Expert tips for printing gradients

Smoother printed gradients start with the artwork. Use vector gradients where possible, keep color values within a range the print engine can reproduce, and check calibration before changing screening settings. If a job is already at the press, linearization and a different line screen may help reduce visible steps in the fade.

A gradient is a smooth blend from one color to another. It can take different shapes and include more than two colors. Gradients can be difficult to reproduce smoothly, especially in digital printing. The file's construction and the print engine's ability to reproduce small changes in tone both affect the result.

Start at the design stage when you can. A vector element and color values that account for dot gain give the printer a better starting point. When you cannot return to the source document, there are still adjustments to try at the output stage.

Use vector gradients where possible

Raster artwork consists of pixels at a defined resolution, with a color assigned to each pixel. A raster gradient is effectively a picture of a gradient. Its color transitions are already defined before the file reaches the printer, and those transitions may not suit the print engine.

A vector gradient is defined mathematically, with color anchors along its axis. The raster image processor (RIP) can calculate the colors between those anchors. This gives the RIP more flexibility to draw a smooth fade than a raster gradient with predefined pixels. The printed samples below show the difference in this example.

The RIP is part of the path from artwork to printed output. Our print workflow software collection includes RIP and color-management software for readers reviewing that part of their production setup.

Allow for color limits and dot gain

Avoid pushing a gradient all the way to the limits of a color channel when those endpoints cause reproduction problems. As a starting guideline, keep the lowest and highest color values within the center 80% of the channel's full range, as illustrated below. This is a guideline to test on the print engine, not a universal safe range or a guarantee of smooth output.

At the extremes, the artwork may call for tonal differences the printer cannot reproduce. Dot gain can cause tones to merge, often called plugging, and a smooth fade can turn into a visible step or hard line. Figure 3 shows this type of defect.

Check calibration and linearization

When the job is due and you cannot edit the source artwork, begin with calibration. More specifically, check linearization: the process of bringing the print engine's tonal output into line with the requested values. A machine that has drifted out of calibration can show unwanted shifts within small ranges of color.

Keep the printer calibrated and follow its procedure for linearization. If you need help with settings or troubleshooting, use our service and support page to describe the equipment and the problem.

Test a lower line screen or another screening option

If the printer is calibrated and the gradient still shows steps, try a lower line screen if the print engine or RIP allows it. A lower LPI (lines per inch) produces larger dots. This can make the gradient easier for the engine to reproduce smoothly.

Check the rest of the job before accepting that change. A lower line screen can affect other elements, so the improvement in the gradient comes with a tradeoff. Where supported, you can also test another screening option, such as stochastic screening or a line-shaped dot.