Go dorsum inward the history of halftoning in addition to you'll notice that for multi-color presswork the halftone screens were ever angled relative to 1 another. Why non simply convey all the screens at the same angle in addition to live on done alongside it? Well, when halftone dots are at the same frequency in addition to angle in addition to so they volition either impress on travel yesteryear of each other (dot on dot)
or they volition impress partially overlapping
or they volition impress beside each other (dot off dot).
When dots impress on travel yesteryear of dots yous convey moisture ink sticking to moisture ink (wet trapping) in addition to white spaces betwixt the dots. When dots impress beside dots yous convey moisture ink sticking to dry out newspaper (dry trapping) alongside less white spaces betwixt the dots. What does that mean? If yous await at the images inward a higher house you'll run into that the dot on dot color looks darker in addition to less vibrant than the dot off dot. The resultant is that the in conclusion blueish hue, inward this example, of dot on dot volition likewise live on dissimilar than the dot off dot blueish because moisture trapping inks reduces the ink's efficiency at filtering light. The white newspaper surrounding the dots likewise contaminates the perceived color yesteryear adding a graying outcome in addition to thence the dot on dot printing volition convey less chroma (vibrancy) than the dot off dot.
The biggest number though is that when at that spot is slight misregistration on press the covert volition shift from dot on dot to dot off dot causing the presswork to shift color in addition to note dramatically. However, yesteryear rotating the screens relative to 1 another, this moisture trap/dry trap outcome is randomized in addition to thence the color becomes to a greater extent than consistent when slight misregistration occurs.
The mo major number that occurs if all the screens inward an AM/XM halftone convey the same angle is that of moiré. Here, 1 of the colors has been slightly rotated - peradventure because of a modest imaging problem, or because of a modest press problem.
When this happens a really rigid moiré appears when all colors convey the same angle. However, yesteryear rotating the screens so that they are thirty degrees apart, at that spot is to a greater extent than or less tolerance for modest angle errors in addition to moiré volition non appear.
Using rotated covert angles for AM/XM halftones overcomes the dot on dot/dot off dot issues.
With FM/Stochastic screening, the same problems are overcome yesteryear using a dissimilar covert designing for each of the procedure colors.
or they volition impress partially overlapping
or they volition impress beside each other (dot off dot).
When dots impress on travel yesteryear of dots yous convey moisture ink sticking to moisture ink (wet trapping) in addition to white spaces betwixt the dots. When dots impress beside dots yous convey moisture ink sticking to dry out newspaper (dry trapping) alongside less white spaces betwixt the dots. What does that mean? If yous await at the images inward a higher house you'll run into that the dot on dot color looks darker in addition to less vibrant than the dot off dot. The resultant is that the in conclusion blueish hue, inward this example, of dot on dot volition likewise live on dissimilar than the dot off dot blueish because moisture trapping inks reduces the ink's efficiency at filtering light. The white newspaper surrounding the dots likewise contaminates the perceived color yesteryear adding a graying outcome in addition to thence the dot on dot printing volition convey less chroma (vibrancy) than the dot off dot.
The biggest number though is that when at that spot is slight misregistration on press the covert volition shift from dot on dot to dot off dot causing the presswork to shift color in addition to note dramatically. However, yesteryear rotating the screens relative to 1 another, this moisture trap/dry trap outcome is randomized in addition to thence the color becomes to a greater extent than consistent when slight misregistration occurs.
The mo major number that occurs if all the screens inward an AM/XM halftone convey the same angle is that of moiré. Here, 1 of the colors has been slightly rotated - peradventure because of a modest imaging problem, or because of a modest press problem.
When this happens a really rigid moiré appears when all colors convey the same angle. However, yesteryear rotating the screens so that they are thirty degrees apart, at that spot is to a greater extent than or less tolerance for modest angle errors in addition to moiré volition non appear.
Using rotated covert angles for AM/XM halftones overcomes the dot on dot/dot off dot issues.
With FM/Stochastic screening, the same problems are overcome yesteryear using a dissimilar covert designing for each of the procedure colors.
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