Comparison of halftone images

Continuously tuned images, such as photographs, are often printed using a traditional method called halftone screening. This method is now done by the computer. Continuously tuned images are scanned and digitized into many colored pixels. The more pixels per inch (ppi), the higher the image accuracy. During printing, the pixels are processed by a raster processor (RIP) to form an array line of dots with different sizes and densities of four colors CMYK.
This grid, also known as a halftone screen, can make the eye mistaken for seeing continuous tone images. Increased dots per inch (dPi) and lines per inch (Lpi) increase image clarity. In order to avoid the occurrence of erroneous piebald spots, each color screen line is rotated through a certain angle for printing so that weave patterns form a rose pattern. For a long time, rose pattern is the basis for printing continuous tone images on paper.

Halftone for digital printing One of the advantages of digital printing is that halftones are printed directly onto paper, with no intermediate transitions. In the traditional plate making process, the dots produced by the laser imagesetter lose the accuracy in the process of making films, plates, and inks.
In digital printing, the plate or photoconductor is directly imaged to form dots. The toner is adsorbed onto the paper with substantially no dot overflow. Unlike traditional offset printing, some digital printing can also change the amount of ink or toner per dot. This technique is called "variable dot density." This technique can show subtle gradation and color gradation changes, greatly improving the clarity of the image.
Digital printing has a variety of screening methods such as rose pattern. Based on the special calculation method in RIP, some digital printing can also achieve non-traditional screening. These screening methods are more suitable for some specific images. Since most plates and cylinders are electronically controlled in digital printing, operators can easily adjust screen parameters and dot density as needed.
In summary, digital printing can print 600-2400 dpi and 133-175 Lpi halftone prints under different printing presses and screening methods. The variable dot density can further increase the image resolution. Moreover, digital printed images are brighter because the toner is not absorbed by the paper. The use of embossing rollers or cover film enables digital prints to have the gloss effect of offset inks. In addition, digital printing also allows the printing range to adjust the color range and screening method.