At a color separation objects which partially superimpose each other, can be arranged on color-splitted bands by following methods.
|
Color of the upper object is surprinted (overprint) in the field of overlapping on color of the lower object without removal last (look the previous section). |
|
Color of the lower object in the field of overlapping can be deleted (knockout). |
The first variant is peculiar only for the press плашечными colors when each color is printed special смесевой by color.
And the second variant is characteristic for printing by triad colors (blue, magenta, yellow and black) which, being the put small points, at physical and optical superimposing form diversity of color.
For color плашечной the press the great value has accuracy of superimposing of prints of various color in the led out boundaries — so-called ' приводка "(registration). At adjoining objects of different color incorrect приводка creates the empty not sealed gaps, on the one hand, and unreasonable"нахлесты"— with another.
In practice of polygraphic processes it is possible to reduce considerably possibility incorrect приводки, but to bring it to naught it is unreal, the technology треппинга (trapping) — small magnification or reduction of the area of object to compensate shift during printing of printing forms rather each other (fig. 16.6) therefore is developed.
In Adobe Illustrator program following methods of creation треппинга are used.
|
By means of button Trap (Треппинг) palettes Pathfinder (Handling of circuits) it is fulfilled automatic треппинг for the image consisting of simple objects. This method is not intended for such difficult objects, as the graded-index and decorative filling, the imported pointwise drawing. The information look further in section "Button Trap" of this chapter. |
|
Треппинг forms at the expense of change of a thickness of a circuit of separate objects by means of palettes Stroke (Line). About it look more low in section "Obtaining треппинга by means of superimposing" the given chapter. |
 |
| Rice 16.6. The press without треппинга and with usage треппинга (in a central picture the circle extension, sufficient for error compensating приводки is shown) |
If objects which are superimposed against each other, have the general colors for such objects треппинг most likely it is not required. For example, the first object contains 30 % of magenta and 90 % yellow (the pleasant it is light-ohristyj color), and the second object — 60 % of magenta and 20 % black (not less pleasant violet color) in between not sealed space cannot appear, at the worst can appear a magenta gap as magenta color is the general for both objects.
 |
| Rice 16.7. Exterior треппинг (the smaller object extends) and internal треппинг (it is narrowed down больший object) |
If colors of adjacent objects absolutely different it is required треппинг which happens two types (fig. 16.7).
|
Exterior треппинг (spread) which expands boundaries of light object against a dark background for support of small overlapping. |
|
Internal треппинг (choke) which moves boundaries of a light background in dark object for creation of small overlapping. |
To fulfill треппинг follows at the most final stage as any transformations will influence value треппинга (for example, object scaling causes proportional change and for value треппинга) that, certainly, it is undesirable.
At application треппинга in a case superimposing of two light objects in the field of superimposing more dark boundary or boundary of other contrast color that does not enter at all into intentions of the designer can be formed. For example, light yellow and light blue objects can треппинга form a bright green band in area.
For preventing of it it is necessary to reduce percentage of color in area треппинга (in the given example — yellow color), beforehand consulted with experts of the polygraphic enterprise.
Треппинг a font
The font placed within images, represents the considerable difficulty for the press. Especially attentively it is necessary to concern a small size.
It is necessary to avoid layout of a small size in images which are exposed to rasterization.
Треппинг a small print in плашечной the press at the slightest error приводки also creates the unreadable text. If the font of dark color is printed on a color background it is necessary to prefer overprinting (overprint). The simple decision in this situation is more effective.
If the type size exceeds a certain limit it is possible to fulfill треппинг a font, placing its copy under the original and increasing a thickness of a circuit by certain value.
Eventually, the font by means of command Create Outline (to Transform to circuits) can be converted menu Type (Text) in curves and to apply to it треппинг, as to any graphic object. Certainly, possibility of editing of the given object as text, and also advantage of a font will be thus lost at rasterization which are provided to it with technology хинтования (hinting).
Button Trap
By means of button Trap (Треппинг) palettes Pathfinder (Handling of circuits) which is caused on the screen by command Show Pathfinder (to Show handling of circuits) menu Window (Window), it is possible to fulfill automatic треппинг simple objects. Function consists that the program finds Light objects in the image, irrespective of their layout (in image quality or a background), and applies to them the installed parameters треппинга.
If two superimposed objects appear light color, the program uses малейшее'отличие in color to prefer one of objects. If program "decision" not seems to the user satisfactory, by means of flag Reverse Traps (Inverse треппмнг) in dialog box Pathfinder Trap (Handling of circuits: Треппинг) it is possible to change a direction треппинга.
For performance треппинга it is necessary to select two or more objects and to click on button Trap (Треппинг), the program displays dialog box PathlMer Trap Handling of circuits: Треппинг) (fig. 16.8).
 |
| Rice 16.8. Button Trap and dialogue oкно Pathfinder Trap |
|
In the field Thickness (Thickness) is set value треппинга in a range from 0,01 to 5000 points. Value should be coordinated it with experts of printing house. |
|
Field Height/Width (Height/width) serves for ratio determination треппийга but verticals and across. Setting of the given value can be caused necessity to compensate, for example, a non-uniform stretching of a paper across and on a vertical in the course of the press. Зйачение it should be coordinated with experts of printing house. Value by default 100 % assumes identical value треппинга in both directions. To increase треппинг across, it is necessary to install Value of more than 100 % (but no more than 400 %) and to reduce — value of less than 100 % (but not less than 25 %). |
|
In the field Tint Reduction (Clarification) it is possible to install value which provides change of a color shade of area треппинга, applied to light object. Value of 40 % by default is accepted. |
|
Flag Traps with Process Color (composite colors) provides with Trepping color hue converting in area треппинга in an equivalent of triad color (in parameters of color model CMYK), It should promote предотвращений appearances of another плашечного colors at a color separation. |
|
Flag Reverse Traps (Inverse треппинг) provides direction change треппинга (not at more light, and at more dark). This function is not spread to objects with so-called "saturated black" (Rich Black) — the color containing besides black any an amount of blue, magenta and yellow colors. |
|
Button Defaults (By default) allows to recover the values accepted by default. |
If more exact is required control треппингом, than it allows button Trap (Треппинг), or треппинг difficult objects it is possible to fulfill треппинг, changing parameters обводки objects.
For this purpose it is necessary to select the upper object from what should "participate" in треппинге, and then by means of command Show Stroke (to Show a line) menu Window (Window) to cause on the screen palette Stroke (Line) with which help it is possible to simulate треппинг.
To create exterior треппинг (spread), it is necessary to appropriate обводке the same parameters of color, as at object filling, and also to increase/thickness обводки.
To create internal треппинг (choke), it is necessary to appropriate обводке the same parameters of color which the background object has, in this case at object color parameters обводки and filling will be various.
In the field Weight (Thickness) it is necessary to install value of a thickness обводки, ¦ in a range from 0,6 to 2,0 points, considering that обводка in the thickness 1 blows „I creates value треппинга half this value. Exact value j треппинга follows согласовать'со experts of printing house.
Then it is necessary to activate palette Attributes (Attributes) and to install i flag Overprint Stroke (line Superimposing) that provides in exterior in, internal треппингах the press with superimposing in the specified areas.
To create треппинг at обводки, it is necessary to select I correspond - щий object, then in palette Stroke (Line) to appropriate обводке white color and to install a necessary thickness. By means of command Copy to (Copy) menu Edit (Editing) it is necessary to copy a circuit in a clipboard, and then to execute command Paste in Front (to Paste forward) menu Edit (Editing). Ксщия a circuit it will be placed over the original and it is selected.
By means of palettes Stroke (Line) it is necessary to appropriate necessary color and a thickness, and a thickness should be more former on value idle talk-pjnga. Then it is necessary to activate palette Attributes (Attributes) and to install flag Overprint Stroke (line Superimposing).
To fulfill треппинг not at all object but only at its part, it is necessary to arrive as follows: to create a new circuit along a line assumed треппинга, and then to fulfill the same operations, as in the previous case.