Graduated screens (sometimes known as gradations or blends) can add interest to your print project, but they are not always practical for all situations. Graduated screens need room to blend smoothly and evenly. When the blends are created in too short an area, they will form hard lines commonly known as “bands”.
Adjustments can be made by decreasing the percentages of the start and finish points, or by expanding the area where the blend is to be placed. Example: In a 8 ½” wide x 2″ high bar where the screen is graduating top to bottom (the 2″ way), the blend should NOT be set to go from 100 to 3%. Instead, it may be better to go from 50 to 3%. Another alternative would be to set the blend to go sideways (the 8 ½” direction– left to right) of the bar, where the blend has more distance to travel. This extra distance will allow for a smoother transition if you want to graduate from 100% to 3%. The safest alternative is to create your gradation in Photoshop at 300 dpi and add 2 to 5 units of “noise”. This makes a much larger file, but it will be less likely to band.
Another secret to graduations is to NEVER graduate to 0%. You will get more banding if you do. This is because imaging devices such as imagsetters and platesetters have difficulty with interpreting a 0% screen. Instead, stop your graduation at 3% (or higher).
Proofing graduated screens can also be difficult. First, what looks great on your computer monitor may not look so great when output at a greater resolution for print. Also, a laser printer will image a screen much differently than a printing press. This is because most laser printers apply images using a continuous tone or some sort of proprietary technology. Graduated screens are, after all, about screens. If your laser printer cannot produce accurate screens, it will give you an inaccurate idea of how they will look on press.
Finally, proofs cannot replicate the amount of “dot gain” that occurs when ink meets paper. In fact, many laser printers can be very misleading on dot gain. This is due to the fact that 1) laser printer inks don’t replicate the same absorption characteristics as printing inks and 2) one usually does not laser on the actual stock that is being printed on. Dot gain has a major effect on how graduated screens look once they are printed. The more dot gain you have, the more “plugging” you will get in the screen. Be particularly aware of this when printing graduated screen on uncoated paper.