Trapping – overlay

 

Ulrichs repetition:

Illustrator:  Man tegner en fisk – expander den

 

new schwatches – spotcolor –

 

fiskekropsform og haleform lægges  oveni hinanden med spotcolors

 

klik på seperation og tjek at det er cmyk

 

pasningsmærker skal være i registrationfarve

lav trap-overlay med ……. og sæt den på 1.8 pt

 

sidder default til offset

 

sættes til pdf (adobe pdf)

output som separation (to farver)

 


Fra Wikipedia:

Trapping Directions 

It is important to know that the darker color always keeps its shape. The neutral density of a color is used to determine its darkness.[2]
The lighter color can trap the darker color in the following directions:

  • Choke: The yellow square makes the cyan circle in the middle smaller.

Choke

  • Spread: The yellow circle becomes bigger.

Spread

  • Centerline: Both Spread and Choke are applied (rarely used).

Centerline

Trapping decision making

Certain basic rules must be observed.

First, the decision should be made as to whether a trap is needed between two specific inks, in other words, if these two abutting colors are printed, is there a risk of gaps showing up when misregistration happens?

In case the two colors in question are spot colors, trapping is always needed: from the moment the artwork is imaged on film or plate, they are handled separately and ultimately will be printed on two different printing units. The same applies if one of the colors is a spot color and the other a process color.

The decision becomes a bit more tricky if the two colors are process colors and will each be printed as a combination of the basic printing colors Cyan, Magenta, Yellow, and Black. In this case, the decision as to whether to trap or not will be defined by the amount of ‘common’ color.

Another factor that will influence the visibility of the traps is the direction of the trap. The decision as to which color should be spread or choked is usually decided upon the relative luminance of the colors in question. The ‘lighter’ color should always be spread into the darker. Again this reflects the way the human eye perceives color: since the darker colors define the shapes we see, distortion of the lighter color will result in less visible distortion overall. The ‘lightness’ or ‘darkness’ of a color is usually defined as its ‘neutral density’.

A major exception to this rule should be applied when opaque spot colors are used. Other colors, regardless of the relative luminance, should always be trapped (to spread under) these spot colors. If several of these spot colors are used (a common practice in the packaging market), it is not the luminance of the color but the order of printing that will be the decisive element: the first color to be printed should always spread under the next color.