Halftone software screen printing

Under the hood SimRip starts by creating a new output document at the resolution set in the options dialog. Each channel in the document is then converted to high resolution bitmap, while retaining the original color values and channel settings. Ready to Print Channels generated by the SimRip script can be printed directly onto film using an Inkjet printer, and used for making high quality halftone screens. Output files generated by SimRip are already halftones, so they can be printed as separations using any Driver or Rip.

Dot Size and Angle Customize the dot size and angle for each channel in the main dialog. Conventional screening, for offset and flexo presses, breaks a continuous tone black and white image into a series of dots of varying sizes and places these dots in a rigid grid pattern.

Most inkjet presses can print even single dots on their own and produce a fairly uniform tone from them. They can therefore use dispersed screens, sometimes called FM or stochastic halftones. A dispersed screen uses dots that are all more or less the same size, but the distance between them is varied to give lighter or darker tones. Dispersed screening can retain more detail and tonal subtlety than conventional screening can at the same resolution.

This makes such screens particularly relevant to single-pass inkjet presses, which tend to have lower resolutions than the imaging methods used on, say, offset lithography. Flamenco, Rosette and Interlocking. Each of these methods have been developed to use halftone screens with color ink to simulate continuous tone color images and graphics through the halftone printing process. Flamenco is a color halftone printing method which prints all the halftone dots at the same LPI and Angle.

In short it is a form of dot on dot halftone color printing. The above image simulates a simple red to yellow color gradient with flamenco halftone printing.

When comparing the actual color gradient, the 3rd image to the right against the flamenco simulation on far right we can see the gradient blend of red to yellow is not a very good reproduction of the gradient. This is due to dot on dot halftone printing. Which results in one halftone color stepping on the other and effecting the color and gradient results.

You will also notice the much of the orange in the gradient is entirely missing. Resulting in the color simulation of the gradient being inaccurate.

In short printing dots side by side with some dot over lapping. The above image simulates a red to yellow color gradient with rosette halftone printing. Comparing the actual color gradient in the middle with the halftone rosette simulation on the far left, once again we see the gradient is not accurate. The color blending and gradient throw orange is smoother than flamenco but sill much of orange simulation is incorrect.

Interlocking halftone printing is the best practice for CWB simulate process color screen printing. Interlocking halftone printing prints inverted halftone dots next to regular halftone dots.

The interlocking halftones then print side by side and the dot do not allow one color to be printed on top off or step on the other color. The result is highly accurate gradient blending and color simulation when compared to flamenco or rosette halftone printing for simulated process color screen printing.

The above image simulates a red to yellow gradient with interlocking halftone printing. With interlocking the halftone dots do go over or overlap, they are side by side without any over dot lapping or color stepping on color.

If you compare the original color gradient the 3rd image to the right with the interlocking halftone image the final image to the right. You will notice that the color gradient is highly accurate and the orange color simulation from the red and yellow combined is also very accurate.