ONYX Profiling Engine - ICC Build Options

Overview Description
This document outlines the options within the ONYX ICC Build dialog. These definitions explain the different settings and why you may choose to edit the defaults when building ICC profiles depending on your output.

Predefined

• Custom - Use "Custom" to change the default settings. If you do not choose a predefined setting, the dialog automatically defaults to Custom.

Note: Based on some initial testing, following are some additional predefined settings for the black generation and total ink limiting.

• Inks with Light Black (k) - This tells Media Manager that the printer has an ink set with light black and allows us to start adding black earlier. Hence, the Start Black is set to 0.
• Inks with Light Cyan (c) and Light Magenta (m)- This setting tells Media Manager that the printer has an ink set that contains both c (light cyan) and m (light magenta) and sets some limitations on starting black earlier.
• No Light Inks - This setting allows you to set the Start Black lower which begins adding Black to CMY a little earlier.

Note: Remember that these settings were created based upon color theory and you might need to change them as you test on different printer and media combinations. We may also introduce additional predefined settings as we learn the best configurations for specific modes.

Table Size

• 41-Point Grid - When output accuracy is of prime importance, users should opt for the 41-Point Grid setting. This is the default setting.
  Note: This option determines the size of the output table in the printer profile. The accuracy of the profile, and the size, increases with the number of grid points (steps in the table). It also takes longer to build a larger table.
• 33-Point Grid - The 33-Point Grid setting is acceptable in the majority of cases.

ICC Profile Version

• Version 4.x - The ICC introduced this new profile specification in 2001 and this is the default option. As the latest specification, it has numerous improvements over earlier version in terms of flexibility and interoperability with other vendor profiles. Profiles built with ONYX comply with all of the 4.x specifications, but not all application support 4.x profiles so you may not be able to use them with third party applications.
• Version 2.x - This ICC specification is older and uses a different encoding which was less defined. This means that the same ICC profile could be interpreted differently depending on the CMM used.  Most application support 2.x for viewing and implementation as an input profile. If your third party application does not support 4.x than you must build the ICC using 2.x.

Note: Both 4.x and 2.x use 16-bit tables. ICC profiles built using the ONYX ICC Profile Generator can be used outside of the program or as an input profile in a proofing workflow. This complies with the current end-user agreement license. 

Viewing Light Source

This option is only available if you use a Spectrophotometer to read swatches. This allows building an ICC profile for target lighting other than D50. The following is a list of standard Illuminants specified by the CIE (Commission Internationale de l'Éclairage) - International Commission Illumination:

• Lighting A - This represents an incandescent light source like a tungsten filament.
• Lighting C - Represents average daylight.
• Lighting D50, D65, D93- The D-series illuminants represent different times of the day in an outdoor setting. D50 is a standard for Graphic Arts Industry. As the number increases from 50-93 the light gets more bluish (i.e. more bluish component is present).
• Lighting: F1, F2, F3, F4, F5, F6, F7, F8, F9, F10, F11, F12 - These are the fluorescent light simulators.
  • F2, F7, or F11 Illuminants - These illuminants simulate most indoor lighting.
  • F2 - Represents a typically cool white fluorescent source.
  • F7 - Represents a broad band daylight fluorescent source. Examples of F7 are GE and Philips daylight fluorescent sources.

Note: D50 is the default setting for the Graphic Arts Industry.

Generally, if you know the type of lighting and the brand of the bulb you use to view the print, you can obtain the information from the manufacturer about the CIE standard illuminant they are simulating (http://www.cie.co.at/cie/). Then you can use that illuminant to build the profile. If the print will be viewed outdoors, then using either D50 or D65 is appropriate.

Gamut Mapping (Affects Perceptual Rendering Intent Only)

• Classic Gamut Mapping - Classic gamut mapping is the standard strategy for most users as it produces a maximum output gamut. This is the default setting.
• More Lightness Preserving- This gamut mapping strategy is best used when printer, ink, and media combinations produce a smaller gamut. This may be the case if Ink Restriction settings were set lower than typical. This strategy corrects for light colors, specifically yellow and lighter areas of the output gamut, where the color may appear dirty.

Use Large Input Profile Size

• This option is similar to the Table Size option except it allows users to build a bigger input table. The input table is used only when the profile is used as an input profile within ONYX for CMYK based images or in proofing workflows.

Note: This setting is enabled by default. If the profile is intended to be used for proofing, using a large input table is recommended. It increases the accuracy of the transform.

Balance CMY Gray

• Checking this option makes sure that a neutral gray is obtained using the optimal levels of CMY inks.

Note: This setting is enabled by default.

Improve Profile Interpolation

• Interpolation improves the accuracy of the boundary points within the gamut.
• It will helps expand the gamut by pushing out the boundaries and makes the edge points smooth.
• This is not based on any pre-defined model, our color scientist have developed this new modeling for more accurate mapping.

Note: This setting is disabled by default because the processing takes longer to build. 

Dynamically Generate Ink Separations

• Innovative Dynamic Ink Separation technology improves the utilization of special printer inks.
• ICC profiles can now be generated for CMYK + Spot(s) configurations.
• This options is not used when profiling white ink because white is not a Chromatic color. See Chroma.
• Ink Separations are used to specify how to use Hifi inks or chromatic spots.
  • e.g. DUPONT Artistry w/ CMYK + V.
  • Chromatic Spots as seen in textile, packaging, and specialty printing.
  • See new ICC Build Option when working with unknown spot channels.
• When enabled this feature uses measurement data to determine maximum chroma ink separation.
  • This feature will always be available for profiling with spot colors.
  • This feature is not available if a Hifi color mode is not being profiled.

Note: This option is only displayed when profiling a CMYK+ ink configuration. In all other cases, users will not see this options.

This option is intended for users who are profiling a print mode that uses an ink sets with uncommon spot channels, i.e. CMYKXYZ (where XYZ is not OG or RGB). When this option is enabled, the software figures out what the color is and how to separate the channel dynamically to get the maximum chroma. For example you could have a CMYKSS print mode and use Red and Purple in the spot channel and the software will allow you to generate an accurate profile based on patch readings by mixing the spot channels into CMYK. The nice thing about this feature is you don't need to create a custom ink configuration, you can choose CMYKSS and profile as normal.

Dynamically generated ink separations can be used for profiling as an option instead of our predefined static ink separations (for Hifi ink configs). In most cases you will see little gain in gamut if you use this option with CMYKRGB and CMYKOG. If you choose to use this option the results should at best be the same as our pre-defined static separations that are used with the option disabled. Generally the static separation give CMYKRGB and CMYKOG the best smoothness utilizing the pre-defined modeling.

It is not recommended to use this option with low gamut media. You can tell if you have a low gamut media during the Ink Restrictions step if your settings are very low because you're not putting enough ink on the paper to get a large gamut. This can happen if you have ink/media compatibility issues.

Total Ink Limit

• This slider allows you to adjust the total ink limit within the ICC profile. Usually done after the initial build - see note below.
• The default setting for a 4-6 color printer (CMYK, CMYKcm) is 400%.
• The default setting for a CMYKRGB printer is 700%.

Note: The number displayed as the total ink percentage changes depending on the number of ink channels being profiled. If the ICC profile displays saturation issues on the test print, you can lower this value 5-10% to reduce the ink load. You must to rebuild the profile to accept the newer settings.

Black Generation - GCR (Gray Component Replacement)

GCR - Gray Component Replacement. We are controlling how much black ink to add used based upon a grayscale CMY ink image. The start point is the point relative to CMY ink where black ink is added. If there is any removal of CMY it is due to an adjustment of Total Ink.

There are two (2) separate GCR controls for the output gamut. They are separated into Achromatic and Chromatic regions. The two controls do not compete with each other, but work in combination for overall GCR control.

• Achromatic - The Achromatic section controls the neutral colors (i.e. gray C=M=Y).
• Chromatic- The Chromatic region includes the non-gray gamut surface colors (i.e.C≠M≠Y highly saturated colors, those found in the outer lower regions of L*a*b*).
  Note: This ONYX exclusive feature gives the user total control over the gamut size achievable with Black Generation.
• Start Black - Start Black is where "black" (K) is introduced into the color mix (CMY).
• Maximum Black - Maximum black is set to 100.
• Black Generation - Black Generation determines the "curve" or the rate at which black is added into a particular gamut region.
  • MaxK is the most aggressive.
  • NoK will not use any black.
  • Moderate is the default and is closest to a traditional GCR 3 setting.

Black Generation Tips

• If you want your gray colors to include more black, lower the Achromatic value and use a more aggressive curve.
• If you want the darker, more saturated colors to include more black, lower the Chromatic value and use a more aggressive curve.
• Having a lower start black for chromatic region allows us to achieve dark saturated colors increasing the gamut size. But this might not be always desirable so we can increase the Start Black only for chromatic region without compromising the neutral darks.
• The Black Generation default settings are:

• Achromatic = 50.
• Chromatic = 65.
• The default curve for both is Moderate.

Why do we use Black Generation for building ICC profiles?

In an ICC profile there are two tables that convert color between device space (printer inks) and device independent space (LAB). If we have a printer with CMYK ink, the conversion from L*a*b* to CMYK becomes a little tricky because an L*a*b* value can be generated using different combinations of CMY and K but only one combination needs to be used. The aim, usually, is to get as big a gamut as possible. But having a really big gamut is not always desirable because this might introduce peppering into the lighter areas. Black Generation gives you the additional control to prevent these issues.

By selecting a particular Black Generation setting, we are pre-selecting a specific "recipe" to move from L*a*b* to CMYK as well as selecting a specific Gamut Mapping strategy, too.

The Start Black value determines when to start adding black ink into the CMY combination. For example, let's say that the Start Black selected is 50. This ensures that there is no black ink present when the minimum value of CMY is below 50. So, CMY patch values like (49, 49, 49), (49, 58, 75), (40, 100, 90), (0, 100, 100) will have 0 black, because the lowest of these values is below 50.

In the ICC Build Options graph, the x-axis is this minimum CMY value and the y-axis is the black ink that we will get for that minimum CMY with the corresponding settings of black generation.

Black Generation - UCR (Under Color Removal)

UCR - Under Color Removal. We are controlling how much CMY ink to add based upon a grayscale Black ink image. The start point is the point relative to black ink where CMY ink is added. (Not adding CMY ink is equivalent to removing it.)

This method of black generation that uses black only in the neutral and gray areas, which is why the selection is only available under Achromatic. When you enable this check box the opposite rules apply. With GCR you start with CMY values and introduce black and a certain percentage. With UCR you start with only black and introduce CMY and a certain percentage. The curves also work in reverse as seen on the graph.

Using UCR helps to improve gray balance and Metamerism and is mostly used when creating black and white output. Depending on the printer technology, it may produce more course output in the lighter areas and overall you're going to use a little less ink.  From a distance you get better neutrality and contract.

Prints will look more grainy because you're taking away what GCR gives you in smoothness. GCR removes that black ink in the lighter areas and replaces it with CMY and because the contrast between the black ink and the colored inks is less it becomes less noticeable. A black dot on white paper has more contrast regardless of the size of the dot.

When to use GCR and UCR simultaneously?

The best reason to use both is when you intend to print black and white images (photo) or if your printer uses a light black ink. You want your light gray areas to be stable and not color shift while also keeping your 3 color light areas in an image uncontaminated with black dots which will result in "peppering".

• When the UCR option is checked - it is ONLY being applied to the Achromatic Black Generation. (This method is not used for Chromatic Black Generation in any scenario).
• When the GCR option is checked - it is being applied to the Chromatic values within the profile and is the traditional method for Black Generation.
• Using both allows you to control Neutral gray and Saturated colors separately.
• When ONLY the GCR option is checked, it will apply the method (CMY, then add K) to both Achromatic and Chromatic values.
  

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