Color correction

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Under color correction means the correction or modification of color casts photographic recordings.

causes

When taking pictures, be it photographs , film or television, the color rendering of the product often does not correspond to the expectations of the photographer or cameraman. The causes are often inadequately adapted film material or special lighting conditions on site.

Although these conditions are already taken into account during the recording, be it in the selection of the recording material, through a manual white balance or the use of suitable color filters , there may still be inconsistencies in the result. In this case a color correction must be carried out. This is based on artistic aspects and aspects of human perception . One goal of color correction is a balanced relationship between the color mood to be achieved. The color correction should not be understood as an emergency solution or error correction, but represents a normal work process in the field of photography and film production. This is especially true if the client has strict requirements for certain image elements, because the vehicles or buildings shown are in a clearly defined corporate Design and therefore normal deviations in the color representation must be corrected and idealized.

Color correction for films

When correcting the color of film recordings, which were often shot with different film material under changing lighting conditions, it is necessary to subject all recordings to the adjustment so that the viewer's perception is not disturbed by changing color casts from scene to scene. Although the scenes appear coherent in and of themselves due to the adaptation effects of the eye, the entirety of the cut material must be taken into account during the color correction.

Errors in the recording material and slight differences in the development process can also lead to a different color balance. This work is also known as color or light determination . The analog color correction is already carried out during the copying process in the copier , in which a film is copied onto an unexposed film with a light source. The color spectrum of this light source is decisive for the color balance of the copy. For this reason, the copy light is controlled. The light is influenced either subtractively or additively, which is why a distinction is made between subtractive and additive copying during the copying process .

Subtractive color correction

Here the light is adjusted using correction filters. This method includes the inadequacies of color filters. That means tied up capital in slowly decaying filters, awkward-to-use tax strips made of so-called leatheroid, a type of paper similar to leather, and relatively low copying speed. One advantage is that the light determinators are trained in how to put together the filter sets .

Additive color correction

Three colored light sources - preferably red, green and blue - are used to correct the original, their intensities , or rather the amounts of light, are regulated independently of one another. All parameters and changes over the length of the film must be saved. In the past, this was done using punched tape that ran for the entire duration of the film. In the meantime, however, there are also lighting controls for copier machines in which the values ​​are saved on electronic data carriers and read from there. The advantage here is the purity of the light colors and the rapid change in operation together with the electronic data management.

The profession of color corrector in the film industry is known as a light determiner , in the digital sector as a colorist . They are trained specialists who correct films in specially equipped rooms. The focus Color Analyzer or special purpose computers and special input devices available with which the correction parameters can be very precisely adjusted in real time and stored.

In addition to the technically motivated color correction, it is also possible to subsequently create different moods. In cooperation with the cameraman, a special “look” is often sought for the film. Examples can be found in Steven Soderbergh's films Traffic - Power of the Cartel and Out of Sight , Stanley Kubrick's 2001: A Space Odyssey , Peter Jackson's Lord of the Rings Trilogy , Zhang Yimous Hero and Michelangelo Antonioni's The Red Desert .

Color correction for film and video

In the optical color correction of films, the lighting mood was determined for each setting and saved on punched tape. When copying the film material - controlled by the punched tape - the respective light sources or filters were activated.

With the analog Betacam standard from Sony , a coarse color correction could be carried out by setting the tape bias (made possible by the separately recorded color signal). Rough corrections could be made without the comparatively expensive additional devices.

Since the turn of the millennium, practically all color corrections have been carried out electronically. Optical film material is digitized using a scanner and (for later distribution as film) exposed using a laser.

Nowadays the term color grading or grading for short is usually used for the process of color correction . The alternative job titles Color Grader and Color Timer are derived from this. Since the word "color correction" is associated with the association of eliminating errors, the term grading is better suited to express that the colorist (i.e. the grader) is significantly involved in creating the color moods (looks).

Color corrections when watching TV

Color correction is used not only to correct images, but also to create a mood. In some reality shows, for example, the color is adjusted to give the scene a cheerful touch. On the other hand, in romantic scenes the colors are slightly oversaturated in order to correspond to the cliché of a mountain world. Or the color tone is filtered out and designed to be cool if the scene is supposed to have a negative effect or people are supposed to appear unsympathetic.

Different television standards

When converting video material between different television systems (from the American NTSC to the German PAL system), there are often color deviations which - with professional quality requirements - require color correction.

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