Color reproduction

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The color reproduction is concerned with the reproduction of color images and is a branch of printing technology .

General

Hunt distinguishes 6 cases of color rendering in his standard work mentioned below. Schläpfer summarizes these 6 cases into 4 cases in his book Colorimetry (see below).

Hunt Sleeper
1. spectral 1. spectrally identical
2. colorimetric 2. colorimetrically identical
3. exact 3. Identical in terms of sensation
4. equivalent
5. corresponding
6. preferred 4. Sensitively adjusted

Cases of color rendering

Spectrally identical reproduction

In the printing industry, this can practically only happen if the original is a print itself, as only then is there a chance that the same spectrum of spectral curves will be obtained by choosing identical pigments . This type of reproduction prevents metamerism . This is of great importance when the original and reproduction are viewed together under changing lighting conditions (e.g. reprint of a book or the follow-up volume in a series).

Colorimetrically identical reproduction

The colorimetric measurement values (for example in the CIE-L * a * b * system ) are identical in terms of original and reproduction. The prerequisite is that the color space of the original is not larger than the color space of the rendering system. The term "colorimetrically identical" only refers to one type of light . For colorimetrically identical values ​​under different types of light, the reflectance curves would have to be identical. The samples treated here can therefore be metameric. This type of comparison is important for house colors ( logos ) and for object colors in science.

Sensitively identical reproduction

This describes the best possible reproduction when the color space of the reproduction system is smaller than that of the original. This is important for samples and art (paintings). The color values ​​of the reproduction should correspond to the relative gradation in the original.

Sensitively adapted reproduction

The deviations from the original are tolerated because the viewer already knows the object, for example landscapes or images of people. It depends more on the transport of a mood than on the transport of a color.

Art direction: Impressionism.

This reproduction is also necessary, for example, if a piece of white furniture is to be depicted on white paper in a furniture catalog. If the piece of furniture is lighter than the paper, you would not see it at all with colorimetric reproduction. However, the piece of furniture is printed with a light gray tone, depending on the sensation.

The image editing with image editing programs such as Photoshop always dedicates the maximum brilliance to obtain an image. This is done during image reproduction by compressing the color space ( gamut ) of the original to the color space of the reproduction (if necessary also decompressing), i.e. the lightest point of the original (white point) with white paper and the darkest point of the original (black point) is reproduced with the deepest possible black (usually by printing black with other colors).

Individual evidence

  1. ^ Robert GW Hunt: The Reproduction of Color. 6th edition, Wiley, 2004, ISBN 0-470-02425-9 .
  2. Kurt Schläpfer: Colorimetry in the graphic industry. Ugra, St. Gallen 2002, ISBN 3-9520403-1-2 .

See also