AM Screening

/eɪ ɛm ˈskriːnɪŋ/

General Definition

AM Screening (Amplitude Modulation Screening) is the standard Screening method in the printing industry, operating on the principle of variable dot size. In this technique, the screen frequency (LPI) and the screen angle are fixed, but the size of the halftone dot changes proportionally to the required color tone. This technique is the foundation of traditional and modern Lithography printing. The relative simplicity of this model makes it the most widely used method, but it is prone to generating Moire in high-density color areas.

Real-World Usage

In the production environment, AM Screening is managed by the RIP software. This software converts image data into a regular screen pattern (Fixed LPI) and sends the information to the CTP device for imaging. This process ensures that the halftone dots are created with the appropriate size and accuracy to reproduce gradients. The main advantage of AM is the simplicity of controlling Dot Gain and its compatibility with common printing machines, which helps keep costs manageable.

One of the key disadvantages of AM Screening is the limitation in very fine visual details and the potential for Moire generation. For this reason, in extremely high-quality work, its competitor, FM Screening is preferred. FM changes the dot density (Frequency) instead of the size (Amplitude). However, given its stability and predictability, the final quality in AM Screening can be checked by analyzing the dot structure, which often forms a visual pattern known as the Rosette.

Consultant's Note

As your consultant, I recommend that, you always consider the job's final requirement when selecting the Screening type. AM Screening is a reliable workhorse, but you must know its limitations. For jobs involving uniform colors and standard images, AM offers the best combination of quality and efficiency. However, if you require the output quality of FM Screening, you must ensure your CTP device has ultra-high DPI output capability, and your personnel have sufficient RIP management knowledge for that screen type.

The key point in AM Screening is the correct management of the Screen Angle. These angles must be precisely set to prevent visual interference and the creation of Moire. Your Prepress team must work with standard printing profiles (such as G7/ISO) that define these angles optimally. Using this method in most commercial cases is the most cost-effective and stable way to achieve quality halftone output in Lithography printing.

Packdemy Council Insight

Derek Peacock

Strategic Advisor

AM screening (Amplitude Modulation screening) is the conventional halftoning method in which dot spacing remains fixed while dot size varies to reproduce tonal values.

In real production environments, AM screening is widely adopted because of its predictability, tolerance to press variation, and compatibility with established workflows. Larger dots in midtones and shadows provide mechanical stability, making the process more forgiving on absorbent substrates and high-speed presses. However, AM screening introduces structured dot patterns and fixed screen angles, which can create moiré interference when separations are improperly aligned.

From a consultant’s perspective, AM screening must be engineered through careful selection of screen ruling (LPI), screen angles, and dot shape relative to substrate and imaging capability. Excessively high LPI beyond plate or press stability leads to tonal compression and dot gain inconsistency.

Advanced control involves matching screen ruling to substrate absorbency and viewing distance. AM screening is effective not because it is traditional, but because it can be standardized and repeated reliably across industrial environments.