To make a halftone from a full-color or grayscale image, open PHOTO-PAINT and open an image. Go to Image>Convert to Black and White. The next window opens, and a couple of decisions need to be made regarding the screen type options: the number of lines per inch (LPI), round versus square dots, and the angle direction.
If you want to create the illusion that the dots are creating a gradient or lighter tone of a single, continuous color, and the item is going to be viewed at a distance less than two feet (the distance at which a magazine or newspaper would read), use an LPI at 150 to 300. If you want larger dots created for an exaggerated effect, use a number below 30. Once the image has been converted to a halftone, save it as a BMP file (bitmap).
—9th Street Designs