires
in the ceiling area. A special case is reflected
glare on screens. Here, glare is mainly caused
by sources of glare light in the ceiling area
behind the viewer. With office workplaces, the
UGR method (Unified Glare Rating) can be
applied to determine the glare for a specific
viewer position.

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E Visual Perception

What are the possible conse- In the case of objective reduction in visual
quences of glare? performance, the term physiological glare is
used. Here, in the eye the light from a glare
light source is superimposed on the lumi-
nance pattern of the actual visual task, thus
impairing that eye's ability to perceive. How-
ever, the superimposition of spill light, which
is caused by the scattering of glare light in the
eye, is sufficient to reduce visual performance.
Increasing clouding of the eyes with age is
responsible for the higher glare sensitivity of
older people.

Absolute glare though, in the context of archi-

tectural lighting, is rarely a problem. In such
cases relative glare is much more frequent, The image shows an example of
in which the reduction in visual performance lighting that creates glare.
is not caused by extreme luminances but by
excessive contrasts of luminance in the field
of vision. Furthermore, unlike physiological glare, psy-
chological glare is a phenomenon relating
If the source of glare light does not cause an to information processing that cannot be
objective reduction in visual performance but described in detachment from the specific
only a subjective sensation of disturbance, context. For example, brilliance on crystal
this is termed psychological glare. The view chandeliers is an expected glare effect and is
of the observer is repeatedly drawn from the thus not perceived as physiological glare. The
visual task to the source of glare light, without situation is different with reflections on glossy
this area of increased brightness offering the paper. The reflection itself contains no infor-
expected information. Like an irritating noise, mation and superimposes itself on the printed
the source of glare light creates optical noise information.
that attracts attention and disturbs the per-
ception.

The constant, repeated adjustment to different

The extreme case of physiological glare is absolute
brightness levels and the different distance glare. This happens when luminances of more than
between the visual task and the source of 104cd/m2 are present in the field of vision, e.g.
glare light causes strain on the eye, which when looking at the sun or looking directly into
artificial light sources. Absolute glare is indepen-
is felt to be uncomfortable or even painful. dent of the luminance contrast to the surroundings:
Despite objectively constant visual perfor- it cannot be avoided by a brighter environment.
mance, psychological glare causes considera- To prevent the eye from being exposed to danger, a
ble discomfort, and the ability to perform, for protective reflex is triggered which causes the eyes
to close or even the head to be turned away.
example at the workplace, is reduced.

How can glare be avoided? A reduction of glare effects can initially be

achieved by reducing the contrast in lumi-
nance between the surroundings and the glare
light source. Therefore, either the brightness
of the surroundings have to be increased or
the luminances of the glare light source
reduced. However, it is more pre-emptive to
avoid glare by selecting luminaires with good
shielding and by correctly arranging the lumi-
naires.

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E Visual Perception
Shape perception and laws of shape
The term shape perception is understood as
a theory that assumes that visually perceived
structures do not result from single elements.
The observer sees or records these structures
in their entirety primarily as a shape, recog-
nised by a law of shape and separated from its
surroundings.

Laws of shape include:

- the law of symmetry
- the law of sameness
- the law of enclosure
- the law of the continuous line
- the law of good shape
- the law of equally wide shapes

What are laws of shape? To assign a property to a visually perceived arrangements are not perceived directly but
object, it must first be recognised, i.e. distin­ organised into figures according to the rules
guished from its surroundings. Laws are of shape perception. The surrounding archi-
derived from the process of interpretation or tecture and lighting effects of the luminaires
analysis, according to which specific arrange- create further patterns integrated into the
ments can be grouped into visually perceived perception.
figures or objects. The laws of shape are also
of practical use to the lighting designer: each
lighting installation consists of an arrange-
ment of luminaires, be these on the ceiling, on
the walls or within the space. However, such

What is the law of proximity? Shapes perceived as closed must not manda-
torily have a continuous contour. Elements
arranged near to each other can be grouped
together via shape perception according to
the 'law of proximity' to form a single figure.

In the example shown above, the observer

therefore first sees a circle and only afterwards
sees a ring-shaped arrangement of points. The
organisation of the points is so strong that the
imaginary connecting lines between the indi-
vidual points are not on straight lines but on
the circular line – the result being not a poly-
gon but a perfect circle.

Luminaires are joined together to become pairs. Four points become a square.

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E Visual Perception

What is the law of symmetry? In shape perception, one criterion for group
formation is symmetry. Particularly with
mirror-symmetrical arrangements around a
vertical axis, the mirrored shapes can each
be combined into pairs. This effect is some-
times so strong that the grouping of adjacent
shapes according to the law of proximity does
not take place.

An example: The arrangement of two square

shapes into four round shapes is reorganised into
two groups of five according to the law of shape
for symmetry.

What is the law of sameness? In addition to the spatial arrangement, the

structure of the shapes themselves is also
responsible for linking into groups. Thus in
the example on the right, the shapes are not
organised according to their proximity to each
other or possible axial symmetry, but on the
basis of identical shape

Interesting!
This principle of sameness also applies when
the shapes of a group are not identical but only
similar. For example, circles of different sizes are
perceived together. Rectangles and squares also
sometimes belong to a group due to their similar
shapes.

What is the law of enclosure? An essential principle of shape perception is

the tendency to interpret closed shapes as a
figure. Partly enclosed structures are also still
perceived as a figure.
A closed shape is always found on the inside
of the line that delineates it. This means that
the shape-forming effect of the line only
works in one direction. Usually this inner side
is identical with the concave, enclosing side of
a delineation.
This leads to the fact that even with open
curves or angles, a shape effect takes place
that makes a figure visible on the inside of the Important to know:
line, meaning in the partly enclosed area. If a Within an outline, complete enclosure is not
plausible interpretation of the initial pattern necessary to group the objects within it. The sug-
occurs in this way, the effect of the inner side gestion of a closed shape is sufficient to feign a
closed whole.
can be very strong.

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E Visual Perception

Experience and its resultant pre-expectation

are sometimes so strong that missing parts
of a shape are added or individual details are
perceived as changed in order to modify the
object to the expectation. Without a contour,
perception of the shape can succeed here only
on the basis of the shadow formation.

The experience makes it possible to recognise

the overall shape due to essential details being
made visible.

The principle also works with more complex

depictions such as a cube. The edges of the
figure are created in our brain according to
the law of enclosure.

What is the law of the continu- A fundamental law of shape perception is to

ous line? see lines preferentially as uniform, continuous
curves or straight lines. Interruptions, kinks
and branches are therefore avoided. The ten-
dency to perceive continuous lines is so strong
that it can influence the overall interpretation
of an image.

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E Visual Perception

What is the law of good shape? In the area of planar shapes, the law of the
continuous line corresponds to the law of
good shape or law of good continuation. Here,
shapes are organised to result in the simplest,
most orderly figures possible.

The arrangement of the points in the ceiling can be

joined into two lines according to the law of good
shape.

This arrangement is interpreted as two superimposed

rectangles.

What is the law of equally wide In the case of parallel, equally wide shapes
shapes? there is no strict symmetry, but a clear organ-
isational principle can be still recognised. This
leads to preferential perception as a figure. In
the example, the circles are interpreted as two
parallel lines because of their identical behav-
iour.

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E Visual Perception
Constancy phenomena
Constancy phenomena are processes of cor-
rection in vision and an essential precondition
for constructing an orderly image of reality.
Constancy in this sense is the ability to rec-
ognise constant objects, even when their size,
shape, reflectivity and colour or the surround-
ings change. These include, among other fac-
tors, changes in distance, spatial position or
lighting.

There are different forms of perceptual con-

stancy in vision. These cannot, to a certain
extent, be influenced or controlled. Types of
perceptual constancy include:

- Size constancy
- Brightness constancy
- Colour constancy
- Shape constancy
- Constancy of perspective

What all of these have in common is that

objects retain their colour, shape, size and
brightness despite changing conditions in
terms of surroundings and lighting.

What is perceptual constancy? The same object generates different retinal

images in the eye due to changes in lighting,
distance or perspective. For example, due to a
change in shape, size or distribution of bright-
ness. Perceptual constancy enables us to iden-
tify recurring objects and their properties and
to perceive these as being constant.

What is meant by size For visually perceiving size, a compensation

constancy? for the perspective distortion of objects takes
place. This ensures that e.g. rectangular or cir-
cular shapes as spatial phenomena are per-
ceived constantly: the observer can thus con-
stantly recognise regularly arranged circles on
the ceiling as being the same size, although
the circles visually shrink with increasing dis-
tance and look more like ellipses.

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E Visual Perception

What is brightness constancy? A further phenomenon of constancy is bright-

ness constancy. The perceived brightness
results from the ratio of brightness of the
object viewed and brightness of the immedi-
ate surroundings. For example, a medium grey
field with a dark surrounding is seen as being
light grey. If the surrounding is light, the field
appears dark grey. This phenomenon can be
explained by the direct processing of incoming
stimuli. This visual impression of two appar-
ently different shades of grey is exclusively
based on sensory impressions coming from
the outside.

What is colour consistency?

As with the perception of brightness levels,

colour perception is also dependent on
peripheral colours and the type of lighting.
The need for interpreting colour impressions
comes about mainly due to the constantly
changing light colours in the environment.
For example, a white sheet of paper is per-
ceived constantly both in the bluish light of
the sky and in warmer, direct sunlight. Colour
constancy in vision corresponds to the white
balance of film and photo cameras. Colour
photos taken under identical conditions with-
out white balance show the expected, distinct
colour casts of the respective type of lighting.

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E Visual Perception

What is meant by shape Constancy of shape, or form constancy, is also

constancy? one of the constancy phenomena. Our expe-
rience teaches us that gradients in luminance
from light to dark or vice versa can result from
the spatial shape of an illuminated object.
Examples are the formation of typical shad-
ows on three-dimensional bodies such as
cubes, cylinders and spheres.

The example of a hemisphere on a plane

demonstrates how the incidence of light and
the progression of shadows influence the per-
ceived shape:

the positioning of the light

incidence from above deter-
mines the spatial impression.

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E Visual Perception
Perceptual psychology
Perceptual psychology is a branch of science
that concerns the subjective aspects of per-
ception, mainly with the processing of re­
ceived sensory stimuli. With regard to vision,
the conditions of receiving visual information
are only fully comprehended by extending the
physiology of the eye to include the psycholo-
gy of perception.

Learn
- the importance of perceptual psychology in
vision,
- how people perceive their surroundings, Interesting to know:
- whether visual perception is innate, With vision, perceptual psychology together with
- the importance of experience in perceptual the physiology of the eye takes into account all
psychology, and factors in the interplay between
- the perceiving person,
- what is meant by subjective perception. - the objects seen, and
- light as the connecting medium.

What is the significance of per- The often applied model of the eye function­
ceptual psychology to seeing? ing as a camera cannot fully explain the
creation of the image perceived. It merely
transports the object to be perceived from the
outer world to the cortex, which is the part of
the cerebral cortex enabling vision.
For a real understanding of visual perception,
it is not so much the transport of image infor-
mation that is important but the conversion
or 'translation' of this information. This is
where perceptual psychology comes into play.
It supplements the physically recorded sensory
stimuli with individual components to thus
enable extensive perception.

How do people visually perceive The process of visual perception is split into
their surroundings? three steps:
1. Sensation and reception of stimuli: an
image of an object or the environment is
created on the retina of the eye.
2. Organising and evaluation of stimuli: In line
with shape perception, what is seen is com-
bined to create a coherent shape.
3. Ordering and interpretation of stimuli: a
meaning is assigned to the sensory impres-
sions.

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E Visual Perception

Is human visual perception The question of whether people's ability to There are indications for example that the
innate? perceive their environment in a contextual- spatial organisation of perception is innate:
ised or ordered way is innate (from birth) or if babies or newborn animals are placed on a
learned from experience cannot be answered glass plate that is above a step, they clearly
with complete clarity. Perceptual psychology avoid the area above the lower step. In this
splits here into several contradictory direc- situation, an innate visual recognition of
tions. Each of these directions can reference a depth and its associated danger takes prec-
range of evidence for its model, but none of edence over information from the sense of
these is able to plausibly explain all occurring touch which communicates a safe and flat
visual phenomena. surface.

What is the significance of expe- It appears that perception also depends on

rience in perceptual psychology? previous experience. Thus, familiar structures
are recognised more quickly than unfamiliar
ones. Already gained interpretations of com-
plex visual formations are kept to influence
future perceptions.

Experience and its resultant expectations are

sometimes so strong that missing parts of a
shape are added or individual details are per-
ceived as changed in order to modify the
object to the expectation.
Here, the principles of constancy phenomena
apply as part of visual perception.

Example of experience in perceptual

psychology:
in a perspective drawing, the two thick vertical
lines seem to have different lengths. This is
explained by the fact that the observer inter-
prets the drawing spatially. However, a line
that is further away must be larger than a
near line in order to produce an equally large
retinal image. The left line in the example
image is therefore interpreted and perceived
as larger in the spatial depth with effectively
the same length.

What is subjective perception? When people see, a form of selection or filter­ Conclusion:
ing occurs: the aim is to gain information In perceptual psychology, innate mechanisms and
about the surroundings but not to be over- one's own experience play a role. Presumably, the
whelmed by the abundance of sensory impres- innate component fundamentally organises the
perception. At a higher level of processing, the
sions. The perception is open to subjective experience helps to interpret complex shapes.
interpretation. The human brain converts
stimuli into perceptible images by applying its
own principles of order. Individual responses
to what is seen then follow.

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E Visual Perception
More expertise for your lighting design

ERCO offers a wide range of publications,

services and events on the subjects of light
and lighting design. Benefit from our ERCO
expertise to increase the quality of your archi-
tectural lighting.

ERCO Light Knowledge offers further com-

pactly prepared white papers on the various
topics.

Discover our other topics at

https://www.erco.com/de/lichtwissen

References The Lighting Design Manual –

an overview of the principles and practice of
architectural lighting.

Download manual as PDF:

https://lightfinder.erco.com/de/contentaccess/
page/download/media+handbook

White paper Human Centric Lighting –

the effect of light on people, their health and
well-being.

Download white paper:

https://www.erco.com/hcl

Lighting a green wall –

important notes on lighting design for
green walls.

Download white paper:

https://www.erco.com/greenology

Events & webinars Experience events worldwide & online –

Practice-oriented seminars on location or
online with lighting basics and knowledge
of lighting design.

Register now:
https://www.erco.com/events

ERCO Light Knowledge | White Paper Visual Perception 2022 21 / 21

Current version at www.erco.com