Brighten human skin

The technology applied to TV cameras surprises us day by day with its evolution, and even more so if we compare it with that of the old tube cameras. Today's equipment can handle contrast ranges of up to 30:1, much higher than the cameras of a few years ago. This means that it is possible to record good quality images in which the lighter part emits up to thirty times more light than the darkest part.

When illuminating a set, not only the color of the panels and the relationship of the contrast between the walls and the props should be taken into account. We must also consider the color of the skin of actors and presenters, which often corresponds to intermediate tones that can be lost due to inadequate lighting.

Getting a good contrast range is just as important as maintaining the midtones. As in black and white photography, the television director must take advantage of the technical resources at his disposal to generate images with a complete range of grays, which are pleasing to the eye and deliver the maximum of information in each shot.

When talking about contrast, we must mention brightness, that is, the ability of an object to reflect the light it receives in a certain direction. Video cameras record brightness variations as changes in the luminance of the video signal, which are directly related to the amount of light that reaches the focal plane through the optical system.

It is possible to measure the brightness of an object using conventional photometry instruments, which can become a valuable aid to the television illuminator. There are two types of brightness: that which originates directly from a light source, and that which is perceived by the reflection of light on the surface of an object.

The brightness of natural light sources will almost always generate images that exceed the contrast range that a video camera can handle. In almost all cases, the lighting work must be carried out based on the brightness variations of the objects found in the set, taking into account that the reflection of light is directly proportional to the intensity of the source and inversely proportional to the surface.

Although it is possible to make adjustments of intensity, concentration and aperture in conventional lighting instruments, the perceived brightness also depends on the angle of incidence of light on the surface of objects. Positioning a lamp at too close an angle can produce excess brightness that makes it impossible to capture detailed, good-quality images.

The correct angle to place luminaires in the studio is between 45° and 60°, a position that ensures good coverage and minimizes the possibility of generating points of excessive brightness. An angle below 30° can lead to problems with glare, excessive brightness and exaggerated increase in contrast with loss of detail in the middle tones.

In short, it is about preventing the incident light from being reflected perpendicular to the focal plane of the camera, preserving the concentration characteristic of the original light sources.

Human skin reflects a limited amount of light, more or less constant in each particular case, but its organic characteristics – such as sweat, fat concentration and variations in hue – can cause untimely changes in brightness, which often become a serious lighting problem.

Sometimes we manage the set according to our sight and forget that we are not working for theater, but for television. Our real answer is the image that the cameras give us.

Today's cameras can accept pure white, and even take shots in front of a reflector, without this action harming them. CCD elements allow images of acceptable quality to be obtained from illuminated sets with excessive contrast, even with hot spots or glare points. Even so, the use of pure white in the scenography is still a big problem for the filmmakers, since the contrast ratio of the video is still limited and it is difficult to obtain correct skin colors when the cameras are pushed to the limits of their performance.

To objectively evaluate the image quality and light response on the set, and in front of the cameras, we have to help ourselves with the vectorscope and the waveform monitor. The illuminator must use these tools to establish references that allow it to maintain constant luminance values in the different shots.

If a standard value is set for skin luminance, it is relatively easy to adjust the lights to enrich the tone range of an image by increasing contrast.

By exceeding the contrast range of the camera, the faces begin to darken. Technicians tend to startle and start adjusting the electronic controls of the cameras, trying to alter their response to improve the image.

But electronic means are not enough to control these situations, because even if the levels are lowered or raised, the contrast ratio is preserved. Then it is necessary to apply lighting techniques to attenuate the light of the set – especially the anchoring – and give an acceptable light level in people, in order to balance first terms, subjects and set.

What is recommended for use of white on TV is a gradient tone with a maximum of 70% reflection, light grays that give the feeling of white without overshadowing other elements of the image.

It is also common to find that the color of the set is very similar to that of human skin. In these cases it is advisable to break the background color by casting shadows with stencils or gobos, decrease the intensity of the incident light on the panels or change the color of the light using gelatin filters.

The use of these techniques, with the help of separation lights or backlights, allows to "take off" from the background to the subject and obtain a clear perception of three-dimensional space in the image.

Facial wrinkles, acne and other marks – including dark circles and other signs of fatigue – require light treatment with color filters, in order to make up the face through light. This technique can complement facial makeup and improve the image of the subject, saving time in production.

Makeup filters, on the other hand, respond to the color of the skin and its degree of absorption and reflection of light. The skin reflects a maximum of 41% and at least 28% of the incident light. Very white people appear on video with a very pale face, without color, while the darkest tend to appear too dark, without contrast or expression.

As the case may be, the illuminator selects the appropriate filters, which usually allow the light to be colored very lightly, to better delimit the dark areas or add some dye to the lighter parts.

On the other hand, the selective use of color filters can be used for cases where it is necessary to combine different skin tones in the same plane. It is usually necessary to handle colored lights on the backlights, to get more definition when the subject has a dark complexion. These lights should be applied in a timely manner to avoid altering the overall appearance of the frame.

In addition to the cosmetic use of color lights, the quality and concentration of light can be manipulated for dramatic effect. Hard lights – provided by fresnell reflectors – mark strong features and highlight facial defects. Diffuser filters distribute light, attenuate hard features and skin imperfections, and project facial smoothness to the cameras.

In case of emergency, if you do not have professional filters for lighting, you can use as a resource the translucent paper used by draftsmen, with the thickness that is convenient.

Beyond purely optical resources to control light, the most modern digital cameras have digital signal processing functions that allow you to control color in vector form or reduce the detail of any of the color components.

The use of these tools can become a valuable aid for the television illuminator, who thus manages to use these means to optimize his control over the image and bring his work even closer to that of the painter.

However, we must not forget that, although the camera is a liar, it is difficult to obtain better images than those that are put in front of it...