In four colour printing, images are all made up of halftone dots – one for each of the colours (CMYK). It occurs when 3 or more are all overlaid at angles to create what you can see close up, as a moire pattern, or rosette. Below you can see this represented by Wikipedia with multiple screen angles.
There are 2 kinds of rosette that can be created:
1) Dot Centred
Called dot centered or closed centered, as there’s a dot in the centre!
Details of the dot-centered rosettes are:
• They show a less visible pattern than clear centered ones
• Have individual dots that land on top of one another – reducing chroma/gamut slightly
• Produce colour slightly differently than clear-centered rosettes
• Are more popular with low screen frequencies – 100 lpi and lower
• They tend to lose shadow detail
• Slight mis-registration causes significant colour shift
2) Clear Centered
Clear centered or open centered pattern, as there’s no dot in the centre of this rosette.
Details of the clear-centered rosettes are:
• They show a more visible pattern than dot centered ones
• Look slightly lighter due to more paper showing between dots
• Produce color slightly differently than dot-centered rosettes
• Tend to preserve shadow detail better
• resist color shifts better when slight misregistration occurs
• are more popular with high screen frequencies – 150 lpi and higher
Hope you found that interesting. If you need any more information or want to get in touch, call us on 0844 272 9109 or email [email protected]