Prepress Made Simple: A MegaColorUSA Guide to Better Print Files

What is prepress?

Prepress is the preparation that happens between creating your artwork and producing the finished printed piece. It is the quality-control stage of printing—making sure images, colors, dimensions, bleeds, fonts, and other details are prepared correctly so the press can reproduce the design as intended.

PPI and DPI

PPI, or pixels per inch, describes the resolution of a digital image. DPI, or dots per inch, refers to the resolution of an output device such as a printer. Whenever possible, use the highest-quality original images.

CMYK, halftones, and color separations

Tiny dots of cyan, magenta, yellow, and black ink work together to reproduce full-color images. A full-color image is separated into individual ink plates, and halftone screening varies dot size to create tones, shadows, and gradients.

Spot color

A spot color uses a premixed ink instead of a CMYK combination. It is useful for exact brand colors and specialty effects and can print at full strength or as lighter tints.

Knockout, overprint, registration, and trapping

A knockout removes the color beneath an object; overprint places the top color over the color below. Printing is in register when colors align correctly. Trapping adds a very small overlap between adjoining colors to prevent white gaps caused by slight movement on press.

Other useful terms

Dot gain is the natural enlargement of halftone dots on paper. A moiré pattern is an unwanted repeating pattern caused by conflicting screen angles. A RIP converts digital artwork into the data the printer understands. A PDF is not automatically print-ready—size, resolution, color, bleed, fonts, overprints, and layout must still be checked.

MegaColorUSA tip: A few minutes spent checking artwork before submission can save time, revisions, and headaches later.