CHAPTER 3 EXPERIMENTAL METHODS
3.3 A DOPTING A NEW DECISION METHOD FOR PREVIOUS FINDINGS
The substance of this method is that the observer’s task is to decide whether the presented colour patch in the 2nd viewing condition (decision colour) is the colour seen before or it is not. This method is very easy to do for the observer.
3.3.1 Deciding photo experiment
The deciding photo experiment is the first experiment of the third series (7th row in Table 3.1). The most important advantage of the method of deciding is that very similar viewing conditions can be ensured for the "original" colour and the "decision" colour, in the 1st and 2nd viewing condition. All visual experiments were carried out on a well calibrated and characterised colour monitor in a dark room. 10 colour normal observers took part in the experiment. In this experiment, greyscale photo-realistic images were used as contexts. The pictures are shown in Figure 3.3.1. The black rectangle on the pictures contained the original colours (or colour centres) that the observer had to memorize. In the first viewing condition each of 10 colour normal subjects observed 3 different greyscale photo-realistic images containing "grass", "Caucasian skin" and "sky"
photos (the presentation sequence of the photos was the following: grass, skin, sky, grass, skin ... etc. with 50 repetitions each). First, a greyscale photo containing the original colour was presented. The original colour was a uniform rectangle patch in a black frame on the images, see Figure 3.3.1. These colours were found as nearly prototypical colours in previous experiments; see 1st-6th rows in Table 3.1. The determination of the original The so-called “deciding photo”, “deciding colour patch” and “simultaneous” experiments (see 7th-9th rows in Table 3.1) are the third stage of the evolution of experimental methods in my study. These together form the third series of the experiments. All images were displayed in a dark room, on a well-characterized and calibrated HP P1100 21'' colour monitor. The reference white (x=0.33; y=0.33; Y=54 cd/m2) was always displayed around the images. Subjects were adapting to this viewing situation for at least 2 minutes. The observers got only a short oral instruction about their task, which was confined to the substance of the task. They were not given any other information about the purpose of the experiment.
colours can be found in the results section of this experimental series (Section 4.3). There s, a full-screen uniform
middle-grey image was displayed. The observer had to make his/her decision with pushing the appropriate button.
was a 4 seconds time limit to memorize the colour. After thi
middle-grey image was displayed for 4 s. Then the same greyscale photo-realistic image was seen with an actual colour at the place of the original colour. 50 actual (or decision) colours were used for each type of colour centres, so an observer had to make 3*50 decisions during the experiment. The actual colours were chosen as random colours so that the colour difference between the colour centres and the actual colours were less than 20 and ∆L* was equal to zero. The decision colour was allowed to be the same as the original colour. The observer had to decide whether the just-seen actual colour is equal to the original colour or not. The deciding colour was seen for 4 seconds and then a full-screen uniform
Figure 3.3.1 For the deciding picture cue the uniform colour patch of the original colour and the deciding colour were displayed together with the image context: they were
displayed as a part of a greyscale photo-realistic image. The original colour was displayed in a black frame. Three examples: first row: grass, middle row: Caucasian skin
and last row: sky.
3.3.2 Deciding colour patch experiment
The description of this series can be seen in the 8th row of Table 3.1, called “deciding colour patch”. 10 colour normal subjects (same subjects took part as in the deciding photo experiment, described in Section 3.3.1) observed the three colour centres or original colours as alone standing colour patches. The colour centres were the same as in the previous deciding photo experiment. All colour patches were placed at the centre of the screen. The experimental process was also the same. An example for the alone standing colour patch
Figure 3.3.2 Example for the colour memory cue, subjects observed alone standing colour patches.
3.3.3 Simultaneous experiment
The reason of making the simultaneous experiment in this experimental series was to make a comparison between the results of the different types of experiments. This experimental type is a colour discrimination experiment. In the simultaneous series, the o
des an
question whether the two patches w our. One of the two colour patches was called "colour centre" and the other was called "decision colour". The colour centre was one of the three colour centres used in the deciding picture or in the deciding colour
is shown in Figure 3.3.2.
bserver saw two colour patches with 2º viewing angle on a grey background. The cription of this series can be found in the 9th row of Table 3.1. Figure 3.3.3 is example for the picture the observer saw. The observer’s answer was “yes” or “no” to the
ere of the same col
patch experiment. Naturally all colour centres were applied in this series too. The observer had to decide about 3*50 colour pairs whether they were the same.
ple for the simultaneous cue, subjects observed two colour patches.
In this series these three experiments embody the third stage of the advancem emory matching experimental method. First each observer carried ltaneous series, then, after 1-2 days, the deciding colour pa
eeks, the deciding picture series. The aim of the time
inimise the learning effect. There was 4500 decisions altogether: 10 observers * 3 series * 3 colour centres * 50 decision colours.
Figure 3.3.3 Exam
ent
of an appropriate m out
the simu tch series, and then,
after 2-3 w intervals inserted
between the series was to m
ed the equal viewing situation in the 1st and 2nd conditions, but it is very easy for the
observer. xing methods the equal conditions were also
The advantage of the decision experimental method was not only that it ensur
In the previous series at the mi
ensured, but the pursuit to mix the appropriate colour was really straining for the observers. With the application of the simple binary decision method, the procedure became more effective and less demanding.