Banding gradient in printing
One of the most common issues encountered in quality control and printing of gradient-filled areas is gradient banding. This manifests as visible bands, sharp color transitions, and striations within the gradient, often resulting from neglecting the appropriate choice of print resolution during the lithography process, file resolution during design, or even the gradient's design and application. This issue must be addressed before printing, during the design or lithography output phase, as correcting this error during the printing process is generally not feasible.
Gradients are a versatile technique in image creation, adding depth and visual appeal. This process begins with two or more color stops. Each color stop can have its own specific definition within the CMYK color system. Gradients typically appear very smooth, attractive, and free of banding or striations on monitors. Therefore, it's crucial to remember that monitor displays are not a reliable indicator of how the file will print.
When discussing error checking or file inspection, it's crucial to remember that monitors are not equipped to reveal all potential colorimetric or prepress errors. Even professional design monitors with the best calibration processes may not fully expose certain issues such as color shifts, overprint errors in Pantone colors, and other nuances. Therefore, it is essential to perform thorough prepress checks to ensure the final printed output meets the desired quality standards.
Banding control in design
When using gradients, at least two color stops must be created. The closer these two colors are to each other, the higher the probability of errors during lithography and printing. It's important to remember that lithography, in the process of creating halftones, cannot instruct gradients to improve or smooth the transition between colors.
Color corrections should primarily be made by the graphic designer. The farther apart the two color stops are, the smoother and better the final result. While this is the first step, other key points must also be implemented to prevent banding.
If you are using multiple color stops, the same rule applies. A maximum distance between each pair of stops can help improve the print quality of the product. For this reason, using more than three color stops in a gradient is generally not recommended as it becomes difficult to maintain a suitable distance between them.
Banding in resolution
Sometimes, it's necessary to use gradients for pixel-based images in Photoshop. In such cases, the file resolution can introduce errors. Contrary to what many designers believe, increasing the resolution in PPI units not only fails to improve print quality but can actually increase the likelihood of errors. Higher resolutions require better materials and more attention to production.
As the resolution increases, the rip in lithography requires more color processing, which can lead to banding in gradients. The best approach is to choose a file resolution appropriate for the quality factor of 2, considering the LPI (lines per inch) specified by the lithographer.
If you are forced to use a high resolution in lithography and, consequently, in your file, you can either reduce the number of gradient steps or apply filters like "Add Noise" to make minor adjustments to the image to improve print quality and reduce gradient banding.
Banding in lithography
As discussed in previous points, lithography, due to the power of the laser, microdot structure, materials, and the type of printing machine, can select a suitable resolution in LPI for halftoning. When using a high resolution, the dots become smaller, and the production process requires greater precision. The smaller the dots, the more difficult it becomes to control them in gradients.
Therefore, it is highly recommended to use a normal LPI when gradients play a key role in the design. By reducing the resolution, the halftones will be larger, and the space between two color stops is easily filled, allowing the ink to better cover the colors. A quality factor of 2 is sufficient for creating a file resolution relative to LPI. For this reason, even in fine art works with many gradients, 150 LPI is often recommended over other units like 175 LPI to prevent gradient banding.
Keep in mind...
that there may be different terms and meanings used in troubleshooting and preflight. For example, the term 'banding' can refer to both gradient banding when using gradients and printing banding, which is also known as gear marking. Therefore, if you encounter these issues while monitoring printing and troubleshooting, first search for the correct meaning of the error and address it accordingly based on its type.
