The document discusses the concept of visual weight in images, defined as the visual force arising from light contrast, and its center of gravity (cg), which indicates balance when aligned with the geometric center. It explains the distinction between partial and integral visual weight and how psychological and perceptual weights influence our perception of objects. The calculation of visual weight involves applying psychophysical relations, highlighting its importance in various artistic disciplines for enhancing visual composition.

1. VISUAL WEIGHT
Prof. Arq. Raúl Parada Castellano

2. The visual weight of an image is defined as the visual force that emerges due to the
contrast of light between the different elements that compose it.
The point where the visual weight of an image places is named the Center of Gravity (CG).
When the CG coincides with the Geometric Center (CC) of the image, we establish that the
image is balanced.
L * = Average lightness of the image (0 = total black /1=total white)
PVi = Visual Weight of the integral image (between 0 and 0.5
at integral figures)

3. HISTORICAL BACKGROUND
. Harvard University:
- Denman. W. Ross (1853-1935) ¨A Theory of Pure Design¨
- Rudolf Arnheim (1904-2007) ¨Art and Visual Perception: A Psychology of the Creative Eye¨
. Staatliches Bauhaus:
- Josef Albers (1888-1976) ¨Interaction of Color¨
- Johannes Itten (1888-1967) ¨The Elements of Color¨
At present:
Raúl Parada Castellano (2015) ¨Study of balance of images using visual weight¨

4. PARTIAL WEIGHT AND INTEGRAL WEIGHT
The visual weight is established as
¨partial¨ when we select a figure and
segregate it of the rest of the image
(bottom). Here, the weight depends
on the contrast power that the figure
creates respect of its bottom.
Partial weight of a duck figure
Integral weight of a set of figures
The visual weight is established as
¨integral¨ when the totality of the
image is interpreted as a figure. In
this case, the visual weight of the
image depends on the contrast power
on every visual element respect of
the average lightness of the image.
The visual weight does not need of any perceptual recognition in order that it appears.
Only it needs of a lightness interaction in the image, therefore, is formed as a direct and
omnipresent visual force.

5. THE PSYCHOLOGICAL WEIGHT
AND THE CONTRAST OF LIGHTNESS
The psychological weight is the sensation that everything
what we see is submitted by force of the gravity, since our
vision is totally accustomed and linked to the vital
conditions that limit us in our environment. Therefore,
any visual perceived element (though this one is abstract)
associates automatically a vertical force with down
direction.
Minor light contrast a figure creates respect of his bottom,
minor sensation of psychological weight we perceive. This
owes that the loss of contrast of lightness in a figure
provokes a loss in our capacity of visual recognition, and in
turn an increase in the visual sensation of levity, since this
one is faded away into the bottom as is losing its contrast.
Depending on the scene in which a figure is inserted, this one will be able to have a
different visual weight, which implies that the visual weight is variable depending on
the different factors of appearance that concern the scene.

6. PERCEPTUAL WEIGHT AND VISUAL WEIGHT
The perceptual weight is the weight that is
assigned to a visual object, after
recognizing it and to process it, that is to
say, it is the weight that we think mentally
that it can have an object independently of
the scene in which it is placed.
Whereas the visual (psychological) weight
is a direct sensation that appears
automatically in our visual (genetic)
processes, that is to say, it appears without
the conscious processing (subjective) of the
image. Thus, it depends on the light
interactions that appear in the entire
configuration of the image.
Black feather on clear bottom:
Example of contrast between a high visual
weight and a low perceptual weight
The perceptual weight is always the same one, whereas we do not have a new
experience relative to the object that modifies it.
On the other hand, the visual weight is variable, that is to say, it changes as the
factors of variability of appearance of the scene change theirs values.

7. DETERMINATION OF THE VISUAL WEIGHT
The calculation of the visual weight is realized establishing the following psycophysical
relation:
Physical Action (Light - Space) Sensory Action (Visual Sensation)
A) Sensory action due to the light:
1º- Light = Spectrum of reemission of every visual element  Quantity of light
2º- Spectral sensibility of the human vision to the light  Luminance
3º- Perceptual human response to changes of light  Lightness (L*)
B) Sensory action due to the space:
Space = Two-dimensional Surface Surface in which the light
reaches  Surface of the human frame (Sup)
Relation (light - space)  P = (L*/100) · Sup
Lightness Interaction Lr = │(Lf/100) – (L*/100)│ Relative Weight Pr = Lr· Sup
Quantity of light
Luminance
Lightness
- The surface of the visual human frame can be represented by the figure of a rectangle
to simplify its calculation. The total surface of the image is equal to 1, therefore, every
single element that composes it will have a surface between 0 and 1.
- The luminosity divides between 100 to obtain values between 0 and 1.

8. DETERMINATION OF THE GRAVITY CENTER IN AN IMAGE
Axes of reference of the image (X, Y).
The horizontal axis ¨X ¨ and the vertical axis ¨Y ¨ establish as
axes of coordinates of an image on the analogy of our axes of
visual reference.
Geometric Center of the image (CC)
Gravity Center in an image (CG)
The geometric center of the image is established as the point
that defines the center of the image. Therefore, it uses as
reference to determine the degree of balance of the image.
The gravity center is defined by the coordinates (XCM, YCM)
on the axes of reference where there places the resultant
force of the visual weight of the image.
mv1, mv2, …, mvn are visual masses, y xv1,xv2….xvn e yv1,yv2,..., yvn are coordinates of
the centers of the different visual masses to the axes of reference ¨X ¨ and ¨Y ¨ of
the frame of the visual image.

9. USEFULNESS OF THE VISUAL WEIGHT
The visual weight and the calculation of the C.G acquire the quality of important analytic tools
in the creation of any visual composition. In different artistic disciplines as for example; art,
painting, photography, cinema, graphical design, advertising, architecture, engineering and
design in general, the visual weight and the calculation of its balance are established as
systems of great value in the development of the creative composition.
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EXAMPLE OF PRACTICAL APPLICATION
How PV works:
Youtube; https://www.youtube.com/watch?v=X7yh67O4CqQ