Basic HTML Version
NORDIC LIGHT & COLOUR
109
METHOD
Experiment design
The experiment was conducted in the Daylight Laboratory,
under Artificial Sky, at the Department of Architectural Design,
Form and Colour Studies, NTNU. It enabled us to get stable
lighting conditions and equal illumination for all scale models
(Matusiak & Arnesen 2005). The experiments could be carried
out independent of weather conditions and time of the day.
The Artificial Sky installation simulates a standard model of a
perfectly cloudy sky, the CIE Overcast Sky in which the horizon
luminance is equal to 1/3 of the zenith luminance. The light is
produced by fluorescent light tubes of the Cool Daylight type
(PHILIPS MASTER TL5 HE 28W) (Matusiak & Arnesen 2005).
According to measurements conducted by architect Julie Guic-
hard in 2010 using “Spectra Scan 650”, the Correlated Colour
Temperature inside the Artificial Sky is 5500 (Salvesen et al.
2012) (see Figure 2).
Eight scale models of the rooms were prepared. The 1:20 scale
model 25cm × 35cm × 20cm represented a room 5m × 7m ×
4m, see Figure 3. The size was chosen to be large enough for a
comfortable observation as well as enable good conditions for
taking photos of the interior. The walls, ceiling and floor were
constructed using 1cm MDF boards. From the outside, the mo-
dels were painted in black colour which helps to avoid light pe-
netration from the Artificial Sky through splices of the boards.
The window frame was made of opaque white cardboard. The
models were also covered externally by black textiles to elimi-
nate light penetration from the outside during the observation.
The colouration of the walls in models was of two types, while
colours of the ceiling and floor were identical for each model
(see Figure 4, 5 and Table 1). The first type was striped pat-
tern, i.e. a combination of low saturated equiluminant colours
representing the chromatic contrast: red and green, yellow
and blue, blue and grey (see Figure 4). The width of the stripes
was 19 mm and according to the distance from the walls to the
observers` eyes (35 cm), this pattern has a spatial frequency
0.161 c/deg.
The second type of wall colouration was uniformal, one-co-
loured, with the use of the same colours as in striped patterns,
i.e. red, green, grey, yellow, and blue (see Figure 5). All the
paints were matte. It was decided to paint the ceiling of the
models in white colour and the floor in dark grey colour (see
Table 1), similarly to many real rooms. Moreover, these colours
are achromatic, which is an advantage in terms of studying
the effects of chromatic colours of the walls. First, orienta-
tion colours with similar luminous reflectance factor (Y
1
) were
chosen from the samples of the NCS Colour Atlas. Then paints
were mixed manually and wooden pieces were painted. After
drying, the luminance of each of them was measured using the
MINOLTA Luminance meter. The process was repeated until
equiluminance of the paints was reached, see Figure 6. The
final colours were matched with the NCS colour samples again
by two persons independently. In Table 1 you can find all the
colour notations according to the NCS system (NCS samples
that were the most approximate to used paints). Finally, all the
models were properly painted and prepared for the experiment.
Lighting measurements and reflectance calculations
Painted wooden samples were placed one by one in the center
of the Artificial Sky together with grey and white reference
cards for luminance measurements. Luminance, at the central
point of each sample and grey and white cards were measured
(see Figure 6). Afterwards the reflectance of each sample was
calculated according to the luminance readings of the referen-
ce cards. The illuminance was measured at the central point on
the floor inside each scale model when it was arranged under
the Artificial Sky (see Figure 3; 7; 12 and 13). It enabled us to
not only to get illuminance values in models, but also to check
and analyze differences of the lighting in terms of the models`
arrangement.
Survey and questionnaires
The experiment was conducted in September 2012 in the
Daylight Lab at the Gløshaugen campus of the Norwegian Uni-
versity of Science and Technology. All the scale models were
placed in the laboratory under the Artificial Sky, see Figure 3.
In total 32 observers were involved in the experiment. The sub-
jects were mostly master students of architecture (14), a group
of physicists (5), PhD Candidates in architecture (5), a group of
engineers in computer science (3) and few people from other
academic fields (5). The age of participants varied from 21 to
42 years, all of whom have normal colour vision. The models
were lit through a window facing the Artificial Sky. The interiors
of the models were observed through an opening made in the
wall opposite the window; see Figures 2, 9 and 10. Each subject
observed both groups of scale models (striped and one-colour-
ed models) and answered the questionnaires. The order of the
observation of one-coloured and striped models were random.
Therefore one group of subjects started with striped models,
while another part observed one-coloured models. This provi-
ded the necessary conditions for randomization. Randomized
design allows the experimenter to avoid statistical errors and
increase the chances of detecting differences among reactions
(Stamatis 2012: 114-115).