Optical center

Optical center is a term used in design theory and perceptual psychology . It describes a point that deviates slightly from the geometric center of an object and is optically perceived as the center due to an optical illusion , which must be taken into account in graphics and design , for example .

Optical center in graphics and design

Left: geometric center.
Right: optical center.
Format: A4

There is no absolute basis for calculating the optical center. It is often chosen by feeling during production.

The optical center is used wherever typographical , pictorial or content elements are to be placed vertically in the middle in a surrounding format . The optical center is more important if the elements are also centered horizontally.

Balance line

Left: Construction of the balance line according to Hallberg.
Right: application.
Format: A4

According to Hallberg, a balance line can be constructed around which the individual elements are grouped in a harmonious and balanced way in order to create a visual balance.

Let b be the page width (210 mm for A4 upright) and h its height (297 mm) as well as x the horizontal and y the vertical distance from the top left corner to the intersection of the rectangle diagonals (from top left to bottom right) with the square diagonal (from top right to left, corresponds to the quarter circle edge).

The height y of the balance line can be calculated using the ray theorem. The theorem of rays must be used for both the rectangular diagonal and the square diagonal. The theorem of rays for the rectangular diagonal is:

${\displaystyle {\frac {y}{h}}={\frac {x}{b}}\qquad \Longleftrightarrow \qquad x={\frac {b}{h}}\times y}$

Since the edge lengths of a square are the same, the theorem of rays for the square diagonal can be written as follows:

${\displaystyle {\frac {y}{b}}={\frac {b-x}{b}}\qquad \Longleftrightarrow \qquad y=b-x}$

Plugging the second into the first equation, y can be calculated:

${\displaystyle y=b-{\frac {b}{h}}\times y\qquad \Longleftrightarrow \qquad y={\frac {b}{1+{\frac {b}{h}}}}={\frac {b\times h}{b+h}}}$

For an A4 page, the result is from above or 174 mm from below, which corresponds exactly to the special aspect ratio (1 ∶ √2) . ${\displaystyle y={\tfrac {210\times 297}{210+297}}\,{\text{mm}}\approx 123\,{\text{mm}}}$ ${\displaystyle 2\times (297-210)\,{\text{mm}}}$

supporting documents

1. ↑ symmetry, asymmetry . Uta.fi. Retrieved July 13, 2010.