Lighting as a component of video filming. video art

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Lighting as a component of video filming

video art

It has long been known that improper lighting can make it difficult to recognize the person on the screen. Amateur and professional shots with equally precisely selected compositions often differ in the quality of light.

The range of brightness perceived by the human eye greatly exceeds the range of light sensitivity of any camera, and the image recorded on videotape may differ significantly from what we see. Therefore, we must strive for even lighting of the scene, avoiding excessive contrasts, especially when photographing people.

Lighting requirements increase for frames that are subsequently intended to be used for non-linear editing. When digitizing, quantization noise may appear in large dark areas of the image in the form of chaotically flickering light dots - “snow”, and overexposed areas lose clarity and “spread”.

The situation gets even worse if such frames are further processed by editing programs using all kinds of video effects. For nonlinear video processing, fairly light and smooth (soft) frames, without large monochromatic areas, are more suitable.

In non-directional light reflected, for example, from clouds, ceilings or walls, the image is very soft, without shadows. With scattered (diffuse) light, for example from the sun through clouds or fog, from a lamp with a diffuse screen, the shadows become semi-soft. Narrowly directed sunlight on a clear day or light from a reflector produces deep shadows and hard contrast even when the beam deviates slightly from the optical axis of the lens.

Additional lighting or scattering of light from surrounding objects, clouds or special reflective screens softens the lighting. To eliminate excess light, absorbing screens are used to increase the contrast of certain areas of the image.

Lighting contrast is determined by the ratio of the brightness (in exposure numbers) of the reference gray surface in the light to its brightness in the shadow. Since videos are viewed in daylight, it is not advisable to make the contrast on people’s faces more than 2,5-3, and the brightness ratio of the lightest and darkest areas of the frame should not exceed 30 units.

The degree of contrast in frames gives the scene a certain mood; this property of lighting has been widely used since the dawn of cinematography. The color softens the effect somewhat, but it can always be toned down. A soft image in warm dark colors without drawing details can be used in romantic scenes. Reduced contrast in light colors or a diffused luminous air haze evoke a lyrical mood; they contain an element of some understatement. By increasing contrast and deep shadows, you can emphasize the drama of the moment.

The contrast of the image is affected by the direction of the main light source. The perception of the volume and shape of objects depends to some extent on the direction in which the shadow falls. Frontal lighting (direct light from the side of the camera, for example from the low sun) removes shadows, the texture of objects is almost invisible. With such light it is difficult to convey the depth of the scene; the space becomes flat. People's faces are poorly recognizable. Frontal lighting is only suitable for distant plans where drawing details is not required.

Front-side overhead light (from behind the operator's back from the side and from above) with direction angles from top to bottom and from the side to the lens axis of 30-60° is the most universal, the contrast is moderate, you can photograph people. Side lighting creates dark shadows, emphasizes the volume of objects and the texture of surfaces, and increases contrast. Shadows from objects with a curved shape acquire smooth transitions. Side lighting is suitable for landscape photography. The greatest contrast and three-dimensional effect appears with light perpendicular to the axis of the lens. Counter-side light gives bright highlights on objects, brings lightness and airiness. No details are visible in deep shadows. This light can be used to create a certain mood.

It is advisable to direct backlight (counter) lighting from below so that direct rays do not enter the lens. It gives very deep shadows. The object is depicted by its silhouette. When you select the exposure for the light, a soft halo is formed around the objects, and when you select the exposure for the shadow, a clear light border appears on the outline of the object. Translucent objects glow from within. To photograph shiny and sparkling objects, it is better to direct the oncoming light parallel to their surface. Thus, water ripples or surfaces look beautiful in the low oncoming sun.

Overhead lighting produces short shadows and creates a feeling of heat. The independent use of such light is extremely limited; at least additional front lighting is required.

The emission spectrum of a light source is characterized by its color temperature. Its value is numerically equal to the temperature to which it is necessary to heat an absolutely black body so that it begins to emit light of the same spectral composition as the characterized source. A shift to the red region of the spectrum means a decrease, and a shift to blue means an increase in color temperature. The standard value for white light on television is 6500 °K.

The human eye distinguishes colors well both during the day and under the light of lamps, although objectively the color of objects varies depending on the shade of the light source and the color of the surface. White parts take on the color of the light source, and colored parts change their color in such a way that it is sometimes difficult to predict the result in advance. The brain corrects perception, so even in difficult lighting conditions, we may not notice color distortions.

Measurement of the color temperature of a light source in a video camera is based on a comparison of the intensity of the red and blue components of the emission spectrum. To automatically set the white balance, the parameters of many light sources are stored in the memory of camcorders. But under mixed illumination or illumination by a light source with a discontinuous emission spectrum, errors may appear in the operation of automation, and then white surfaces will no longer be displayed as white on the screen, and a color tint will appear on the entire image.

Even if the white balance is set correctly, the color characteristics of the lighting still change the contrast and saturation of the image. First, surfaces painted in colors opposite to the color shift of the light source appear darker than under white light, their color becomes less saturated. So, under incandescent lamps, the blue and blue parts of objects lose their brightness, and under fluorescent fluorescent lamps (color temperature up to 7500 °K), red, orange and yellow surfaces lose their brightness.

Blueshift lighting makes a person's lips appear almost black and the face becomes overly dramatic. Secondly, surfaces painted in colors similar to the color shift of the light source become lighter on the screen than their surroundings. For this reason, direct illumination with incandescent lamps (color temperature 2500-3200 °K) makes the face of a white person flat and inexpressive, as the lips lighten and "blur".

Publication: video-lighting-notes.blogspot.com

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