Shadow effect

Michelangelo Merisi da Caravaggio : The incredulous Thomas , 1601–02, oil on canvas; New Palace, Potsdam

In the performing arts as well as image processing, shadow effect refers to the representation of shadows .

Basics

While sculpture - right up to the relief - can fall back on actual shadows, representations in the surface in painting, photography, but also in modern image processing rely on an imitation in the sense of an optical illusion . The shadow cast by an object can be determined when designing an image using the methods of representing geometry .

Methods

sculpture

In the representation of shadows, the sculpture makes use of the spatiality of its work. Sculpture is also known as “playing with light and shadow”.

However, while painting and related representations can fix a certain desired shadow cast, the sculptor must expect that the lighting of his object will change when it is set up later. Therefore, he can only specify shadow effects within a certain framework.

In general, surfaces on sculptures or profiles with an exaggerated undercut can be designed in such a way that the shadow clearly emerges in large areas of changing light sources. Diffuse lighting is considered the "death" of every work. That is why exhibiting objects in the open air is valued , and adequate lighting is also a central aspect of presentation in museums , galleries and elsewhere.
Reliefs and other architectural elements such as stucco are usually designed in such a way that they receive their light in a defined manner from a side on which they are designed. Only south-facing reliefs on external facades have to be heavily undercut, which places special demands on cast stucco .

Construction of the shadow

The course of the light-dark border of the shadow is determined by the physical laws of optics, as a beam path from the light source via the object to the shaded area. The real conditions can be simulated constructively. Representing geometry deals with the construction of the shadow of a drawn object in a spatial or projective representation on the two-dimensional image plane . Shadows for central lighting, parallel lighting as well as penumbra for several sources can be constructed. Shadow conditions for diffuse light are structurally difficult to solve.

Shadow painting and graphic techniques

Shadow rendering techniques include:

Hatching , the classic shading technique for graphics , including all single-color printing techniques
Wash over line drawings and in watercolor techniques - this technique forms the central form of representation in Chinese-Korean-Japanese ink painting
Light-dark contrast - the method is based on the simple assumption that the shadow is darker than the light ( illuminance ). It is complemented by the setting of explicit lights on raised surfaces.
Cold-warm contrast : The observation of nature has shown the painters that in addition to the illuminance, the lighting color also has a decisive role in the shadow effect, as its interaction with the object color, as well as the different colored reflections from these surfaces, creates a variety of shadow effects. Here, the color tones turn cooler, that is, they become more blue to purple . Therefore, a shadow effect can be achieved through contrasts in the color temperature.
Complementary contrast: From the 15th century onwards, painters depicted shadows by exaggerating the contrasts by using complementary colors. This method can even be used to create shadows in dark areas that normally "drown" into undefined black zones, for example by setting yellow shadows in deep purple. This method, known today as impressionistic, was used by the great fresco painters such as Michelangelo , da Vinci , Sandro Botticelli or Paul Troger on ceiling paintings, in which extreme representations have to be chosen due to the great distance. The Impressionism uses this method again, as Claude Monet .

Examples of shading techniques

The Greek painter Apollodorus of Athens (around 425 BC) is said to have been the first to correctly recognize the different color gradations in light and shadow and to use them to depict depth effects. He is considered the inventor of shadow painting (therefore also called "shadow painter"). The thoughtful rendering of light and shadow was also praised in the works of his pupil Zeuxis . Apollodorus became the founder of perspective painting.
Monochrome painting : grisaille , the black and white painting, in another basic color also called camaieu , in green called Verdaccio . Giotto can be named as a master

Light-dark painting , Italian Chiaroscuro , a painting style of the late renaissance and baroque , which combines the newly developed central perspective with contrasts, or contrasts it as tenebrismo through extreme forms.
This method can later also be found in expressionist film and film noir as low-key lighting ; see lighting design (film)

Illusion painting likes to fall back on the shadow effect of architectural elements ( pseudo-architecture ), for example in the trompe-l'œil or the Lüftlmalerei

the representation of shadows as part of the shading of 3D computer graphics , as used in CAD / CAAD as well as in computer-animated films . This representation is done by the Shader module, which is also implemented in modern graphics engines in the end-user area

Giotto : The Seven Virtues - Iustitia , 1306, fresco; Cappella degli Scrovegni, Padua.
Paul Troger : St. Sebastian and the women , around 1746, oil on canvas; Austrian Baroque Museum
Mock architecture, Salem Imperial Abbey , early 18th century.
Gilles Tran: Glasses 800 edit , still life , POV-Ray , 2006