Trap (printing)

In printing, a trap, also known as trapping or spread, refers to the intentional overlapping of adjacent colors in a printed design. This technique is employed to compensate for slight misregistration during the printing process. Misregistration occurs when the different color plates used to create a multi-colored image are not perfectly aligned. Without trapping, gaps or white space can appear where colors should meet, resulting in unattractive and unprofessional results.

Trapping aims to eliminate these gaps by slightly expanding the lighter color into the darker color or vice-versa. The choice of which color to spread into the other is usually determined by several factors, including the relative lightness and darkness of the colors, the order in which the colors are printed, and the thickness of the lines being printed. Generally, the lighter color is spread into the darker color because any slight overlap will be less noticeable.

There are different types of trapping, including:

• Choke: A choke is a type of trap where the background color is reduced in size, allowing the foreground color to slightly overlap it. This is often used when the background color is lighter than the foreground color.

• Spread: A spread is a type of trap where the foreground color is expanded to slightly overlap the background color. This is often used when the foreground color is lighter than the background color.

• Automatic Trapping: Modern design and prepress software often includes automatic trapping features that analyze the design and apply trapping rules based on color relationships and object positions. These features can significantly speed up the trapping process.

• Manual Trapping: In situations requiring precise control or when automatic trapping fails to produce acceptable results, trapping can be performed manually by a skilled prepress operator.

Effective trapping is crucial for achieving high-quality print results, especially in complex designs with many colors and fine details. Properly implemented trapping ensures that colors meet seamlessly, resulting in a visually appealing and professionally printed product.