The setting and adjustment of the facial tone in the face must first meet the visual habits of the human eye. A portrait photography photograph, whether it is a smooth light film or a backlight, has a lighter tone in the middle, a lighter, thinner skin tone, a darker tone in the middle tone, darker skin tone, and a dark spot value of 5% or more. It will give people an uncomfortable feeling.
The desktop system scans through A1 and is set automatically. It mainly controls the highlights and dark tone of the tone. Although the two-point control is appropriate, because the depth of the tone density in the original face changes greatly, if no control or adjustment is made, the midtone skin color of the output dot color separation sheet will also fluctuate with the size of the facet density in the original document. In addition, the midtone dots in printing increased more, and the change in skin tone in the middle tone increased. Now many people's face skin color, there is not too bright or too dark, not too yellow or too red and other uncoordinated and unreal defects, it is because there is no good control of the tone.
Table 8-2-1 Interpolation and copy ratio
20 Decrease adjustment when it is reduced by 15
40 Decrease by 10
60 Reduce 5
80 decreases by 3
100 unchanged
600 increase 5 when the zoom is easy to shallow, should be adjusted to increase
1000 increased by 7
1500 increased by 9
2000 increased by 10
The correct control of the middle tone should grasp three relationships and are also three key technologies:
1. The relationship between adjustment adjustment and reproduction ratio
According to domestic research results, when the copy size of the picture is significantly larger or smaller than the size of the original, it is necessary to appropriately correct the middle tone during the platemaking process (see Table 8-2-1). According to Girod's suggestion, the correspondence between the reproduction ratio and the midtone correction value is shown in Table 8-2-2. This is a valuable reference for the scanning and separation of portraits.
Table 8-2-2 Correspondence between copying magnification and midtone correction value
0.20 0.80 1.00 51
0.25 0.80 1.05 52
0.30 0.80 1.10 52
0.35 0.80 1.15 52
0.40 0.80 1.20 53
0.45 0.80 1.25 53
0.50 0.80 1.30 54
2. Correspondence between the density of the intermediate modulation and the value of the network
According to the majority of printing conditions and dot gain rules, the side backlighting and backlighting of most portrait photography photographic originals are dark, and it is necessary to make some adjustments to the midtones to improve the adjustment and determine a constant value of 0.80. The formula for adjusting the density value of the control point is: high optical density value +0.80=medium tone density.
The corresponding relationship between the density value of the medium and the value of the dot network is shown in Table 8-2-2.
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