|
|
|
|
|
|
Visual
Acuity |
|
|
|
PROBLEM |
|
SOLUTION
|
Generalized
decrease
in
ability
to see
objects
and details
clearly |
|
1. Provide
appropriate
product illumination
and contrast.
The
light
on visual
displays,
particularly
for typography
and control
information,
should
provide good
legibility
while
using the
product (e.g.,
operating
controls
and reading
operating
instructions.) It
is important
to have
the source
of illumination
positioned
at a
low angle
to the surface
in order
to prevent
glaring
reflections
along
the operators
line
of light. Environmental
lighting
should
allow the
product's
form and
surfaces
to be easily "read." The
lighting
should
develop
a contrast
between
an object
and its
background
in order
to separate
the product's
form and
features
from the
immediate
environment. |
|
|
|
|
|
2. Consider
the object's
environment.
Design
to accommodate
known or
suspected
environmental
conditions
such as
poorly
lit enviroments,
distracting
textures,
and visual
clutter.
Isolate
priority
information
from
enviromental
background
value,
clutter,
and glare
by selecting
the appropriate
color,
value,
size,
and chromatic
intensity
for type,
graphic
symbols,
and their
respective
fields. |
|
Back
to
Top
|
|
|
|
|
Visual
Accommodation |
|
|
|
PROBLEM |
|
SOLUTION |
Specific
decrease in
abiity to focus
on nearby objects
or read
fine print
(presbyopia). |
|
1. Minimize
the need
for typography. |
|
In
many cases,
typography
can be eliminated,
or at least
minimized,
by substituting
simple, unequivical,
graphic symbols.
When
used they
should
be sized
and positioned
to communicate
the importance,
order,
and relationships
of the
product's
components,
controls,
and operating
sequence.
Irrelevant
information
and
decoration
(e.g.,
nameplates,
logos,
and extraneous
decorative
elements)
should
be eliminated
from
informational
surfaces. |
|
|
|
|
|
2. When
typography
is essential
for information
purposes,
make it legible.
In
general,
select
the largest
appropriate
size and
weight
of type
that will
serve the
intended
purpose,
and the
widest
appropriate
letter,
word, and
line spacing
that will
ensure
legibility.
Favor
san-serif
type
for non-text
material,
such
as display
type,
headings,
and numbers. For
maximum
readability,
use upper
and lower
case
type
and isolate
individual
information
messages
where
accurate
communication
of information
is important
(e.g.,
control
settings
and instructions),
determine
the size
of the
type
by the
expected
level
of illumination
and viewing
distances. Strive
to maximize
the contrast
between
the type
and its
field,
and avoid
using
ornate,
decorative,
or segmented
type
faces. In
order to
provide
clear
and
unambiguous
visual
messages,
use
redundant
cuing
when
possible
by
combining
type
with
graphic
symbols. On
dials,
use only
whole
numbers
and
a minimum
of
markings.
|
|
Back
to
Top
|
|
|
|
|
|
Visual
Threshold |
|
|
|
PROBLEM |
|
SOLUTION |
Difficulty
in seeing
objects in
dim light |
|
1. Provide
adequate
illumination.
Maintain
a visually
adaptable
environment
by providing
at least
the minimum
professionally
recognized
foot-candle
measurement
standards
for detail
work,
general office
work, instrumentation,
general
lighting,
and emergency
lighting.
When
possible,
provide
the operator/user
with
adjustable
control
of the lighting
environment
(e.g.,
rheostats,
adjustable
shades,
or changeable
filters). |
|
|
|
2. Illuminate
to reveal
contour of
form.
Changes
in surfaces
may be difficult
or impossible
to perceive
under certain
ligting conditions
(e.g., flat
lighting
or dim lighting).
In
order to
perceive
a product's
form
and/or reveal
its contours,
the environmental
lighting
level
should be
maintained
at one
third that
of task lighting. Where
it is important
to
clearly reveal
or communicate
the
contour and/of
texture
of a particular
surface,
locate
the light
source
at a low
angle to
that surface.
|
|
Back
to
Top
|
|
|
|
|
|
Brightness
Adaptation |
|
|
|
PROBLEM |
|
SOLUTION |
Inability
of the eye
to adapt
to excessively
bright light
or surface |
|
1. Reduce
excessive
illulmination.
Provide
illulmination
with intensity
levels that
are appropriate
for the indtended
use and in
line with
professionally
recognized
standards.
Provide
for a gradual
change
in light
levels between
widely differing
levels
of illuminated
surfaces
and environments. |
|
|
|
2. Avoid
over-saturation
of illumination.
Eliminate "hot
spots" by
ensuring
that critical
information
is evenly
illuminated. Avoid
using spot
lights for
general illumination.
Favor
indirect
light where
appropriate. |
|
|
|
Eye
loses its
ability to
distinguish
between dark
and light
surfaces. |
|
3. Provide
maximum appropriate
contrast.
Ensure
that all
critical
information
is evenly
illluminated
and isolated
from competing
background
clutter,
color, textures,
and glare.
Make
critical
indicators
stand
out from
among other
displays
by providing
contrasting
values,
colors, and
textures. Whenever
possible,
offer
the operator
a means
to control
the level
of contrast. Where
dark
adaptation
is
required
(e.g.,
darkrooms,
night
lights,
etc.),
use red illuminants. |
|
Difficulty
in adjusting
to bright
lights
(glare).
Back
to Top
|
|
4. Eliminate
glare.
Present
information
in a non-glare
mode by offering
non-reflective
surfaces,
providing
adjustable
illumination,
and designing
appropriate
shielding
of viewing
surfaces.
Also consider
the use of
polarizing
screens. |
|
|
|
|
|
Critical
Flicker Frequency |
|
|
|
PROBLEM |
|
SOLUTION |
Flashing
light may
be perceived
as steady.
|
|
Exercise
care in the
use of flashing
lights.
Use
flashing
lights
only for
specialilzed
applications (e.g.,
warning
or attention).
If flashing
lights
must be
used, use
a slow
rather
than a
fast flash
(do not
exceed
15 cycles
per second). Once
flashing
begins, maintain
the flashing
in order
to provide
a sense
of distance
between
the viewer
and the
flasher. Ensure
that
the color,
intensity,
and
frequecy
of the flash
is in marked
contrast
to
the backgrouond
environment. |
|
|
|
|
|
Hue
Perception |
|
|
|
PROBLEM
|
|
SOLUTION |
Inability
to differentiate
cool colors
(green /
blue /
violet).
|
|
1. Maintain
color contrast.
Avoid
using green/blue/violet
color combinations.
If
such combinations
must
be used,
use them with
care and
ensure
that
each
color
contrasts
the others
in value
(e.g.,
light
vs. dark)
and/or
chromatic
intensity
(bright
vs. dull). Strive
for color
combinations
which
use strongly
contrsting
colors
(e.g., yellow/blue). When
developing
and using
color-coding
systems,
avoid
confusioon
and misunderstanding
by applying
the system
in a
clear, consistant,
and unambiguous
manner. In
applications
were
sharp vision
is critical,
avoid
using blue
illuminants. |
|
Increased
perceptual
blending
of analogous
colors.
Back
to Top
|
|
2. Maintain
value contrast.
Avoid
using analogous
color combinations
like red/orange
or violet/red.
If
such combinations
must
be used,
use with
care
and develop
an artificial
value
contrast
wich
ensures
that
each color
contrasts
the others
in value
(e.g.,
light vs.
dark) and/or
chromatic
intensity
(bright
vs. dull). It
is particularly
important
to develop
high
contrast
where
accuracy
in speed
and reading
are required
(e.g.,
instructions
and warnings).
|
|
|
|
|
|
Chromatic
Perception |
|
|
|
PROBLEM |
|
SOLUTION |
Decresed
ability to
see color. |
|
1. Avoid
the use of
low chromatic
(dull) color
when color identification
is required.
It
is important
that high
chromatic
(bright)
colors
be used for
identity
applications
(e.g.,
color coding,
color identification,
and color
differentiation).
When
high chromatic
colors
cannot
be
used,
use
color with
care. Strive
for colors
that contrast
in value (light
vs. dark)
and/or
contrasting
colors
(e.g.,
yellow/blue). When
developing
and using
color identification
systems,
avoid confusion
and misunder-standing
by applying
these systems
in a clear,
consistant,
and unambiguous
manner.
In applications
where accurate
color reading
is important,
use white
light
as the illuminant. |
|
|
|
2. Maintain
value contrast.
Avoid using
colors of similar
value contrast
in side-by-side
or figlure/ground
applications.
If such
positioning
must be
used, use
with care and
develop
an artificial
contrast
which insures
that each
color contrasts
with the
other(s)
in value
(e.g.,
light vs.
dark) and/or
chromatic
intensity
(gright
vs. dull). It is particularly
important
to develop
high
contrast
where speed
and reading
accuracy
are required
(e.g.,
instructions
and warnings).
|
|
Back
to
Top
|
|
|
|
|
|
Field
of Vision |
|
|
|
PROBLEM |
|
SOLUTION |
Loss
of peripheral
vision
(tunnel vision). |
|
Accommodate
a decreased
field of
vision.
It
is important
that critical
information,
caution or
warning lights,
and sets
of analogous
controls
be clustered
within the
operator's
narrowest
appropriate
cone of vision.
Clustering
minimizes
the necessity
for shifting
the operator's
vision
while working
through a
sequence
of control
operations. Cones
of vision
should
be located
to correspond
to
the logical
(natural)
sequence
of the
operation. |
|
Rationalizations
can no
longer
excuse
designs
of products
or environments
that fail
to attract
and accommodate
any segment
of the
population.
*Courtesy
of "Guidelines
and Strategies
for Designing
Transgenerational
Products," was
suported, in
part, by Grant
number 90-AT-0182,
from the Administration
OIffice of
Human Development
Services, Department
of Health and
Human Services,
Washington,
DC 20201, and
the All-University
Gerontology
Center, Syracuse
University.
|
|