Lighting and illumination. video art

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Lighting and illumination

video art

As a rule, lighting it can be directed, scattered and combined.

Directional light - this is the light that gives the object pronounced highlights and shadows and in some cases glare.

Scattered light - this is light that evenly and equally illuminates all surfaces of the object, as a result of which there are no shadows, glare and reflections on them.

Combined lighting is a combination of directional and diffused light.

Reducing the overall illumination changes the ratio between the brightness of highlights and shadows: the brightness of highlights decreases faster than shadows. This can be due to some illumination of the shadows with diffused light. Thus, a decrease in overall illumination simultaneously causes a decrease in contrast.

Lighting is simple if the light has one direction, and complex if it comes in several directions, from two or more sources.

Lighting will be hard when the light source is a voltaic arc or an electric lamp without fittings; softened - if it is obscured by a translucent screen (made of paper, milky glass, light fabric), and soft - when it is enclosed in a wide soffit with a translucent screen.

The type of lighting affects the shape of the shadows and the nature of the relief. With hard lighting, the shadow boundaries are very accurately defined, and the relief of the object is exaggerated - one gets the impression that all the depressions have deepened. Soft lighting blurs the contours of shadows and reduces the object's relief. Soft lighting further enhances this effect.

If the light source is close to the illuminated body, then the shadows will be tapered and sharply defined. If two light sources send mutually intersecting rays into space, they will give shadow and penumbra, which soften the contrast of the image.

Rays falling on the surface of an object at an angle of more than 45 ° give direct illumination, and at a smaller angle - oblique.

Oblique lighting emphasizes the shape of objects and brings out their details well. Its variation is sliding illumination, when the angle of incidence on the surface of an object is close to zero degrees. Sliding lighting especially clearly reveals the texture of the object. To soften the contrast in gliding light, additional direct illumination of the subject is given, but from a weaker light source than the gliding light source.

When lighting close-ups with artificial light sources (portraits, still life, etc.), the following are used types of lighting:

Fill or general light - uniform, diffused, shadowless illumination of the object, having sufficient intensity for a short shutter speed. It is carried out by a combination of top and front light sources.
key light - a beam of light directed at an object or its plot-important part. Its task is to create the main lighting effect. Such light should give more illumination in the illuminated area of the object compared to the illumination of the general light. Self-drawing light is rarely used, as it provides contrasting lighting, which makes it difficult to work out details in shadows or highlights due to the large range of brightness.
modeling light - a narrow directional beam of light of low intensity, used to produce highlights that improve the transfer of the volume of an object and highlight shadows in order to soften them, and sometimes completely eliminate them. The purpose of modeling light is to improve the gradation of chiaroscuro. The device for modeling light is a deep narrow soffit with an ordinary incandescent lamp of low power or an ordinary soffit with a tube put on it.
Contour, or backlight, light - back gliding light used to highlight the contour of the object from the background. Such light reveals the shape of the entire object or any part of it. The edge light source is placed behind the object at a close distance from it. A thin line of the light contour is obtained, which expands with the removal of the light source from the object. As a device for contour light, a soffit with an average reflector diameter is used.
Background light - light that illuminates the background against which the object is projected. The illumination of the background should be less than the illumination given by the general and key light. Background light is uniform and uneven. Usually it is distributed so that the light parts of the object are drawn on a dark background, and the dark parts on a light one. For uniform illumination of the background, light sources are used in a wide soffit, and to create light spots on it, in a narrow soffit. Excellent light softening results are obtained by reflected light, for this purpose umbrellas with a reflective surface and flat reflectors made of white fabric on a frame are used.

Illumination - this is a physical quantity that characterizes the illumination of the surface, created by the luminous flux incident on the surface.

The unit of illumination in the SI system is the lux (1 lux = 1 lumen per square meter), in the CGS - phot (one ph is equal to 10000 lux).

Unlike illuminance, the expression of the amount of light reflected by a surface is called luminance.

Illuminance is directly proportional to the light intensity of the light source. As it moves away from the illuminated surface, its illumination decreases inversely with the square of the distance.

When the rays of light fall obliquely to the illuminated surface, the illumination decreases in proportion to the cosine of the angle of incidence of the rays.

For example:

illumination by sunlight at noon 100 lux;
when filming in a studio 10 lux;
outdoors on a cloudy day 1000 lux;
in a bright room near a window 100 lux;
on the desktop for fine work 100-200 lux;
necessary for reading 30-50 lux;
on the cinema screen 85-120 lux;
from the full moon 0,2 lux;
from the night sky on a moonless night 0,0003 lux.

Publication: video-lighting-notes.blogspot.com

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