Efecto Bezold

EFFECT OF CHROMATIC ASSIMILATION (BEZOLD EFFECT) IN THE VISION OF THE CONTENT IN A DINNER PLATE

Ignacio TORTAJADA,1 Jorge MONTALVÁ,1 and Mariano AGUILAR1
1 Escuela Técnica Superior de Ingeniería del Diseño, Universidad Politécnica de Valencia



ABSTRACT

The colour perception of the olives, beans, anchovies... in a dinner plate depends of the colour and distribution of the othercontent.
In this paper we generalize this dependence analyzing how vary the vision of a gray rectangle seen through a monocromatic red grating in doing so the frequency and orientation of both.


1. INTRODUCTION

Daily experience shows that in the perception of a color, the surrounding areas or the areas intercalated in the object, have a great influence. In most cases this influence makes theobject vary towards the complementary colour of these disturbing areas, and this variation is known as simultaneous and spatial contrast (to distinguish it from temporary contrasts in the post-images) or chromatic contrast. If the disturbing areas (surround) are achromatic (white, grey or black) the contrast makes the object look darker or lighter.

With certain spatial distributions, the colorsintercalated can add to the object. This fact originally discovered by Chevreul (1839) was subsequently described by Bezold (1876), and is known as Bezold effect, Albers (1963), assimilation effect, Evans (1948), expansion effect or simply chromatic assimilation.


2. DISCUSSION

Without denying the possibility that the expansion effect could be justified physiologically as Hurvich and Jameson(1981) claim, due to the existence of receiving units of different sizes in the area where the image is formed, Cao and Shevell (2005) we believe this effect can be explained psychologically as per Gestalt theory, Wertheimer (1912). According to this theory, Rubin (1921), the vision is a consequence of the brain’s interpretation of radiant energy received from the total visual field, Aguilar andMateos (1996) . We always see objects as part of the set they are in (for example, in a marine landscape, any distant object will always be a boat.)

Many authors have intented to justify the Bezold effect, while for the study of the simultaneous contrast, the justifications are consistent in the scientific community, no such clear justification has been found for the assimilation effect, .Burnham (1953) made his experiences with drawings based on the original Bezold plates, noting that the Bezold effect appears by viewing displays with a lack of sharp focus. Helson (1963) claimed that assimilation occurs when there are small differences between inducing and test areas. On the other hand, Helson (1964) says that assimilation occurs when the inducing region is small relative to the testregion.

In our laboratory we are working on the same way as: Agostini and Galmonte (2000), Bressan (2001), White (1981), Economou, Annan and Gilchrist (1998). Because we believe that the Bezold effect can not be justified by the contrast theories.

Figure 2. Gratings used in the tests. Only the central sequence is analyzed.


3. EXPERIMENTAL TECHNIQUE

The tests have three grey straightparallel sequences with a width equal to their separation (1 cm.), these sequences have a Ronchi grating with 2cm. period covering 22 cm. side square in the background. The central sequence is superimposed over the red stripes of the grating and the lateral ones over the white stripes (figure 2).

It was checked that the lateral sequences with squares coinciding with the white lines experienceda color variation (redness plus saturation) due to the expansion effect (redness) and the direct contrast (redness and saturation increase). It was also checked that the central sequence with squares coinciding with the red lines experienced the opposite variation (saturation decreases and luminosity increases). Starting from a distance of 4 meters, the observers get closer until they cannot...