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The concept of background color removal and its application in Photoshop

Feb 03, 2019 Leave a message

The concept of background color removal and its application in Photoshop

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   According to the theory of color, yellow, yellow and blue can overprint all the colors of the original, including two series of color and gray (also called non-color). Due to the inherent defects of the inks of the three primary colors, it is difficult to reproduce the neutral gray, and the neutral gray of the corresponding yellow, magenta, and green overprints is replaced by a black ink, which can reduce the thickness of the ink layer on the paper for printing, so In actual printing, a black plate is often added, and the gray portion of the composite color is replaced by black ink, which is called background color removal. If the three-color color ink with the gray component in the composite three colors is removed, and the black ink is replaced, the full-color removal is also called an achromatic structure, and this process saves ink. Dark-adjusted images with dark and dark mixed colors can be removed with a background color.


    In addition, when using PHOTOSHOP software for image conversion, if you use the default settings of the software, you will find that the printed image is not saturated with ink and the color is not bright. This is due to the fact that in the default settings of the software, an achromatic structure is used for the image to be converted, so that the total amount of ink in the deepest is about 280%. In domestic inks, the black ink is not saturated enough to be gray, so that the printed matter printed with such parameters is insufficient in saturation in the dark portion. The total ink limit is set at 400%, which in turn causes the ink to be difficult to dry during the printing process. Therefore, when setting, you need to set the total ink limit to 320-360% and the black ink limit to 80-85%.


In the Ink Options, the Ink Color column lists some types of ink and paper to choose from, and different choices affect color conversion. Printing on coated paper using European standard ink, printing coated paper using American ink, and printing coated paper using Japanese ink are different. The percentage of dots is different. Second. If the outlet is increased, it can be adjusted according to the machine condition of the printing factory. The general value should be between 15-20%.

Here you can enter different values depending on the colour plate and the percentage of the dots.


    The black under the color separation option produces a column that primarily controls where the stencil appears. In printing, the general selection of the  version appears in the middle, ie 30-40%, so select "Medium".


    What needs to be mentioned here is the GCR and UCR in the color separation type. GCR (Gray Color Replacement) is gray replacement.


UCR (Under Color Removal) is the removal of the background color. The use of these two versions will vary. The GCR  version has more successive levels, but the 黒 version appears earlier, so the use of GCR requires the subtraction of some highlights in the image adjustment; UCR is selected, the version is less, but the position is good. Overall, the image layer selected by GCR is more abundant.


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