Technical Translation: Usability Strategies for Translating Technical Documentation

Visual Perception 
As mentioned above, only two physical properties of light are detected by 
the eye: intensity and wavelength. This “raw information” must be filtered 
and processed before it becomes meaningful input for the brain. 
The human eye is sensitive to light with a wavelength between 400nm 
and 700nm (Downton 1991:18). This wavelength range is known as visible 
light. We know that the eye is sensitive to the wavelength and the intensity 
128-150 distinct colours and 8 million different shades? (Downton 1991:18; 
Dix 1998:18). To understand this we need to examine the components of 
colour, namely, 
hue
, 
intensity
and 
saturation
. 
Hue corresponds to a superordinate class of colour, i.e. it is the same as 
what we mean when we say “colour” in everyday conversation. Hue is de-
termined by the wavelength of the light. So for example, blue light has a 
wavelength of approximately 400nm and red light has a wavelength of ap-
proximately 700nm. Intensity is the brightness of the colour and saturation 
is the amount of white in the colour. By varying these two components, it 
is possible to detect between 7 and 8 million different shades of colour. 
However, the number of colours which can be realistically detected by an 
untrained eye in isolation is in the region of 7-10 (Dix 1998:18; Downton 
1991:18). 
104 
(see page 103) of light so how do we distinguish between the approximately 

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The Human Cognitive System
Brightness is a subjective response to light. There are no absolute levels 
of brightness and our perception of it is determined by our own personal 
preferences, physical make-up and physiological state (e.g. migraine head-
aches make us more sensitive to light). Brightness is affected by 
luminance
which is the amount of light emitted or reflected from the surface of an ob-
ject. Unlike brightness, luminance is a physical characteristic and can be 
measured using a photometer (Dix 1998:18) and is quantified in 
candelas 
per square meter
(Faulkner 1998:19). In practical terms, this means that a 
brighter object (e.g. text) will be easier to see and read. However, increased 
brightness also makes the eye more susceptible to flicker (Faulkner 
1998:20). 
Contrast is related to luminance in that it is the relationship between 
light emitted by an object and the light emitted by the background. This is 
illustrated in Figure 3. 
Figure 3: Brightness contrast 
In this diagram, the small squares are all equally as bright as each other but 
because of the contrast with each of the backgrounds, the squares look 
brighter or darker depending on how dark the background is. 
Saturation is the amount of white light in a colour. But to fully under-
stand saturation, we must first look at the difference between 
chromatic
and 
achromatic
colours. Chromatic colours such as blue, red, green, etc. have 
hue and are affected by the wavelength of light. Achromatic colours, on the 
other hand, such as black, white and neutral grey do not have a hue and are 
not affected by wavelength (Faulkner 1998:17). 
Saturation refers to the extent to which a colour is chromatic or achro-
matic. The more achromatic colours go to making up a colour, the less 
saturated it becomes. A colour’s saturation is said to be zero when it is en-
tirely grey. 
105 

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Understanding Users