UCR

/juː siː ɑːr/

General Definition

UCR is an advanced technique in the Color Separation process used when converting color models like LAB or RGB to the printable CMYK color space. The primary goal of UCR is to reduce the values of colored inks (Cyan, Magenta, Yellow) in the image’s dark areas (especially in shadows and black regions) and replace them with Black ink. This process is executed to reduce the Total Ink Coverage and enhance print stability. UCR ensures that dark areas achieve the deepest possible density with the minimum amount of colored ink consumed. The acronym UCR is also known in the printing and packaging industry as Under Color Removal and Under Color Reduction.

Real-World Usage

The UCR mechanism is only applied to colors that consist of a combination of all three chromatic inks (CMY), such as gray shadows or neutral colors. Colors made up of only one or two primary inks (such as pure Cyan or a pure Red from Magenta and Yellow) are not affected by this process. This distinction is crucial, as UCR prevents unintended color shifts in vibrant and primary colors, focusing solely on the stability and depth of complex dark areas.

The use of UCR is directly related to the physical limitations of the printing press. By reducing CMY values in dark areas, UCR helps limit the Total Ink Coverage to values such as 300% or 330%. This ink coverage limit is a direct result of using UCR. Ink coverage above this limit can significantly prolong drying times, and very thick ink layers can crack, especially during paper folding or post-press operations. This method is typically applied through the ICC Profile in the lithography software.

Consultant's Note

As a production consultant, it is suggested that, you view UCR as a quality assurance tool for the printing process. The correct use of UCR is essential for maintaining the stability of gray tones and shadows. If your client demands high depth and uniformity in dark colors, UCR allows you to provide that depth with lower risk (faster drying, reduced set-off risk). Ensure that UCR settings are a fixed and unchangeable part of your standard print shop ICC Profile.

Understanding that UCR is an unchangeable process at the profile level is vital for your Color Separation team. This means you cannot change these settings on the fly after producing the plates or films. The ultimate goal is to achieve maximum visual quality and physical stability (such as resistance to cracking in lithography) by carefully managing UCR, while simultaneously optimizing ink consumption and drying time. For better control in color adjustment and consistency across the entire tonal range, our final recommendation is to use the GCR method.

Aligned with: Adobe / Idealliance / ISO 12647