Troubleshooting Color: Output Color Profiles

More than once I have been asked: "OK, so the color is wrong, how do I make it right?"

Troubleshooting CMYK color can be a pain, because there are often many places the problem could be lurking, and changes made in one, may inadvertently alter the output based on info from another. So in this five part series, we will look at five important steps to troubleshooting a color managed system, or colorimetric tuning.

As you all know, a color management system is usually broken into five parts:

1. Source color space
2. Media parameter setup
3. Source color space designation
4. Output color profile
5. Output calibration set

Let's take a look at number four on our list - Output Profiles

One of the first things to be aware of is your own expectations. People often assume that printer profiles should make everything match but a printer profile is just a measurement of what a combination of printer, ink and paper can reproduce.

Different types of printers and ink sets will produce different color gamuts. Different papers and surface textures will influence both color gamut and appearance. Matte papers always look flatter than gloss papers for example. Also the color of the paper white has a big influence. A warmer paper color will give warmer grays and skin tones than a cooler more blue-ish white paper.

Media with Optical Brightening Agents (OBAs) often require custom profiles to account for the fluorescing factor.

The combination of the ICC output profile and the calibration set allow the RIP to adjust for the white point, imaging characteristics and d‐max capability of the output media. For standard color, the output profile may have less effect on color than does the calibration set and other factors described previously. Bypassing conversion always ignores output profiles.

In most cases, the standard Fiery output profiles for Plain, Coated Matte & Coated Gloss may be suitable for most customers on most media. These are based on GRACoL standard, therefore are neutral grey by default.

After machine setup and linearization, the machine should be calibrated on the target media and test prints made using the applicable standard Fiery profile. Only if results appear unacceptable or sub-optimal should the time be spent to create custom output profiles.

If a custom output profile is necessary, the standard 928 patch target seems to provide suitable results on most printer/copiers. I advocate the use of an iSisXL spectrophotometer to reduce the time and effort to read the test patch pages. Otherwise, an ES‐1000 or ES‐2000 can be used within a Fiery RIP, or an XRite spectrophotometer for external software, but of course, using a hand-held device takes more time.

In some cases, the profiles being used in Photoshop may not be the same as the profiles on the RIP controller. One example of this is if the USWebCoatedSWOP profile is being used in Fiery Creative Suite with a newer RIP controller that has the SWOP2006_Coated3 profile installed from the factory. In these cases, you may import the profile you are using for the working space definition in Creative Suite onto the RIP's controller so it is available in Color Setup.

Another example is if you are using a custom press profile for a conventional press and need to match the RIPs color output to that press.

If your inkjet is driven by RIP software then part of the calibration and profiling process is setting the printer options, ink limiting and linearization and it is with these that the root of most problems can be found. Getting the printer options right for any media can take a while, factors such as the number of passes, resolution, head height and drying times all can have a big influence on the print. Again the media manufacturer should be able to guide you.

Specific settings that may help:

Optimized: Creates custom calibration d‐max calibration targets as read from the profile test patch page(s). 
This setting should generally be left ON, which is the default for most printer/copiers. Only the d‐max endpoint is read from the target. The intermediate curve is calculated using a general formula and does not follow any unique density variations in the printer/copier.

Black Generation: Specifies toner limit and GCR parameters. 
Specifying a black toner maximum of 95% instead of the default 100% will provide a smoother tone and gloss generation in the deep shadows. If designated at 95%, TAC reaches a 180‐260% value in the shadows, while designating at 100% usually causes a TAC drop to about 130%. Using the 95% black specification prevents a gloss roll‐off in the shadows on some media, while using the 100% black specification may reduce total toner usage. 

95% is usually recommended for best image quality. A TAC (Toner Limit) value of 260% should be used. Default values for Ricoh printer/copiers in CPS Ver 3 and Ver 4 may default to either 400% or 270% dependent upon the revision. 

Very aggressive GCR settings may reduce banding and total toner usage dependent upon the colors found in the source job. Changes to other parameters may be used for specialized purposes.

----------

Do you have a color management question, horror story or event to share?

Email me at reilley4color@gmail.com

Troubleshooting Color: Source Colorspace Designation

More than once I have been asked: "OK, so the color is wrong, how do I make it right?"

Troubleshooting CMYK color can be a pain, because there are often many places the problem could be lurking, and changes made in one, may inadvertently alter the output based on info from another. So in this five part series, we will look at five important steps to troubleshooting a color managed system, or colorimetric tuning.

As you all know, a color management system is usually broken into five parts:

1. Source color space
2. Media parameter setup
3. Source color space designation
4. Output color profile
5. Output calibration set

As we have discussed, the source colorspace is crucial to determining how the system should translate from the input color to the output color, via command given to the rendering engine. Without knowing where you start from, it is difficult to navigate where you wish to be.

The color space and variant used to create the job must be designated in the RIP's job parameters. If you know with certainty the input color space, you can define it explicitly. If you do not have this information, most operators use sRGB, since it is the smallest of the RGB input color spaces, and thus the lowest common denominator.

Most RIPs allow you to recognize if a given file has input profile information embedded in the file. If present, this information gives you the best chance of output that matches what the file's creator intended.

Almost every file has some CM information present. Even if the original creator of the file was not prepress proficient, Adobe Creative Suite automatically embeds color input info when saving files. Should someone convert from RGB to CMYK in Photoshop, for example, the file is now in GRACoL CMYK, since that is Adobe's default. Honoring this embedded information is the best way to ensure you are printing to the original creator's intent. It is up to the operator to ensure that this embedded data gets honored.

The easiest and most consistent way to do this is the Use Embedded Profile When Present selection in the color setup tab of the job's parameters which is only effective when the job contains an embedded tag/profile. This is usually the first item to check when printed colors are significantly different than expectations. 

A few troubleshooting hints:

• AdobeRGB jobs printed as sRGB appear flat.
• sRGB jobs printed as AdobeRGB appear too dense with high chroma.
• Flesh tones in GRACol/SWOP jobs printed as ISO (System 7 default) appear rather sun burnt.

----------

Do you have a color management question, horror story or event to share?

Email me at reilley4color@gmail.com

Troubleshooting Color: Media Parameter Setup

More than once I have been asked: "OK, so the color is wrong, how do I make it right?"

Troubleshooting CMYK color can be a pain, because there are often many places the problem could be lurking, and changes made in one, may inadvertently alter the output based on info from another. So in this five part series, we will look at five important steps to troubleshooting a color managed system, or colorimetric tuning.

As you all know, a color management system is usually broken into five parts:

1. Source color space
2. Media parameter setup
3. Source color space designation
4. Output color profile
5. Output calibration set

Part 2 - Media Parameter Setup

There are many different kinds of paper, such as recycled and rag paper for newspapers, glossy coated paper for magazines, uncoated paper for stationary and bright-white coated paper for high-quality brochures. Some paper is coated for a particular ink, some has already been printed on (shells) and some is in fact black, or darkly opaque for printing on a 5th color station press, using white toner. And now synthetics have become a hot trend in digital printing.

As you can imagine, each type has different characteristics when it comes to printing. The recycled paper sucks up more ink, and if you don’t take this into account, your beautiful full-color photos will become too dark, and the ink will blur over the paper, creating an ugly brownish effect. Coated paper reflects light differently, and distinction between matte & gloss can make a LOT of difference to the final colors.

So, how do you optimize artwork for all of these different kinds of papers? Well, that’s the easy part. 

Standard CMYK inks have been tested on every type of paper imaginable. The way cyan, magenta, yellow and black are printed on a specific type of paper is documented in an ICC profile (a complete record of a print device's color gamut). All you need to do is download these free “Color Profiles” and select the right one when you export a PDF using InDesign (Export → Output → Color Conversion & Destination). 

In Photoshop you can use these profiles as input profiles, to soft-proof colors printed on specific stock.

To learn more about profiling, read Calibration and Profiling

The RIP's job parameters related to media setup and imaging style must be consistent for the customer’s job, as well as for the related profile generation and calibration pages. 

A specific determining factor is Fuser temperature: Higher fuser temperature results in increases in gloss and density.

The primary specification for fuser temperature is Paper Weight, with a lesser degree of control through paper type (Plain, Glossy, Matte). Fuser Nip (dwell) and direct Fuser Temperature setting in the paper catalog entry also have an effect on fuser temperature.

Halftone Mode: Also known as screening type. Specifies whether line or dot screening is used, and in
some print devices, the halftone resolution (lpi) and native resolution (600 or 1200).

Resolution: Effective pixel addressability, collected pixel size and gray tone possibilities. May be
specified combined with Halftone Mode.

These job properties must be decided upon prior to any further color tuning, and used for all customer
jobs, calibration sheets and profile targets for the applicable job/media setup. Of course, any given
machine and customer may use one or more job/media setup with varying parameters.

Any adjustments determined in Print Engine Setup should be applied via SP mode and/or a paper
catalog entry and used for all applicable prints.

----------

Do you have a color management question, horror story or event to share?

Email me at reilley4color@gmail.com