ICC RENDERING INTENTS
Introduction to Rendering Intents
Different devices have different ranges of possible colors (different color gamuts), and often have different paper colors or white points. This creates special problems for color matching. The four rendering intents defined by the ICC are essentially "matching styles" that address these issues in different ways. You can read more about color gamut and mapping at What is Color Gamut and Gamut Mapping?
The Microsoft ICM2 (Linotype) color management engine built into Wasatch SoftRIP allows rendering intents to be specified. Recent revisions of Wasatch SoftRIP make informed decisions regarding default settings of rendering intents. When importing data for "general" printing, SoftRIP defaults to the Perceptual rendering intent, and when importing data for "proofing", the default is to the Relative Colorimetric rendering intent.
For those whose needs are not met by these defaults, controls are available so that users can make their own choices. This kind of control can be critical for precision color proofing and gicleé printing.
The discussion below describes the four rendering intents defined by the ICC, along with defaults and recommendations for use within Wasatch SoftRIP.
This rendering intent maps color smoothly, preserving relationships between similar colors. This prevents gamut clipping, with its potential loss of detail and "tonal banding" problems. Gamut clipping occurs when colors that are different in the input image appear the same when printed. The Perceptual rendering intent makes small compromises throughout the entire color space in order to preserve color relationships. It sacrifices some precision of in-gamut colors in order to ensure pleasing results. Click here to see what a gamut clipping problem looks like.
The Perceptual intent will produce the most predictable results when printing from a wide range of image sources. For example, when printing RGB images on CMYK devices, or when trying to match CMYK devices that are radically different from each other. We consider this "foolproof" setting to be best for users who handle the wide variety of images that commonly enter large format printing facilities. It is usually not precise enough for processes where input images are well controlled, such as color proofing and gicleé. The Perceptual rendering intent is the setting of the default color configurations shipped by Wasatch. It is also set by default whenever ICC data is imported by Wasatch SoftRIP in "non-proofing" mode.
When a color is not printable within the gamut of the output device, this rendering intent simply prints the closest match. It reproduces in-gamut colors without compromise, as faithfully as possible. This produces the most accurate matching of spot colors. Unfortunately, it can also result in gamut clipping where two colors that are different in the original are identical on the print. White points are similarly clipped, which tends to cause similar color relationship problems in the highlights of images. Such clipping, and the resultant problems, make this choice generally unsuitable for work involving anything but spot colors. Although Wasatch SoftRIP never sets it as default, you can choose it from Wasatch SoftRIP's user interface.
When a color is not printable within the gamut of the output device, this rendering intent prints the closest match along with an adjustment that maps white to the paper of the output. This white point mapping prevents the problems of Absolute Colorimetric when images (or anything other than spot colors) are involved. When producing color match proofs on inkjet printers, which typically have larger gamuts than the printing presses being simulated, this is a superior choice. When a pair of ICC profiles is loaded for run-time linking, one for the device to be simulated and one for the device being used, this rendering intent will provide good precision (minimal delta-E) for the match-proof process. This is set by default by Wasatch SoftRIP whenever ICC data is imported for proofing with input/output ICC profile-pairs.
This preserves the saturation, or brightness of colors when transforming them for output. It maps fully saturated source colors to fully saturated target colors. This rendering intent is used where color matching and exact relationships between colors is less important than bright colors. This is a "pretty picture" intent that will produce brilliant spot colors, and although Wasatch SoftRIP never sets it as default, you can choose it from Wasatch SoftRIP's user interface.
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