Two serious errors that occur while changing printing quality - Part 2

In the first part, i talked a little about Moire texture and here I want to examine the factors that cause it. The Moire texture occurs even though it is something unpleasant to the eye. All that lithographs and designers want is to find a way to maintain the quality of the final print when they change pictures and vectors into Halftones or Dots. One of the first steps to get there is to control the Moire texture. Here are some reasons why a Moire texture would develop:

1- Scanning/Sampling Moire

When you want to scan a photo or take a picture, there are many natural textures on the image, leading to the development of Moire. Usually, stripes placed in close intervals on the clothes may create a visual illusion. Of course, there is not always a solution for these pictures; for instance, imagine you want to layout a brochure from a photo taken from a surface of a tie. Moire will probably happen since the problem goes back to when you took the picture or scanned it.

To reduce Moire, taking a picture with a different resolution or a slight change of the camera's angle would be a good idea.

2- Screening Moire

Screening is when you change the file into some Dots so that the printer can read and operate them. As mentioned above, every color is a matrix of Dots, which is placed at a specific angle from the other color to create the visual illusion of a consistent image. If the angle of the Dots does not apply to the printer during the printing or lithography, Screening Moire will occur, and our eyes may catch a glimpse of the crimp on it.

To solve this issue, you have to make sure the angles created in lithography are based on required standards.

3- Resampling Moire

Just like when you try to take or scan a photo, you may import a picture with close stripes into Adobe Photoshop. If you increase the resolution of the picture, the possibility of Moire's occurrence around the stripes is high.

To fix the problem, use Blur filters to reduce the Moire. Not every situation can be dealt with this easily. Moire may occur even by changing the size of a picture.

4- Demosaicing Moire

Sometimes when you want to layout, you need to use small-sized and low-resolution images. When you change the resolution of an image, the PPI density will change, and thus the stripes will not blend in with the new PPI; therefore, the Moire occurs. In Resampling Moire, the error occurs when you increase the resolution; however, in Demoseicing Moire the error occurs due to resizing the image and increasing the resolution.

The solution to this issue is to use bigger original pictures.

5- Single Channel Moire

As mentioned in part 1, to create a visual illusion of harmony of the Dots, some Dots are arranged at a specific angle next to each other. There are times when these angles are reduced from another color's angles, which will lead to an error called Screening Moire. Sometimes, the standard-setting of the angles must be changed unless Moire happens.

For instance, in Flexographic printing, the Dots have a 7.5 tilt angle to prevent the occurrence of the Single Channel Moire.

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To be countinued...