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| Understanding Color/Color reproduction | Index | Home |
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Halftone (halftone screen), dot gain, Moiré effect |
In printing, shades of color are reproduced by tiny dots called halftones. Dots printed using the CMYK plates are allowed to overlap to reproduce an image. In order to create the dots, a fine mesh screen is used to photograph the image, which results in an image composed of dots of varying sizes. In digital halftone processing, a single dot is comprised of numerous small dots. |
A side effect of the screening process is that dots become too dense in the middle portion (approximately 50%) of the image. This is called dot gain. This can be prevented by increasing the light in the middle portion of the image prior to screening. |
All printing plate images are made of dots, and if they are allowed to overlap as is, they will create an interference pattern called moiré. In order to prevent this, each plate is rotated slightly. Moiré patterns also might appear if the plates are set at improper angles, or if the photographic subject itself contains a regular pattern, such as checkered textiles or a tile-covered building wall. |
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